-------
California
Implications
The potential change in seasonality of runoff could have
significant implications for stream ecosystems and the water
resource system in the Central Valley Basin. Reduction in
streamflows in the late spring and summer could negatively affect
aquatic organisms simply because of decreased water volume.
Wildlife using streams for food and water also could be harmed.
Water quality probably would be degraded because pollutants could
become more concentrated in the streams as their flows decrease.
The possible impacts on the water resource system are discussed
in the next section.
The decrease in spring, summer, and fall soil moisture could
have a strong impact on the vegetation in the basin, with plants
adapted to drier conditions becoming more abundant at the expense
of plants adapted to higher moisture conditions. These potential
vegetation changes also could affect wildlife, and perhaps water
quality, through changes in the nutrient .composition of upland
runoff and changes in erosion rates.
Water Resources in the Central Valley Basin
Changes in runoff under the different climate scenarios
could have a major impact on the water resources in the Central
Valley. The study by Sheer and Randall (Volume x) was designed
to use estimates from Lettenraaier et al. of streamflows into the
Central Valley to simulate how the water resource system would
perform under these conditions. Particular importance is given
to how water deliveries to users would be affected by climate
change.
Study Design
Sheer and Randall used an existing model of the water
resource system of California that is currently used by the
Metropolitan Water District (MWD) of southern California to
estimate the impact of the climate scenarios on water deliveries
(Sheer and Baeck, 1987). The model emulates the State of
California's Department of Water Resources Planning Simulation
Model (California Department of Water Resources, 1986). The
model used hydrologic inputs to project water use demands,
instream and delta outflow requirements, and reservoir operating
policies. Water demands were set at levels projected for 1990.
Two different sets of runs were made with the model. The
first involved running the model for the different climate
scenarios using current carriage water requirements. Williams
4-22
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Chapter 4
(see Salinity in San Francisco Bay section of this chapter)
determined that in response to rising sea level and levee
failure, carriage water might have to be doubled to maintain the
water quality at the delta pumping plants (see Figure 4-2).
Consequently, Sheer and Randall ran the model a second time to
determine the effects of doubling the carriage water requirement
on water deliveries. Both simulations were run with a monthly
time step, with water deliveries summarized on a yearly basis.
Interannual variation is used as an indicator of reliability of
delivery.
Sheer held a meeting with representatives of the State
Department of Water Resources and the Bureau of Reclamation to
discuss the results of his analyses and to get their response on
how the water resource system would handle the changes in runoff.
Limitations
The limitations to Lettenmaier's study carry over to this
one. Thus, interpretation of the results of the simulation of
the water resource system's response to climatic change should
focus on how the system deals with the change in seasonality of
runoff, rather than the absolute values of the model output.
Also, the model was run using 1990 conditions, and changes in
future management practices, operating rules, physical
facilities, water marketing, agriculture, and demand are not
considered in the simulation.
Results
The simulation results suggest that both the amount and
reliability of water deliveries could decrease after global
warming. The decreases in mean annual SWP deliveries range from
7% (OSU) to 14% (GFDL) to 16% (GISS). In some years, the
decreases are over 20% for all three double C02 scenarios. The
projected decrease in water deliveries occurs despite a slight
increase in precipitation over current levels in the climate
scenarios and greater total outflow from the delta. Average
monthly outflow from the delta increases in the late fall and
winter under the climate scenarios and is lower in the spring
(Figure 4-7).
The driving factor behind this decrease is the change in
seasonality of runoff. Higher winter temperatures would lead to
more of the winter precipitation in the mountains falling as rain
rather than snow, and also to an earlier melt of the snowpack.
Consequently more water would flow into the system early in the
rainy season. Given current operating rules, the current
4-23
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California
reservoirs would not have the capacity to store the early runoff
and at the same time retain flood control capabilities. Thus, in
the simulation, much of the early runoff must be released,
resulting in less water in storage at the end of the rainy season
and lower water deliveries during the dry summer months. With
system changes, it would be possible to store the extra runoff.
The shift in the seasonality of runoff and the response of the
water resource system to that shift drives the changes in monthly
delta outflow (Figure 4-7) .
Doubling the carriage water requirement in the model run for
the GISS scenario only minimally affects SWP deliveries. This is
because the baseline period (1951-80) does not include a lengthy
drought period, during which the doubled carriage water
requirement could have a substantial impact on deliveries.
The consensus of the meeting of the representatives from the
State DWR and the Bureau of Reclamation concerning the potential
changes in the seasonality of runoff is that the magnitude of
this change is such that operational changes alone would not
markedly improve the system's performance. One factor limiting
the potential for adjusting the system to the projected changes
is the likely need to provide for additional flood control
storage during the winter months because of higher peak flows.
Implications
Under the three double C02 climate scenarios, water
deliveries are less than the base case and could fall short of
1990 demand. Moreover, if carriage water requirements.are
doubled, shortages during a prolonged drought could become more
significant. In addition, users and managers project a water
demand of 3.6 million acre feet (maf) by 2010 (California
Department of Water Resources, 1983). This demand could not be
reliably supplied under the current climate and resource system,
and the shortage might be exacerbated under the three double C02
scenarios. The potential decrease in water deliveries could
affect urban, agricultural, and industrial water users in the
state. How the potential decrease should be managed has many
policy implications, which are discussed at the end of this
chapter.
On the other hand, the increase in delta outflow shows that
more water could flow through the Central Valley Basin under
these scenarios, and water deliveries could be increased if major
new storage facilities were constructed. However, this would be
an environmentally and politically controversial option (see
Policy section).
4-24
-------
OO
120
)00 -
80 -
60 -
40 1
.20 -
00
I
NOV
BASE
DEC JAN
GFOl
FEB MAR APR
MONTH
MAY
JUN JUL AUG SEP
GISS
OSU
Figure 4-7.
Projected monthly Delta Outflows under Different
General Circulation Model Climate Scenarios.
Source: Adapted from Sheer, Volume .
4-25
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California
Salinity in San Francisco Bay
Climate change could affect the San Francisco Bay estuary in
two ways: first, changes in precipitation and temperatures could
affect the amount of freshwater runoff that will flow into the
bay; and second, global warming could cause sea level to rise
because of thermal expansion of the water and glacial melting,
which could in turn affect a wide range of physical
characteristics in the bay. The major objective of the study by
Williams (Volume x) was to estimate the implications of global
warming and rising sea level on the size and shape (morphometry)
of the San Francisco Bay estuary and on salinity in the estuary.
Study Design
Williams' project was conducted in three parts, using two
sea level rise scenarios and delta outflows estimated by Sheer
and Randall (Volume x). The sea level rise scenarios are a 1-m
(40-inch) rise with the levees in the Sacramento San Joaquin
Delta and San Francisco Bay proper maintained, and a 1-m sea
level rise with levee failure. The first part of this study
involved estimating how sea level rise would affect the shape of
the bay by establishing the elevation/area and elevation/volume
relationships for all areas below +3m (+10.0 ft) according to
National Geodetic Vertical Datum (NGVD). Then the tidal exchange
characteristics for the bay were determined for its future shape
by using a tidal hydrodynamic model (Fischer, 1970).
Finally, the salinity in the bay under the combined impacts
of sea level rise and changing delta outflows was calculated by
using a mixing model developed by Denton and Hunt (1986). This
model was run first with nine different constant delta outflows
(all months the same) to establish new carriage water
requirements after sea level rise. Once these were established,
and Sheer and Randall (Volume x) had run their simulation model
with the new requirements, the mixing model was run again to
determine the salinity regime in the estuary after climatic
change. Included in the model output are average monthly and
average annual salinities in different parts of the estuary under
the different scenarios.
Limitations
Because of the short time frame, Williams used some old and
inaccurate surveys in the morphometric analysis instead of making
new surveys. These could produce errors of plus or minus 20% in
the estimates of the estuary's volume. In addition, some levees
probably will be maintained under any delta management plan, and
4-26
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Chapter 4
thus the flooding of the delta islands would not be as extensive
as assumed in the levee failure scenario. Williams did not
consider changes in siltation and erosion of sediments that would
likely occur under the different climate change scenarios.
However, erosion would probably have a significant impact on
water flow in the delta. For instance, deepening of the tidal
channels in the delta could lead to intrusion of salinity farther
upstream than projected in this study. In addition, more
sophisticated models of salinity and tidal ranges and exchanges
might improve the accuracy of the results. Finally, the new
carriage water requirements were based on a steady-state analysis
(e.g., constant delta outflows). Changes in the hydraulics of
the Sacramento, San Joaquin delta and Suisun Bay with sea level
rise could increase these requirements. Williams' results should
be viewed as a preliminary estimate of estuarine changes, with
emphasis placed on the direction of change, rather than on the
absolute amount of change.
Results
The morphometric analyses suggest that given.a 1-m (40-inch)
sea level rise and failure of the levees, the total area of the
estuary might triple, and its volume could double. If the levees
are maintained, the increases in area and volume could be about
30 and 15%, respectively (see Figure 4-2). Interestingly, the
amount of sea level rise is less important to the physical size
of the bay than whether or not the levees are maintained.
Under the sea level rise scenarios with levees maintained,
tidal ranges do not change significantly from current conditions.
If levees fail, downstream constrictions at Carquinez Strait and
to the east of Suisun Bay (see Figure 4-2) limit tidal transport
and reduce tidal range in the delta, assuming that erosion does
not alter the tidal characteristics of the delta.
The results from the initial application of the salinity
model to constant delta outflows indicate that monthly carriage
water requirements might have to be doubled to repel saline water
from the upper part of the delta. Also, whether or not the
levees are maintained has little effect on the salinity regimes
in the bay according to the model's results. However, because
possible scouring of tidal channels is not incorporated into the
model, the predicted salinity after levee failure is probably
underestimated.
Using Sheer and Randall's estimated delta outflow with
double carriage water, Williams also estimated annual salinity in
the bay. The results suggest that after a climatic warming, a 1-
4-27
-------
California
m sea level rise, and failure of the levees, water of a given
average annual salinity could migrate inland between 4 km (2.5
miles) (GFDL scenario) and 9.6 km (6 miles) (OSU scenario)
(Figure 4-8).
Williams also calculated the average monthly salinity for
Suisun Bay for the three climate scenarios, levee failure, and
double carriage water requirements. Monthly salinities are
higher for all months compared to the base case, except for
winter and early spring months in the GFDL scenario. The greatly
increased runoff of the GFDL scenario (Figure 4-7) during these
months kept the salinity at the same level as the base case.
Williams also modeled how the frequency of a given salinity value
in any month would change. For example, in June salinities that
were exceeded in 50% of the years in the base case might be
exceeded in 80% of the years in both the GFDL and OSU scenarios,
because of the lower outflows predicted under these scenarios.
Implications
Rising sea level could place the delta islands under
increased risk of inundation, not only because of higher water
levels but also because the larger area and volume of the San
Francisco Bay estuary could result in greater wave energy and
higher erosion rates of the levees. Improving the levees just to
protect them against flooding at the current sea level could cost
at least $4 billion (California Department of Water Resources,
1982). With higher sea levels, the cost of maintaining the
levees could increase.
The large water body created if all the levees fail will
have a longer water residence time. This means that any
contamination (salt or other pollutant) will be more difficult to
flush out of the delta region. Also, if saline water fills the
islands when levees fail, significant amounts of freshwater will
be needed to flush out the salt.
Increasing salinity could necessitate increases in carriage
water to maintain freshwater at the export point in the delta or
could require developing a different method to convey freshwater
from reservoirs to users. The increase in carriage water coupled
with the decrease in reservoir storage would most likely mean
reduction in water deliveries to at least some of the system's
users during extended droughts. With higher future water
demands, shortages caused by the higher carriage water-
requirements may not be limited to extended droughts.
4-28
-------
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California
Wetlands in the San Francisco Bay Estuary
Climatic warming could alter two important physical factors
that affect wetland distribution: sea level and freshwater
inflow. Major impacts of sea level rise could include erosion
and marsh inundation. Changes in freshwater inflow can change
the distribution and productivity of estuarine plants and
animals. Josselyn and Callaway (Volume x) estimated the possible
effects of climatic warming on deep-water and wetland habitats of
the San Francisco Bay estuary (see Figure 4-2).
Study Design
Josselyn and Callaway examined the impacts of a 1-, 2-, and
3-m (40-, 80-, and 120-inch) sea level rise by the year 2100. Of
the three scenarios, a 1-m rise by the year 2100 is regarded as
the most realistic. Models were used to project nearly linear
changes in the rate of sea level rise from 1990 through 2100
under these three scenarios. The relationship between
sedimentation rates required for marsh maintenance and sea level
rise rates was examined. The effects of salinity changes on the
distributions and abundances of organisms were' related to various
freshwater inflow scenarios developed by Sheer and Randall (see
Figure 4-7). In the absence of appropriate quantitative models,
biotic changes in the estuary in response to changing salinity
were qualitatively determined based on literature review and
expert judgment.
Limitations
Circulation and sedimentation in the estuary will change
dramatically as sea level rises and if levees fail. The specific
characteristics of these biologically important changes are
unknown at present and were not considered in this study. The
sea level rise scenarios did not consider the possibilities of
sudden changes in sea level. Increased water temperature, which
may directly affect the reproduction, growth, and survival of
estuarine organisms, or may have an indirect effect through
changes in oxygen availability, also was not considered.
Although specific impacts on plants and animals in the estuary
are difficult to assess, the general impacts would most likely be
similar to those reported here.
Results
Rates of sea level rise from 1990 to 2040 for the three scenarios
are presented in Figure 4-9. Once the rate of sea level rise
exceeds the rate of sediment accretion, tidal marsh habitats
4-30
-------
Chapter 4
would become inundated and erosion of the marsh edge could
increase. For the 1-m rise scenario, the rate of rise is not
projected to exceed maximum accretion rates until about the year
2040, while the 2- and 3-m (80- and 120-inch) rise scenarios
suggest rise rates in excess of accretion rates after 2010 and
2000, respectively.
Peak primary productivity, at present, occurs in early
spring in San Pablo Bay and in the summer in Suisun Bay. These
maximum productivity levels could be substantially reduced,
particularly for brackish and freshwater plant species, under the
higher salinities of the OSU scenario (see Figure 4-8), and peak
spring production might shift upstream into the delta if levees
fail. However, under GFDL and GISS conditions, the locations of
maximum production levels might remain in their present positions
if the levees are maintained. If the levees fail, primary
production could increase in the extensive shallow water and
mudflat areas created.
Since many areas currently protected by levees are 1 to 2 m
(40 to 80 inches.) or-more below sea level, levee failure would
cause them to become deepwater areas rather than marshes.
Eventually, some of these formerly leveed areas might receive
enough sediment deposition to support marsh development.
Inundation of marshes and salinity impacts on freshwater and
brackish-water plant species could reduce food and cover sources
for waterfowl (see Figure 4-9). Loss of emergent vegetation
could significantly reduce the numbers of migratory waterfowl
using the managed wetlands along Suisun Bay's north shore.
If levees are maintained under conditions of sea level rise,
salt may build up behind them from the evaporation of standing
water. This salt will cause marsh vegetation to die back and
will reduce the value of these wetlands to wildlife.
Freshwater inflows projected during springtime under the
climatic change scenarios (see Figure 4-7) may be too low to
support anadromous fish (saltwater fish that enter freshwater
areas for spawning). Lower inflows could result in declines
among these populations in this region (Kjeldson et al., 1981).
If levees fail, a large inland lake with fresh to brackish
water quality could be created in the delta. Striped bass and
shad spawn in essentially freshwater conditions and their
spawning could be reduced under increased salinity, especially if
they did not move upstream to relatively fresh water. Marine
fish species could increase in abundance in the Suisun and San
4-31
-------
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Figure 4-9.
Sea level rates at San Francisco from 1990 to 2040
under 1-, 2-, and 3-m (40-, 80-, 120-inch) sea level
rise scenarios. When the rate of sea level exceeds
maximum recorded rates of sediment accretion, marsh
habitats would most likely be converted to deeoer-
water habitats. p
Source: Josselyn and Callaway, Volume _.
4-32
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Chapter 4
Pablo Bays in response to the higher salinities projected, and
freshwater and anadromous species could decrease.
Implications
The loss of wetlands could result in substantial ecological
and economic losses for the region. For example, the managed
wetlands north of Suisun Bay support a hunting and fishing
industry valued at over $150 million annually (Meyer, 1987).
Tourism, hunting, fishing, rare and endangered species, and
heritage values also could suffer.
California Agriculture
California's agricultural production is highly dependent 6n
irrigation which accounts for approximately 80% of the states net
annual water use. Dudek (volume x) used existing agro-ecological
models to explore potential responses of California agriculture
to climatic change.
Study 'Design
Climatic changes from the GISS and GFDL 2xCO2 scenarios were
linked to an agricultural productivity model adapted from
Doorenbos and Kassam (1979). Growth responses to both climatic
change and climatic change plus C02 direct effects were modeled.
These productivity responses were then introduced into the
California Agriculture and Resources Model (CARM; Howitt and
Mean, 1985) which estimates the economic and market implications
of such, changes. Mean surface water supplies under the base,
GISS, and GFDL scenarios were calculated from the simulations of
Sheer and Randall (volume x) and were input to CARM.
Limitations
Further, the CO2 direct effects results should be viewed as
preliminary since they are based on data from growth chamber
experiments that may poorly represent field conditions. This
study did not consider changes in agricultural technology, crop
varieties, planting dates, or changes in water costs. Also, new
crop/location combinations were not considered. The interaction
between climatic change and C02 direct effects on productivity
were not examined but may significantly limit potential growth
increases. No national or international context of agricultural
price signals were considered. These could be a major factor in
determining how California farmers respond to climatic change.
Given these limitations, realistic estimates of agricultural
responses to climatic change may be difficult to obtain. The
4-33
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California
results may be more valuable as indications of potential trends
rather than specific impacts.
Results
Relative to the 1985 base, average yields could be
significantly reduced for California crops in response to
climatic changes alone (i.e., without consideration of direct
effects of C02) . Generally, the greatest impacts are projected
under the hotter GISS scenario. Table 1 presents regional yield
changes for sugarbeets, corn, cotton, and tomatoes. These
projections were generated by the agricultural productivity model
and do not consider economic adustments or water supply
limitations. Tomatoes might suffer the least damage, with
average yields reduced from 5% to 15%. Sugarbeets could be
hardest hit, with average declines from 20% to 40%. Yield
reductions in sugarbeets are projected to be greatest in the
relatively hot interior southern regions. Differences in growth
response between the two climatic scenarios were greatest for
corn and least for tomatoes.
Without economic adjustments, corn yields declined 20% to
41% as projected by the agricultural productivity model under the
GISS scenario (Table 1). With economic adustments, declines of
roughly 21% are projected (Table 1); a result at the lower end of
the direct productivity impacts.
When the direct effects of C02 on crop yields are
considered, yields of sugarbeets, cotton, and tomatoes generally
increased over the 1985 base (Table 1). Corn is unable to
increase growth in response to increases in C02 concentration,
although yield reductions are not as great as with climate change
along (Table 1). Cotton could benefit the most from inadvertant
CO2 fertilization with yield increases ranging from 6% to 41%.
Potential increases in yields in response to C02
fertilization might only be achieved at a cost of increased
groundwater extraction in many areas. For example, when surface
water utilization is projected at 100% of capacity, as in the
Northern San Joaquin region, excess demand would require
increased groundwater usage (Figure 4-10). However, increased
crop yields may offset increased economic costs for water.
Regionally, across all scenarios, (not considering potential
changes outside of California) the largest reductions in crop
acreage are projected in the Imperial Valley while the delta
4-34
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Chapter 4
Table 1. Regional and statewide percentage yield changes (relative to 1985)
under different General Circulation Model climate scenarios.
Regional changes are projected by the Doorenbos and Kassam
agricultural productivity model while statewide production changes
are projected by the California Agriculture and Resources Model
(CARM). The latter estimates include economic adjustment "Net"
includes the direct effects of increases in C02 and climatic
change (CC).
Croo
Regionb
South Coast
Los Angeles
North Interior
Red Bluff
Scenario
GISS
GFDL
GISS
GFDL
sugarbeets
CC Net
-26
-20
-28
-23
21
30
12
21
corn
CC Net
-41
-26
-27
-14
-37
-22
-22
-8
cotton
CC Net
-22
-4
-18
-10
11
41
22
35
tomatoes
CC Net
-7
-5
-15
-13
18
21
11
13
Sacramento Valley
Sacramento
GISS
GFDL
-30
-27
17
22
-20
-6
-14
0
-17
-11
25
34
-12
-8
16
21
Southern San Joaquin
Fresno
GISS
GFDL
-33
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5
-8
-26
-14
-21
-8
-16
-10
25
36
-15
-13
11
14
Southern Deserts
Blythe
CARM Statewide
GISS
GFDL
GISS
GFDL
-40
-39
-30
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15
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-21
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-4
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-19
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6
21
23
35
-13
-12
-13
-11
13
15
5
16
xrefer to Figure 1 for city locations.
Source: Dudek, Volume .
4-35
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Regional crop acreage, groundwater use, and surface water use
changes under different General Circulation Model climate
scenarios. Net effect includes the direct effects of
increases in C02 and climatic change.
Source: Dudek, Volume .
4-36
-------
Chapter 4
region shows the largest gains in acreage (Figure 4-10). This
expansion of agriculture in the delta region would depend on
maintenance of levees protecting farmland. Without considering
C02 fertilization, statewide crop acreage was reduced about 7%
from the 1985 base. When C02 direct effects are considered,
statewide crop acreage approximately equals 1985 base levels.
Implications
Regional changes in cropping locations and patterns of water
use imply potential exacerbation of existing nonpoint source
pollution and accelerated rates of groundwater overdraft with
ensuing environmental impacts.
Changing water supply demands may result in increased
conflicts between water users. In addition, shifts in the
location of agricultural production could play a substantial role
in the future viability of natural systems. Such shifts could
also have a significant impact on the economic viability of small
agricultural communities.
National Agriculture
Adams, et al. conducted a national agricultural study that
includes results relevant to California (Adams et al., volume x) .
The results of the Adams et al. study are not directly comparable
with the results from Dudeks1 study (discussed above) since Adams
et al. considered national agricultural impacts and aggregated
California into a Pacific region with Oregon and Washington.
Further, the two studies did not examine the same set of.crops
and modeled productivity differently (see the Agriculture chapter
of this report for a description of the study's design and
methodology).
Results
Nationally, Adams et al. (volume x) project 2% to 4%
declines in crop acreage in response to climatic change but shows
a 18% to 20% increase in acreage in the Pacific coast states.
This increase in the Pacific region is attributable to the
regions extensive use of irrigated agriculture. In contrast,
most other regions of the U.S. predominantly use dryland farming
and crop acreage might decline in response to moisture stress.
The Adams et al. approach is based on maximizing farmers profits
and indicates that higher yields associated with direct C02
effects might result in further declines-in crop acreage (or, in
the case of the Pacific coast states, less of an increase) since
less acres might be required to produce the necessary crops.
4-37
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California
Water Quality of Subalpine Lakes
Subalpine lakes are common in the California mountains, and
many of these are the source of streams and rivers flowing down
into the lowlands. Changes in the water quality of these lakes
could significantly alter their species composition and nutrient
dynamics and also could have an impact on downstream water
quality and ecosystems. The sensitivity of California's
subalpine lakes to weather variability and climate change has not
been extensively studied. Consequently, Byron et al. studied how
climate controls the water quality of Castle Lake, a subalpine
lake in northern California.
Study Design
Goldman et al. (1989) correlated an index of water quality,
primary production (i.e., the amount of biomass produced by algae
in the lake), with climate variation at Castle Lake.
Consequently, Byron et al. (Volume x) were able to develop
empirical models relating primary production with various climate
parameters.
Limitations
The model is limited to estimating annual values of primary
production; seasonal variability is not calculated. The model
also does not project changes in species composition and nutrient
dynamics, which could have important consequences for water
quality. Changes in upland vegetation and nutrient cycling,
which could also affect the lake's water quality., were not part
of the model.
The estimates of annual primary production produced by this
model are relatively precise, although the results are general in
the sense that no species-specific projections are made.
Results
The model projects that mean annual primary production could
increase under all three of the double C02 scenarios, with
increases ranging from 16% (OSU scenario) to 87% (GISS scenario)
(Figure 4-11). The OSU results are within one standard error of
present productivity, and thus do not represent a significant
decrease in water quality. The transient scenario produced
generally increasing but variable primary production estimates,
with the mean production of the last decade in the transient
scenario about 25% higher than the base (control) case.
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PI
I
u
o>
3
o
o
800
700 -
600 -
500 -
400 -
300 -
200 -
100 -
Meosured
uodel
GFOL
GISS
OSU
V~7\
Figure 4-11. Annual primary production estimates for Castle Lake
showing actual and model values for present
conditions and model values for three General
Circulation Model climate scenarios (see Figure 4
for location of Castle Lake). The solid bars show
one standard error for each estimate.
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California
The increase in annual primary production is attributed
principally to the temperature increase projected by the
scenarios. The higher temperatures resulted in less snow
accumulation, which is correlated with an earlier melting of the
lake ice, and a longer growing season.
Implications
Higher primary production could result in climatic effects
being indirectly felt at higher points in the food web in the
lake and could affect the lake's nutrient dynamics.
Extrapolating these results to other subalpine lakes
suggests their water quality could decrease and their species
composition might change after climatic warming. Increased
primary production can provide additional food for other aquatic
organisms', such as fish, but can also degrade water quality by
ultimately causing a decrease in dissolved oxygen and blocking
light from filtering to lower levels. Fisheries in unproductive
lakes may be enhanced, while trout populations may suffer in
lakes where temperatures rise past a threshold value and oxygen
decreases because of the higher production.
Changes in production and concomitant changes in nutrient
dynamics could affect downstream river and reservoir water
quality. However, since the streams draining subalpine lakes are
well oxygenated, the increased biomass would most likely be
rapidly decomposed and probably would not affect the water
quality of the lower reaches of streams and rivers.
Summary of Effects on Water Resources
In terms of economic and social importance, changes in water
resources are among the most important possible effects of
climatic change in California. A wide variety of factors related
to climatic change could affect water resources, ranging from
factors changing water supply to those affecting water demand.
All the individual projects discussed above addressed some aspect
of climatic impacts on water resources in the State. However,
these studies did not consider all the major factors that will
affect California water resources in the next century, mainly
because of the complexity and inherent difficulties in
forecasting future demand for water. This section discusses
other factors that will affect future water demands that were not
directly considered by the individual studies, including future
changes in agriculture, population, water efficiencies, and
sources of water, including groundwater.
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Chapter 4
Dudek's study used estimates of water deliveries from Sheer
and Randall's study, but changes in agriculture that he
determined, and hence changes in agricultural demand for water,
are not factored back into the water simulation model. For
instance, Dudek's results indicate that because of climatic
conditions, crop acreage in the Imperial Valley decreases,
freeing water used there for irrigation to be used elsewhere in
the State. Also, as cropping patterns change, so would the
pattern of needed water transfers via the water resource system,
thus affecting water deliveries. Finally, Dudek found that
groundwater usage could increase after climatic change when the
direct effects of CO2 are included in his model. Estimated
groundwater usage increases when full use of surficial water
sources does not meet agricultural demands estimated in the
model. Thus, Dudek's results suggest that agricultural demand
for water could exceed surficial supplies after climatic warming,
further exacerbating water shortages.
Not considered in the overall California study, but critical
to determining the magnitude of potential water shortages in the
next century, are population growth and accompanying changes in
water demands. Projections of population growth place the
State's population at about 35 million in 2010 compared with 24
million in 1980, an increase of 45% (California Department of
Water Resources, 1983). An increase of this magnitude will
significantly intensify municipal water demands, exacerbating
shortfalls. Meeting the needs of the growing population in face
of competing demands from agriculture raises some important
policy questions that are discussed in the policy section.
If water shortages become more common, it is reasonable to
assume that agricultural, industrial, and residential users will
change water-use efficiency. Changes in efficiency were not
considered in any of these projects but could moderate possible
future shortages. Any change in water pricing or water law also
could affect water demand and supply, but these factors are
probably impossible to project very far into the future.
Groundwater usage is discussed in Dudek, but the overall
impacts of climatic change on groundwater are not addressed in
this project. As demand for water increases beyond the
capability of the water resource system to deliver the needed
water, mining of groundwater (as Dudek shows for agriculture) is
one option users could adopt to meet their demand. Using
groundwater could lessen the severity of water shortages in the
short term but presents environmental problems, such as land
subsidence, over the long term.
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In general, given the current water resource system, the
projected response of that system to climatic change and
qualitative considerations of future changes in water demand
suggest that water shortages could be significantly greater than
estimated here.
Vegetation of the Sierra Nevada
To better understand the sensitivity of natural vegetation
in California, Davis studied how the terrestrial vegetation
growing in the California Sierra Nevada has changed over the past
12,000 years. The climatic changes that occurred during this
period suggest how the vegetation that currently exists in the
mountains could respond to future climatic changes. In
particular, the middle latitudes of the Northern Hemisphere are
believed to have been warmest (1-3°C warmer than today) about
6,000 years ago (Budyko, 1982), and parts of western North
America were apparently warmest 9,000 years ago (Ritchie et al.,
1983; Davis et al., 1986). Thus, the period that existed between
6,000 and 9,000 years ago in California could present a possible
analogue to a warmer future climate.
Study Design
The composition of the vegetation that has existed in the
central Sierra Nevada over the last 12,000 years was determined
using fossil pollen analysis. Fossil pollen samples were
collected from five lakes situated along an east-west transect
(see Figure 4-4) passing through the major vegetation zones of
the Sierra Nevada. Dissimilarity values were calculated between
modern and fossil pollen samples to determine the past vegetation
at a particular site.
Limitations
The climate projected in the three double CO2 scenarios is
different from the climate that probably existed between 6,000
and 9,000 years ago in the Sierra Nevada, according to Davis.
The vegetation that persisted then suggests that the climate was
drier and a little cooler than it is today. This is a marked
contrast to the warmer and slightly wetter climate scenarios used
in this report. Consequently, the results from this study do not
provide a past analogue for the climate scenarios, but
nonetheless present a possible analogue for how Sierra Nevada
vegetation could respond to a warmer Northern Hemisphere climate.
A relatively small set of modern pollen samples was
available for comparison to the fossil samples; therefore, the
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Chapter 4
precision of the vegetation reconstruction is somewhat uncertain.
Also, the precision of the estimated elevational shifts in the
vegetation zones is low because of the limited number of fossil
sites available for the analysis. Nevertheless, this study
provides a good general summary of the vegetation changes in the
Sierra Nevada during the past 12,000 years.
Results
The forests existing in the western Sierra Nevada 9,000
years ago resembled those found east of the crest today (Figure
4-12), with lower forest cover and tree density. Pine and fir
densities, in particular, were lower. Between 9,000 and 6,000
years ago, the vegetation gradually became similar to the modern
vegetation in the same area, and by 6,000 years ago the modern
vegetation zones were established on both sides of the Sierra
crest. The vegetation at 6,000 years ago is subtly different
from that in the area today, with less fir and more sage. The
forests may have been slightly more open than today.
Implications
If climatic conditions of the Sierra Nevada in the next
century are similar to those that existed 9,000 years ago, major
changes could occur in the forests of the region, both in
composition and density. The vegetation changes could generate
significant environmental impacts, ranging from changes in
evapotranspiration and related feedbacks to local hydrology, to
changes in nutrient cycling and soils, which could degrade the
water quality of mountain streams. Fire frequencies could
increase as a function of changes in fuel loads, ignition
frequencies, and vegetation. If dead wood rapidly builds up
because of the decline in one or more tree species, large
catastrophic fires could occur.
If future forests west of the Sierra crest become more
similar to current forests east of the crest, timber production
could significantly decline. Based on National Forest Inventory
data, timberlands east of the crest currently support only about
60% of the wood volume of timberlands west of the crest (U.S.
Forest Service, Portland, Oregon, personal communication). The
different climate could also necessitate a change in timber
practices (e.g., reforestation techniques).
Vegetation change in response to climatic change could
produce additional stress for endangered animal species as their
preferred habitats change. Populations of nonendangered wildlife
also could be affected as vegetation changed, with some species
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4000
3000
2000
1000
0
(West)
MODERN
Tioga Pass Pond
Starkweather q_
Exchequer q,
Balsam
a Barrett
(East)
4000
3000
2000
1000
0
a Barrett
Tioga Pass Pond
Starkweather
Exchequera
Baisam
(West)
(East)
4000 -i
3000
2000 -
1000
0 J
Elev- (m)
9K
Tioga Pass Pond
Starkweather p.
Exchequer a
Baisam
a Barrett
(West)
(East)
Figure 4-12. Vegetation zonation in the central Sierra Nevada at
present; 6000 years (6K) before present; and 9000
years (9K) before present. (See Figure 4-4 for
approximate location of fossil pollen sites.) The
dashed lines indicate uncertainty in the placement
of the vegetation zone boundaries.
SA = Subalpine
UM = Upper Montane
ES = Eastern Sub-alpine
PF = Pine Forest
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Chapter 4
increasing in abundance and others decreasing. Some plant
species, especially alpine species, also could become endangered.
Warmer temperatures could favor subalpine species over alpine
species at some of the higher elevation peaks and ridges in the
Sierra Nevada, leading to local extinction of the alpine species.
Electricity Demand
The electric power industry is highly sensitive to
uncertainty in future energy demands associated with potential
climate change. As part of a national study, Linder and Inglis
estimated northern California's energy demand for the years 2010
and 2055. (See the Energy Demand chapter of this report for a
description of the study's design and methodology.)
Results
In California, climatic change scenarios result in only
small changes in electrical utility generation and costs by the
year 2010. Annual power generation is estimated to increase by 1
to 2%, and new generation capacity requirements would be less
than 1% greater than increases without climate change. By the
year 2055, annual power generation is estimated to increase by 3
to 5%, and new generation capacity requirements would be 14 to
20% greater than non-climate induced needs. Then, cumulative
investments in new capacity would cost $10 to $27 billion.
Implications
More powerplants may need to be built; these will need more
cooling water, further depleting the water supply. Climate-
induced changes in hydrology may reduce hydropower generation and
increase dependence on fossil fuels and nuclear power. Increased
use of fossil fuels may provide positive feedback for the
greenhouse effect and may deteriorate local air quality.
Air Pollution
Morris et al. (Volume x) studied possible interactions of
climatic change and air pollution in California. (The study's
design and methodology are discussed in the Air Quality chapter
of this report.)
Results
Morris et al. (Volume x) project an increase in ozone
concentration of up to 20% during some days in August in response
to a 4°C (7°F) climatic warming in central California. The
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California
National Ambient Air Quality Standard (NAAQS) for ozone is 12
ppm. The modeling of Morris et al. estimates a 30% increase in
August days that exceed this standard. Furthermore, the area
exceeding the NAAQS could increase by 1,900 km2 (730 mi2), and
the number of people exposed to these elevated ozone levels could
increase by over 450,000.
Implications
The greenhouse effect climatic changes may significantly
change the air's chemistry on urban and regional scales. These
changes may exacerbate existing air quality problems around
California metropolitan areas and agricultural areas of the
Central Valley.
POLICY IMPLICATIONS
An overall question that applies to resource management in
general is, "What is the most efficient way to manage natural
resources?" Currently, management is based on governmental
jurisdiction with, for example, forests managed at the local,
State, or Federal level. Management of hydrologic systems is
also based on governmental jurisdiction. An alternative would be
to manage these systems using natural boundaries as the criteria
for determining management jurisdiction. The pros and cons of
such a management strategy deserve at least some preliminary
research.
Water Supply and Flood Control .
Water supply is the basis for most economic development in
California. Yet, almost all the water available in the SWP is
allocated for use. A major problem is to accommodate rising
demand for water, interannual climate fluctuations, and the need
to export water from northern California to southern California.
In addition, the results from these studies suggest that
climate change over the next 100 years could cause earlier
runoff, thus reducing water deliveries below their projected 1990
level. This situation would create a set of major policy
problems for the water managers and land use planners in
California.
Two major policy questions can be raised concerning the
possible reduction in water deliveries: How can the water
resource system be changed to prevent a decrease in water
deliveries caused by climate change? If water deliveries fall
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Chapter 4
short of demand, how should potential water shortages be
allocated?
Approaches for Modifying the Water Resource System
Several possible approaches can be attempted to increase
water deliveries. First, management of the system could be
modified. For instance, the most recent SWP development plan
suggests the possibility of State management of both SWP and CVP
facilities (California Department of Water Resources, 1987a).
Complete joint management could produce more than 1 million acre
feet (maf) additional reliable yield in the system. Steps toward
greater cooperation have been taken. The Coordinated Operating
Agreement (H.R. 3113) between the SWP and the CVP, ratified in
1986, allows the SWP to purchase water from the CVP. Using
conservation techniques and improving the efficiency of transfer
might also increase water deliveries.
Operating rules for the reservoirs also could be modified to
increase allowable reservoir storage in April, which would
increase water storage at the end of the rainy season and
deliverable water during the peak demand season in midsummer.
However, an increase in water storage in the late winter and
early spring is likely to reduce the amount of flood protection
(increase the risk of flooding) in the region; this in itself
could negatively affect owners of floodplain property. Floods
also place the delta islands at risk because of higher water
levels. The tradeoff between water supply and flood control in
northern California represents a potentially serious policy
conflict affecting all levels of government in the region. In
fact, a meeting between representatives of the State DWR and
Bureau of Reclamation, which was held to discuss Sheer and
Randall's (Volume x) results, concluded that any likely changes
in reservoir operation that would avoid a significant loss of
flood safety would most likely bring about little improvement in
the system's performance under the given climatic scenarios.
Detailed study of this point is needed, however.
The second approach to maintain or increase water deliveries
might be to construct new water management and storage
facilities. However, trends over the past decade have shifted
away from planning large storage facilities (e.g., the Auburn Dam
and Delta Peripheral Canal). Building new facilities is
expensive and raises serious environmental concerns such as
development of wild and scenic rivers. Another option is to use
smaller facilities, such as the proposed new off-stream storage
facility south of the delta, and to improve the delta's pumping
and conveyance facilities. With the help of these facilities,
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California
the SWP plans to achieve a 90% firm yield (the amount that can be
delivered in 9 out of 10 years) of about 3.3 maf by 2010
(California Department of Water Resources, 1987a). Another
relatively inexpensive option for off-line storage is artificial
recharge of groundwater during wet years. The SWP is currently
pursuing a proposal to deliver surplus water to groundwater
recharge areas in the southern Central Valley to provide stored
water for dry years.
The third approach to increase water deliveries is to turn
to other sources of water. For instance, use of groundwater
could be increased. However, in many metropolitan areas,
groundwater bodies are currently being pumped at their
sustainable yields. Any increase in pumping could result in
overdraft. Furthermore, decisions to use groundwater' are made by
local agencies and/or individual property owners, and groundwater
is not managed as part of an integrated regional water system.
Whether to include it in the system is an important policy issue.
Another option is for southern California to choose to fully
use its allotment of Colorado River water (which could lead to
conflicts between California and other users of that water,
especially Arizona). Other possibilities include desalinization
plants, cloud seeding over the Sierras, and reuse of wastewater.
However, desalinization plants are energy intensive and may
exacerbate air quality problems. Also, cloud seeding is
controversial, since downwind users may not be willing to lose
some of their precipitation.
Options for Allocating Water Shortages
The second major policy question is how to best allocate
potential water shortages. One way would be to allow greater
flexibility in water marketing. The adverse effects of this
policy change (e.g., perhaps water becoming too expensive for
agriculture and possible speculative price increases) could be
ameliorated through a variety of governmental policies. Yet,
even with regulation, any changes in the current system along
these lines would most likely be very controversial.
A second way to allocate the shortages is to rely on those
mechanisms used in the past to deal with droughts and water
shortages, specifically governmental restrictions on water use.
In the past, these have included restrictions on "nonessential"
uses of water (e.g., watering of lawns), increased use
efficiency, and transfers of agricultural water to municipal and
industrial uses. Increased efficiency of water usage through
various conservation techniques could effectively increase the
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Chapter 4
number of water users without actually increasing the amount of
water delivered. If climate gradually changes and water
shortages become more common, these restrictions could become
essentially permanent.
Sacramento and San Joaquin River Delta
The delta area of the Sacramento and San Joaquin Rivers in
the San Francisco Bay estuary receives great attention from
governmental bodies at all levels because of its valuable
agricultural land, its crucial role in the State's water resource
system, and its sensitive environment. The results of the
studies in this overall project suggest that this region
could be significantly affected by climatic change. Major
changes could occur in delta island land use and in the water
quality of the San Francisco Bay estuary. The policy
implications of these possible changes are discussed below.
Delta Island Land Use
A critical land use issue is whether to maintain the levees
surrounding islands threatened by inundation. Much of the land
present on these islands is below sea level and is usable for
agriculture, recreation, and settlement only through levee
protection.
The individual delta islands have a significant range of
values. For example, some islands contain communities and
highways, and others are strictly agricultural. The property
value of the islands is about $2 billion (California Department
of Water Resources, 1987b). The islands also help repel saline
water from the delta pumping plants (see Figure 4-2).
The levees have been failing at an increasing rate in recent
years, and further sea level rise could increase failure
probability. Improving the levees to protect the islands from
flooding at the existing sea level and flood probability would
cost approximately $4 billion (California Department of Water
Resources, 1982).
The issue of levee failure raises three important policy
questions. First, will some or all of the levees be maintained?
The range of options concerning the levees includes inaction,
maintenance of the status quo, strategic inundation of particular
islands, and construction of polder levees.
Inaction, meaning the levees are not improved with time,
could eventually lead to the formation of a large brackish-water
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California
bay as all of the levees failed. Williams (Volume x) suggests
that the area of the San Francisco Bay estuary could triple if
all the levees failed.
Currently, the general policy is to maintain the delta's
configuration. One important policy favoring the maintenance of
the levees is the Delta Levee Maintenance Subventions Program, in
which State financial assistance is available for maintaining and
improving levees. The value of the islands for agriculture and
maintenance of water quality (see below) has created additional
institutional support for maintaining the levees, even though the
cumulative cost may exceed the value of the land protected.
Future funding decisions for this and related programs should
consider the possibility of climate change. If the levees are
maintained, an important policy question is who will pay for the
maintenance.
Not all the islands are of equal value, especially with
regard to their value in protecting the freshwater delivery
system. A possible future policy response to rising sea level
would be to maintain only certain levees and not reclaim other
islands as they become flooded. In essence, this would be a
strategic inundation policy. Some precedence exists for this
policy, as Mildred Island was flooded in 1983 and not reclaimed;
the high cost of reclaiming the island relative to its value was
cited as a rationale.
Construction of large levees similar to the polders in
Holland is an option for protecting the islands and maintaining
shipping channels. However, this approach would be expensive
and, though it has been discussed, has not attracted 'much serious
attention.
Another policy question concerns failure of the levees. If
all or some levees are allowed to fail, will landowners be
compensated? If so, where will the money come from? The delta
islands contain some of the most valuable agricultural land in
the State. Loss of this land would be a severe economic hardship
for the local farmers and for the associated business community.
Whether these farmers should be compensated for their loss is an
important public policy issue.
A final policy question concerns management of the delta
islands. How will management of the delta islands be
coordinated? Currently, four government bodies have jurisdiction
over the islands at the local, State, and Federal levels.
Coordination of these bodies will be required to reach decisions
regarding the future of individual delta islands.
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Chapter 4
Water Quality of San Francisco Bay Estuary
The intrusion of saline waters into the upper reaches of the
San Francisco Bay estuary could be a major problem in a warmer
climate. Climate change is projected to cause increases in
salinity in the estuary, largely as a result of sea level rise,
levee failure, and the inadequacy of freshwater inflow to offset
the increase in salinity. Furthermore, land subsidence due to
groundwater extraction could augment sea level rise. In some
areas of the estuary, subsidence up to 1.5 m (59 inches) has
occurred within the recent past (Atwater et al., 1977) .
Maintenance of current levels of salinity is addressed in
the Water Rights Decision 1485 (D-1485) of 1978. This decision
requires that water quality standards in the delta be maintained.
If they are not, additional water must be released from
reservoirs to improve the delta water quality, which could reduce
the amount of water available for delivery. Current policy does
not explicitly take into account the potential for future climate
change. Thus, D-1485 could be interpreted as requiring
maintenance of delta water quality standards even if sea level
rises, causing further penetration of saline water into the
Delta. Delta water quality standards are currently being
reviewed at the Bay-Delta Hearing in Sacramento. This hearing
began in mid-1987 and is expected to continue for 3 years. The
choice of future options will be greatly affected by decisions
made at the hearing.
Possible methods of combating the impacts of saltwater
intrusion include maintaining levees, increasing freshwater
outflows, reducing withdrawals, enlarging channels, constructing
a barrier in the Carquinez Strait or lower delta, and/or
constructing a canal around the delta's periphery.
Alternatively, the freshwater pumping plants could be moved to
less vulnerable sites. Decisions regarding response options will
not be easily made. Levee maintenance and construction are
costly. The water delivery agencies might be reluctant to
increase delta outflows or reduce withdrawals. Enlargement of
delta channels, construction of saltwater barriers, and
construction of a peripheral canal are extremely controversial
environmental issues. Another possible response to these
climatic impacts would be a gradual, planned retreat from the
delta, devoting resources to options compatible with the absence
of a freshwater delta. This option would also be very
controversial, both politically and environmentally.
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Water Quality of Freshwater Systems
Water quality of lakes, streams, and rivers could change as
climate changes. Results from the Castle Lake study indicate
that primary production of subalpine lakes could increase, with
the potential for changes in the water quality of mountain
streams (Byron et al., Volume x). Reduction in summer flows of
streams and rivers in the Central Valley Basin could concentrate
pollutants in these aquatic systems. The major policy question
relating to these potential changes is, "How will potential
reductions in water quality below levels mandated in the current
Water Quality Act of 1987 (Public Law 100-4) be prevented?"
Maintaining water quality despite decreased summer flows
could be difficult and expensive. Controlling nonpoint source
pollution is a goal of the Water Quality Act of 1987, and meeting
this goal in the future could be more difficult and expensive
because of the lower summer flows. Changes in land use near
water courses to prevent runoff from agricultural land from
reaching the water courses may be required. Reducing herbicide
and pesticide use could also be another response, but this could
harm agricultural.production. Another option for preventing an
increase in concentrations of pollutants in river reaches below
reservoirs is to increase releases of reservoirs during summer
months, which would dilute the pollutants. However, this
strategy would have obvious negative impacts on water deliveries.
Municipalities located along rivers in the Central Valley
Basin and that release treated sewage into them also could face
increased difficulties in meeting water quality standards.
Options include expanding sewage treatment facilities, which is
expensive; releasing water from reservoirs to dilute the
pollutants, as discussed above; or controlling the production of
wastewater. Any municipalities planning for new sewage treatment
plants should include climatic change as one factor in the design
criteria.
Reductions in summer flows could harm populations of aquatic
organisms and terrestrial organisms that use riparian habitats.
To the extent that these species become threatened with
extinction, laws requiring preservation of endangered species
(e.g., Endangered Species Act of 1973) may be invoked as a legal
basis for increasing reservoir releases to preserve these
species. This could place into conflict the governmental
agencies and public constituencies concerned with preservation of
biodiversity and those concerned with economic impacts on
agriculture and industry.
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Chapter 4
Terrestrial Vegetation and Wildlife
Changing species composition and productivity might alter
the character of forestry operations and the aesthetic appeal of
currently popular recreational areas. Climate-induced reductions
in growth and regeneration rates, and increases in losses from
wildfire and insect damage and mortality, could decrease the size
and value of industrial forests in the State. How these changes
will be managed is a complex question involving all levels of
government as well as private landowners.
One major step in response to possible future climatic
change is to incorporate climate considerations into current
planning processes. The Forestry chapter of this report
discusses Federal planning for effects of climate change on
forests. Similar planning changes could be made at other levels
of government. Coordinating the actions of government agencies
involved with land management to climatic change in California is
another possible response.
The flora and fauna in California are highly diverse and
include many rare and endangered species. Climate could change
faster than some species could adapt, leading to local extinction
of these species. Species conservation (as mandated by the Rare
and Endangered Species Act of 1973) might require habitat
reconstruction and/or transplanting in some situations.
Monitoring programs may need to be instituted to track trends in
populations and communities. Extensive programs have been
developed for currently endangered species in the State (e.g.,
the California condor), and similar efforts- would probably be
mounted in the future for other highly valued species.
Agriculture
Changes in water availability and temperature stresses are
projected to affect agricultural production. How will changes in
agricultural production and crop types be managed, and how will
California agriculture respond in national and international
settings? (See the Agriculture chapter of this report for
further discussion.)
Historically, agriculture has quickly adapted to climatic
fluctuations. New technology and reallocation of resources might
offset the impact of changed climatic conditions and water
availability. Improved farm irrigation efficiency, such as
extensive use of drip irrigation, could mitigate the impact of
water delivery shortages. Water marketing may provide a cost-
effective means of meeting water demands and providing market
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California
opportunities for conserving water (Howitt et al., 1980). For
example, water marketing may provide rights holders with the
financial ability to invest in water conservation programs to
cope with the impacts of climatic warming on water availability.
Changes in cropping locations and patterns of water use
could exacerbate nonpoint source pollution and accelerated rates
of groundwater overdraft. Further, changing water supply demands
may heighten the conflicts between water allocation strategies
and ecosystem and wildlife values.
It is uncertain how agricultural effects would be manifest
in California's evolving economic and policy environment. For
example, increased commodity prices could mitigate financial
impacts of potential reductions in crop acreage and production.
Wetland Vegetation and Fisheries
Wetland species are valuable ecologically, aesthetically,
and economically (photography, hunting, fishing, etc.). With
rising sea level, areas supporting shallow water vegetation might
be inundated and converted to deep-water habitats supporting
different species. New shallow-water sites could be created by
artificially adding sediment. This option features its own
environmental impacts and would most likely be expensive.
However, maintaining shallow-water vegetation is important not
only to the conservation of plant species but also to migratory
birds, which feed on such vegetation.
Salinity impacts on phytoplankton and fisheries might be
controlled via levee maintenance coupled with increases in delta
outflow.
Shoreline Impacts of Sea Level Rise
The California coast includes a diverse array of shorelines
ranging from cliffs to sandy beaches. Erosion along these
coastlines may increase as a consequence of sea level rise. Such
erosion could substantially damage shoreline structures and
recreational values, and preventing the erosion would be very
costly. For example, protecting the sewer culvert of the San
Francisco Westside Transport Project from potential damage caused
by sea level rise may cost over $70 million (Wilcoxen, 1986).
Sound planning for shoreline structures should consider
future erosion that may be caused by sea level rise. (See Sea
Level Rise chapter 'for further discussion of these issues.)
4-54
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Chapter 4
The accumulation of sediment behind water project dams and
the effects of diversion structures, dredging operations, and
harbor developments have limited the source of sediment for beach
maintenance (particularly along the southern California coast).
Individual landowners and institutions constructing such
structures should consider their effects on sedimentation
processes. Only through artificial deposition of sand (primarily
from offshore sources) have southern Californian beaches been
maintained. Beaches provide recreational areas and storm
buffers, and their maintenance will require a major and continued
commitment.
Air Quality
Increasing temperatures could exacerbate air pollution
problems in California, causing an increase in number of days in
which pollutant levels are higher than National Ambient Air
Quality Standards. Devising technological and regulatory
approaches to meet ambient air standards is currently a major
challenge in certain regions of the state and these efforts must
be continued. In the future, meeting air quality standards may
become even more difficult to achieve under a warmer climate.
Policy makers such as EPA and the California Air Quality Board
may wish to consider possible climatic changes as they formulate
long-term management options for improving air quality, to ensure
air quality standards are met under warmer conditions.
Energy Demand
A warmer climate could affect both energy demand and supply.
For instance, higher temperatures could cause increased cooling
demands, and changes in runoff could affect hydroelectric power
generation. Consequently, institutions in California that are
involved with energy planning, such as the State Energy Resources
Conservation and Development Commission, should begin to consider
climate change in their planning efforts so that future energy
demands can be met in a timely and efficient fashion.
4-55
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California
REFERENCES
Atwater, B.F., C.W. Hedel, and E.J. Helley. 1977. Late Quaternary
Depositional History, Holocene Sea Level Changes, and Vertical
Crustal Movement, Southern San Francisco Bay. U.S. Geological
Survey Professional Paper 1014. Menlo Park, CA: U.S. Geological
Survey.
Atwater, B.F., S.G. Conard, J.N. Dowden, C.W. Hedel, R.L.
MacDonald, and W. Savage. 1979. History, landforms, and
vegetation of the estuary's tidal marshes. In: Conomos, T.J.,
ed. San Francisco Bay: The Urbanized Estuary. San Francisco, CA:
Pacific Division, American Association for the Advancement of
Science, pp. 347-386.
Barbour, M.G., and J. Major. 1977. .Terrestrial Vegetation of
California. New York: John Wiley and Sons.
Budyko, Mi.I. 1982. The Earth's Climate: Past and Future. New
York: Academic Press.
California Department of Water Resources. 1982. Delta Levees
Investigation. Bulletin 199. Sacramento, CA: California
Department of Water Resources.
California Department of Water Resources. 1983. The California
Water Plan: Projected Use and Available Water Supplies to 2010.
Bulletin 160-83. Sacramento, CA: California Department of Water
Resources.
California Department of Water Resources. 1985. California State
Water Project. Typewritten brief. Sacramento, CA: California
Department of Water Resources.
California Department of Water Resources. 1986. Operations
Criteria Applied in DWR Planning Simulation Model. Memorandum
report. Sacramento, CA: California Department of Water
Resources.
California Department of Water Resources. 1987a. California
Water: Looking to the Future. Bulletin 160-87. Sacramento, CA:
California Department of Water Resources.
California Department of Water Resources. 1987b. Sacramento-San
Joaquin Delta Atlas. Sacramento, CA: California Department of
Water Resources.
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Chapter 4
California Division of Forestry and Fire Protection. 1988.
California's Forest and Rangelands: Growing Conflict Over
Changing Uses. Sacramento, CA: Forest and Rangeland Resources
Assessment and Policy Act Committee.
Conomos, T.J., R.S. Smith, and J.W. Gartner. 1985. Environmental
Setting of San Francisco Bay. Hydrobiologia 129:1-12.
Davis, O.K., J.C. Sheppard, and S. Robertson. 1986. Contrasting
climatic histories for the Snake River Plain result from multiple
thermal maxima. Quaternary Research 26:321-339.
Denton, R.A., and J.R. Hunt. 1986. Currents in San Francisco Bay.
Final report. Berkeley, CA: University of California.
Doorenbos, J., and A.H. Kassam. 1979. Yield Response to Water.
FAO Irrigation and Drainage Paper No. 33. Rome: FAO.
Fernald, M.L. 1950. Gray's Manual of Botany, 8th ed. New York:
American Book Co.
Fischer, H.B. 1970. A Method for Predicting Pollutant Transport
in Tidal Waters. Contribution No. 132. Berkeley, CA: University
of California Water Resources Center.
Gleick, P.H. 1987a. Regional hydrologic consequences of increases
in atmospheric C02 and other trace gases. Climatic Change 10:137-
161.
Gleick, P.H. 1987b. The development and testing of a water
balance model for climate impact assessment: modeling the
Sacramento Basin. Water Resources Research 23:1049-1061.
Goldman, C.R., A. Jassby, and T. Powell. 1989. Interannual
fluctuations in primary production: impact of climate and weather
at two subalpine lakes. Limnology and Oceanography, In press.
Howitt, R.E., D.E. Mann, and H.J. Vaux Jr. 1980. The economics of
water allocation. In: Englebert, E.A., ed. Competition for
California Water. Berkeley, CA: University of California Press.
Howitt, R.E., and P. Mean. 1985. Positive Quadratic Programming
Models. Working Paper No. 85-10. Department of Agricultural
Economics, University of California, Davis.
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California
Kjeldson, M.A., P.P. Raquel, and F.W. Fisher. 1981. Influences of
freshwater flow on chinook salmon in the Sacramento-San Joaguin
Estuary. In: Cross, R.D., and Williams, D.L., eds. Proceedings of
the National Symposium on Freshwater Inflow to Estuaries, Vol. 2.
Washington, DC: U.S. Department of the Interior, pp. 88-108.
Leverenz, J.W., and D.J. Lev. 1987. Effects of carbon dioxide-
induced climate changes on the natural ranges of six major
commercial tree species in the western United States. In:
Shands, W.E., and J.S. Hoffman, eds. The Greenhouse Effect,
Climate Change, and U.S. Forests. Washington, DC: The
Conservation Foundation, pp. 123-155.
Macdonald, K.B. 1977. Coastal salt marsh. In: Barbour, M.G., and
J. Major, eds. Terrestrial Vegetation of California. New York:
John Wiley & Sons, pp. 263-294.
Major, J. 1977. California climate in relation to vegetation. In:
Barbour, M.J., and J. Major, eds. Terrestrial Vegetation of
California. New York: John Wiley & Sons, pp. 11-74.
Meyer, P.A. 1987. The value of wildlife in San Francisco Bay.
Exhibit 38, entered by the Bay Institute of San Francisco to the
State Water Resources Control Board in Sacramento, CA.
Miller, C.S., and R.S. Hyslop. 1983. California: The Geography of
Diversity. Palo Alto, CA: Mayfield.
Munz, P.A., and D.D. Keck. 1959. A California Flora. Berkeley,
CA: University of California Press.
Nichols, D.R., and N.A. Wright. 1971. Preliminary, map of historic
margins of marshland, San Francisco, California. U.S. Geological
Survey Open File Map, San Francisco Bay Region Environment and
Resource Planning Study. Basic Data Contribution 9.
Raven, P.H. 1977. The California flora. In: Barbour, M.G., and
J. Major, eds. Terrestrial Vegetation of California. New York:
John Wiley & Sons, pp. 109-137.
Ritchie, J.C., L.C. Cwynar, and R.W. Spear. 1983 Evidence from
north-west Canada for an early Holocene Milankovitch thermal
maximum. Nature 305:126-128.
Sheer, D.P., and M.L. Baeck. 1987. Documentation of the CVP/SWP
Simulation Models Developed by WRMI. Columbia, MD: Water
Resources Management, Inc.
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Sudman, R.'S. 1987. Layperson's Guide to the Delta. Sacramento,
CA: Western Water Education Foundation.
U.S. Bureau of Reclamation. 1985. Summary Statistics, 1984;
Volume 1: Water, Land and Related Data. Denver, CO: U.S. Bureau
of Reclamation, Division of Water and Land Technical Services.
U.S. Department of Agriculture. 1987. Agricultural Statistics
1987. Washington, DC: U.S. Government Printing Office.
U.S. Department of the Interior. 1986. National Forest Statement
of Receipts, Fiscal Year 1986. Washington, DC: U.S. Government
Printing Office.
U.S. Environmental Protection Agency. In prep. Ecological
Effects of Global Climatic Change. Chapter 5. In: U.S. EPA
Global Climatic Change Program.
U.S. Maritime Administration. 1985. Containerized cargo
statistics, 1983. Washington, DC: Government Printing Office.
Wilcoxen, P.J. 1986. Coastal erosion and sea level rise:
implications for ocean beach and San Francisco's Westside
Transport Project. Coastal Zone Management Journal 14:173-191.
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CHAPTER 5
GREAT LAKES
DRAFT
FINDINGS
Global climate change could affect the Great Lakes by lowering
lake levels, reducing the ice cover, degrading water quality in
rivers and shallow areas of the lakes. It could also expand
agriculture in the north, change forest composition, decrease
regional forest productivity in some areas, increase open water
fish productivity, and alter energy demand and supply.
Lakes
o Average lake levels could fall by one-half to two and one-half
meters because of higher temperatures under the scenarios in
this report. A drop of one meter would leave average levels
below historic lows. Even if rainfall increases, the levels
would fall because increased temperatures reduce the snowpack
and accelerate evaporation. The estimates of lake level drop
are sensitive to assumptions about evaporation; under certain
limited conditions, lake levels could rise.
o As a result of higher temperatures, the duration of ice cover
on the lakes would be reduced by one to three months. Ice
would still form in near-shore and shallow areas. Changes in
wind speed and storm intensity would affect the duration of
ice cover.
o Shoreline communities would have to make adjustments to lower
lake levels over the next century. Hundreds of millions of
dollars would have to be spent along the Illinois shoreline
along, dredging ports, harbors, and channels to greater depths
than without climate change. Water intake and outflow pipes
may have to be relocated. On the other hand, lower levels
would expose more beaches, which would enhance shoreline
protection and recreation.
o Climate change could have both good and bad effects on
shipping. Lower lake levels would necessitate increased
dredging of ports and channels or reduced cargo loads.
Without dredging, shipping costs could rise 2 to 33 percent
due to a reduction in cargo capacity. However, reduced ice
cover would lengthen the shipping season and would
sufficiently compensate for lower lake levels up to a drop of
several meters.
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Great Lakes
Water Quality and Fisheries
o Higher temperatures would change the thermal structure of the
Great Lakes. The result would be a longer and greater
stratification of the lakes and increased growth of algae.
These two factors would combine to reduce dissolved oxygen
levels in shallow areas of lakes such as Lake Erie. A study
of southern Lake Michigan found that annual turnover of the
lakes could be disrupted.
o Climate change could increase concentrations of pollutants
in the Great Lakes Basin. Dredging of ports could suspend
toxic sediments in near-shore areas. Potential reductions
in river flow in the Basin would create higher
concentrations of pollutants in streams. The disposal of
toxic dredge spoils was not studied in this report.
o The effects on fisheries would be miked. Higher temperatures
may expand fish habitats during fall, winter, and spring and
accelerate the growth and productivity of open water fish such
as bass, lake trout, and pike. On the other hand, fish
populations could be hurt by decreased summer habitats, lower
summer dissolved oxygen levels and by potential loss of
wetlands due to dropping lake levels. The effects of loss of
wetlands, reductions in ice cover, introduction of new exotic
species, and increase in species interaction were not
analyzed.
Forests
o The composition and abundance of forests in the Great Lakes
region will change. Higher temperatures and lower soil
moisture could reduce forest biomass in dry sites in central
Michigan by 77 to 99 percent. These mixed hardwood and oak
forests would become oak savannas or grasslands. In northern
areas such as Minnesota, boreal and cedar bog forests could
change to treeless bogs, and mixed northern hardwood and
boreal forestry in upland areas would become all northern
hardwoods. Productivity could decrease on dry sites and
bogland sites, but increase on some well drained wet sites.
Softwood species that are currently commercially important
could be eliminated and replaced by hardwood, such as oak and
maple, which are useful for different purposes.
o Depending on the scenario, declines in forests could be
evident in 30 to 60 years. These results do not reflect
additional stresses, such as acid rain and oxidant levels, nor
5-2
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Chapter 5
do they reflect the possible beneficial impacts of increased
CO2 levels.
Agriculture
o Considering climate change alone, corn and soybean yields in
northern areas, such as Minnesota, could increase by 50 to 100
percent and would decline in the rest of the region by up to
60 percent. The combined effects of climate and C02 could
further increase yields in the North, and would result in net
increases in the rest of the region, unless climate change is
severe.
o Agricultural production in the northern part of the region
could expand as a result of declines elsewhere. Acreage in
the Corn Belt states may change little. However, the presence
of glaciated soils in the North could limit this expansion.
Wider cultivation in the north could increase erosion and
runoff, and degrade surface and groundwater quality. Increased
agriculture would require changes in the infrastructure base,
such as transportation networks.
Electricity Demand
o There would be little net change in annual electricity demand.
In northern areas, such as Michigan, reduced heating needs
would exceed increased cooling requirements, while in southern
areas, such as Illinois, cooling needs would be greater than
heating reductions. The annual demand for electricity in the
entire region could rise by 1 to 2 billion kilowatt hours by
2010 and by 8 to 17 BKWH (less than 1%) by 2055. This study
did not analyze the reduced use of other fuels such as oil and
gas in the winter, changes in demand due to higher prices, and
the impacts on hydroelectric supplies. Previous studies have
suggested that reduced lake levels and river flows would lead
to reductions in these supplies.
o By 2010, approximately 3 to 8 gigawatts would be needed to
meet the increased demand, and by 2055, 23 to 48 GW would be
needed an 8 to 11 percent increase over baseline additions
that may be needed without climate change. These additions
would cost $23 to 35 billion by 2055.
Policy Implications
o U.S. and Canadian policy makers, though such institutions as
the International Joint Commission and other institutions,
5-3
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Great Lakes
should consider the implications of many issues for the
region. This study raises additional issues concerning:
The water regulation plans for Lake Ontario and
possibly for Lake Superior lake levels.
The potential increased demands for diverting Great
Lakes water for uses outside of the basin. Before
such a potential demand could be accommodated,
additional analysis would be required. This is not
currently allowed by federal statutes.
Long range industrial, municipal, and agricultural
water pollution control strategies will be affected
by climate change. Agencies such as EPA may wish to
examine the implications for long-term point and non-
point water pollution control strategies.
The research, planting, and land purchase decisions
in northern forests supported research by federal,
state, and private institutions.
CLIMATE-SENSITIVE NATURAL RESOURCES IN THE GREAT LAKES REGION
The Great Lakes region* is highly developed, largely because
of its natural resources. The steel industry developed along the
southern rim of the lakes, in part because iron ore from the
north could be inexpensively transported over the lakes. Rich
soils, moderate temperatures, and abundant rainfall have made the
southern part of the region a major agricultural producer.
Forests are abundant in the north and support commercial and
recreational uses. The basin has become the home of over 29
million Americans and produces 37% of U.S. manufacturing output
(U.S. EPA, 1987; Ray et al.). Although these resources provide
many benefits, they are also quite vulnerable to climate changes,
oftentimes with negative impacts upon society.
Current Climate
The Great Lakes region has a mid-latitude continental
climate. Winter is sufficiently cold to produce a stable snow
cover on land and ice on the lakes. Average January temperatures
over Lake Superior are -15°C (5°F), and the average July
*This chapter will cover only the U.S. side of the Great Lakes
and the eight States bordering on them (see Figure 5-1).
5-4
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Chapter 5
temperatures in the southern part of the region are 22°C (72°F).
The average rainfall varies from 700 to 1,000 mm (27 to 39
inches), depending on location (Cohen, in Giantz Volume _).
The Lakes
The Great Lakes are a system of five major lakes that
contain approximately 18% of the world supply of freshwater and
95% of the freshwater in the United States (U.S. EPA and
Environment Canada, 1987) (see Figure 5-1, Map of Great Lakes).
The natural flow of the lake system begins in Lake Superior, the
largest of the lakes, which drains via the St. Marys River into
Lakes Michigan and Huron.* Water from Lakes Michigan and Huron
flows out through the St. Clair River into Lake St. Clair. From
there, the water flows through the Detroit River and into Lake
Erie, the shallowest lake. The Niagara River connects Lakes Erie
and Ontario, and the system ultimately empties into the Atlantic
Ocean via the St. Lawrence River and Seaway.
The greatest influence on lake levels is nature. Seasonal
fluctuations are on the order of 0.3-0.5 m, with the lakes
peaking in late summer because of condensation over the northern
lakes and reaching minimum levels in late winter. Interannual
lake level changes have been much larger, approximately 2 m.
Lake Regulation
The flow between the lakes is controlled by dams at two
points: (1) the St. Mary's River to control levels of Lake
Superior; and (2) Iroquois, Ontario, to control Lake Ontario.
The major diversion out of the lakes is the Chicago diversion,
which transfers water from Lake Michigan through the Illinois
River into the Mississippi River. Man's influence on lake levels
is relatively small. Doubling the flow down the Chicago
diversion would lower lake levels only by 2.5 inches in 15 years
(Quinn, 1987).Joint control of lake supply was codified in the
Boundary Waters Treaty of 1909 between Canada and the United
States, which created the International Joint Commission (IJC)
consisting of representatives from both countries. The IJC
regulates flow through the control structures and diversions by
balancing the needs of shipping, hydropower, and consumptive uses
among the lakes and along the St. Lawrence River and Seaway. Two
regulatory plans (Plan 1977 for Superior and Plan 1958D for
Ontario) set ranges of levels between which Lakes Superior and
Considering a single hydrologic unit because they are
connected by the Straights of Mackinac.
5-5
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/\%
Cornwall
\
]
<
X^'**w
Forest Sites
Compensating Works
Agriculture Sites
Jt Shipping Sites
Figure 5-1. Map of the Great Lakes studies.,
5-6
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Chapter 5
Ontario must be maintained. Diversion out of the lakes is also
limited by law. Flow through the Chicago diversion was limited
by the Supreme Court to 90 m/s (3,200 ft3/s) (Tarlock, 1988),
and the 1986 Water Resources Development Act forbids diversion
out of the lakes' basin without the consent of all Great Lakes
governors (Ray et al.).
Climate-Sensitive Uses of the Lakes
Shipping
The U.S. Great Lakes fleet, which consists of approximately
70 ships, transported over 171 million tons of cargo in 1987 (New
York Times). The tonnage of U.S. shipping consists of iron ore,
coal, and limestone, all primary inputs for steel (77%); lake
grain (13%); and petroleum products, potash, and cement (10%)
(Nekvasil, 1988) Cargo volumes are displayed in Table 5-1. Most
of the goods are shipped within the Great Lakes, with only 7% of
the tonnage (mainly grains) shipped to overseas markets (Ray et
al.). Although shipping activity had declined as a result of
reductions in U.S. steel production, recent increases in steel
output have lead to additional demand for shipping (Agar, 1987;
New York Times)...
Great Lakes ships last over half a century and are designed
to pass within a foot of the bottom of channels and locks. Cargo
capacity is quite sensitive to lake and channel depth because of
this low clearance. The presence of ice usually shuts down Great
Lakes shipping up to 4 months each year.
Table 5-1. Cargo for U.S. Great Lakes Shipping in 1987
(thousands of tons)
Cargo Weight
Iron Ore 61,670
Coal 37,731
Stone 33,164
Grain 22,338
Petroleum Products 11,491
Cement 3,806
Potash 1.702
Total 171,902
Source: Nekvasil (1988).
5-7
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Great Lakes
Hydropower
The eight Great Lakes States use the connecting channels and
the St. Lawrence River to obtain 35,435 gigawatt hours of
hydropower each year, which is about 5% of their electricity
generation. About four-fifths of the hydropower is produced in
New York State, which derives over 26% of its electricity from
hydropower (Edison Electric Institute, 1987).
Municipal Consumption
Most water used for the domestic and industrial consumption
in the basin is taken from the lakes. Surface waters supply 95%
of the basin's water needs. By the year 2000, consumption is
estimated to increase by 50 to 96% (Ray et al.; IJC, 1985).
Fisheries
In 1984, the value of the harvest to the U.S. commercial
fishing industry was approximately $15 million (U.S. EPA and
Environment Canada, 1987; Statistical Abstract of the United
States, 1987). Although most fishing in the Great Lakes is for
recreation, fisheries are managed by the States, although the
Great Lakes Fishery Commission coordinates activities among the
States.
Tourism
Three National and 67 State parks are located along the
shores of the lakes, as are numerous local parks. Over 63
million people visited these parks in 1983. (Ray et al.; Great
Lakes Basin Commission, 1975). In 1984, lake-generated
recreation produced $8 to 15 million in revenues. Fishing,
boating and swimming are very popular.
Shoreline Development
Over 80% of the U.S. side of the Great Lakes shoreline is
privately owned. One of the most developed shorelines is the
101-km Illinois shoreline, where many parks and residential
buildings, including apartment houses, are built near the water's
edge. Shoreline property owners have riparian rights to use
adjoining waters. The shoreline property owners cannot
substantially diminish the quantity or quality of surface waters
(Ray et al.).
5-8
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Chapter 5
Climate and Water Quality
Water quality is directly affected by climate. Lower stream
runoff increases concentrations of pollutants. Every summer, the
lakes stratify into a warmer upper layer and a cooler lower
layer. This stratification can limit biological activity by
restricting the flow of nutrients between layers. In addition,
warm temperatures and an excess supply of nutrients (phosphorous
and other chemicals from agricultural runoff and sewage effluent)
can lead to algal blooms which decay and cause a loss of oxygen
(eutrophication) and reduction in aquatic life in the lower
layers of lakes such as Lake Erie. Cool weather and the
formation of ice help to deepen the mixed layer and break up the
stratification and thoroughly mix the lakes in the winter.
Development, industrialization, and intensive agriculture in
the Great Lakes Basin has created serious pollution in the lakes,
especially Lake Erie. In the early 1970s, nutrient loadings were
so high that Lake Erie experienced significant eutrophication
problems for several years (DiToro, 1987).
Two measures have helped improve water quality. The
U.S.-Canada Great Lakes Water Quality Agreement of 1972 called
for controlling nutrient inputs and eliminating the discharge of
toxic chemicals, and the Clean Water Act mandated construction of
sewage treatment plants and controls on industrial pollutants.
The United States and Canada spent a total of $6.8 billion on
sewage treatment in the Great Lakes. By 1980, nutrient loadings
into Lake Erie had been cut in half (Ray et al.; DiToro, 1987),
and water quality had markedly improved.
Fluctuating Lake Levels
Recent high and low lake levels have significantly affected
users of the lakes. In 1964, Lake Michigan was 0.92 m below
average, making some docks and harbors unusable. Shipping loads
were reduced by 5 to 10% and more shipments were required,
subsequently raising the cost of raw materials and supplies by 10
to 15%. In addition, many water intakes had to be extended or
lowered (Changnon). Flow through the Niagara hydropower project
fell by more than 20%, with electricity generation off by more
than 35%. Flow through New York's St. Lawrence hydro project was
more than 30% below its mean, with electricity generation
decreased by 20% (Linder, 1985). Low lake levels also provide
benefits: as beaches have become enlarged, their use and
enjoyment have increased.
5-9
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Great Lakes
The low water levels in the 1960s exposed the supporting
structures along Chicago's shoreline to air, causing dry rot.
When lake levels rose to record height in the 1980s, the wood
pilings and sections of the revetment collapsed. Apartment
houses that were built too close to the shoreline during the low
levels of the 1960s were flooded, as were roadways built close to
the shore. The estimated construction cost for rebuilding the
damaged shoreline protection system is $843 million (Changnon).
The last 2 years have been relatively hot and dry, causing lake
levels to recede to average levels. The lower levels have forced
shippers to reduce tonnage just as the steel industry in the
region is undergoing a resurgence.
Land Around the Lakes
The land in the Great Lakes region is extensively used for
industry, agriculture, and forestry. Many of the uses are
sensitive to climate.
Land Uses
Urban Development
Approximately 29 million people live in the Great Lakes
Basin, mostly in the urban areas around the cities on the
southern edge of the Great Lakes: Chicago, Detroit, Cleveland,
Toledo, and Buffalo. Many of the residents work in manufacturing
industries, which despite recent declines, still provide 23% of
payroll employment (Ray et al.).
Agriculture
Agriculture is the single largest user of land: 42% of all
land in the eight Great Lakes States is devoted to crops, and an
additional 10% is used for pasture. The Great Lakes States
encompass most of the Corn Belt. In 1983, roughly 59% of all
U.S. cash receipts for corn and 40% of the receipts for soybeans
came from this region. Overall, the Great Lakes States produced
26% of the total U.S. agriculture output, or $36 billion.
(Federal Reserve Bank of Chicago, 1985) . Most crops are grown
on dryland as only about 1% of the region's croplands were
irrigated in 1975 (U.S. Department of Commerce, 1987).
Livestock are also important to the agricultural economy of
the region. Approximately 18% of U.S. cattle are raised in these
eight States; of these, 52% are dairy cows (USDA, 1987) . (The
sensitivity of livestock to climate change is discussed in the
Agriculture chapter of this report.)
5-10
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Chapter 5
Forests
The forests in the region have commercial, recreational, and
conservation uses. The forests in the south are mainly oak and
northern hardwoods, such as maple. The north has almost 21
million hectares (ha), (52 million acres), of forests consisting
mostly of northern hardwoods, such as maple, birch, and beech,
and boreal forests, such as spruce and fir trees. The Federal
and State governments own, respectively, 11 and 13% of the
forests in Michigan, Minnesota, and Wisconsin; while over half
are privately owned (USDA, 1982). The pulp, construction, and
furniture industries are major consumers of such species as
aspen, pines, balsam fir, spruce, maples, paper birch, and oak.
The forest industry is a major employer in the northern part of
the region. In Wisconsin, for example, 283,000 jobs are in
timber harvesting and manufacturing related to forestry (Botkin;
USEPA arid Environment Canada, 1987). Forestry is' considered to
be a growht industry in the region as Michigan has identified
forest products as one of the three key industries targeted for
expansion in the State (Ray et al.).
PREVIOUS CLIMATE CHANGE STUDIES
The impacts of climate change on many of the systems in the
Great Lakes have been analyzed in separate and unrelated studies.
Canadian researchers have examined the potential impacts of
climate change on Great Lakes levels and have concluded that
levels would fall. Cohen (1986) used hydrologic calculations to
estimate that the lakes might fall between 0.2 and 0.8 m. More
recently, Sanderson (1988) used a hydrologic model of the lakes
also to estimate that the lakes would drop by an average of 0.2
to 0.6 m. Wall (1985) concluded that lower lake levels could
reduce ecological diversity and dry up enclosed marshes. In
another study, Cohen (1987) estimated that withdrawals of water
from the lakes for municipal consumption would increase by about
2.5% on an annual basis and would only marginally affect lake
levels.
Assel et al. (1985) studied the extent of ice cover during
the winter of 1982-83, which had temperatures 3.3-4.4"C warmer
than the 30-year mean. They found that ice cover on Lake
Superior was reduced from a normal 75% coverage to 21%. On Lake
Erie, ice coverage was down to 25% from the normal 90%. Meisner
et al. (1987) conducted a literature review on the possible
effects of global warming on Great Lakes fish. Results are
discussed in the fisheries section of this chapter.
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Great Lakes
Linder (1987) used the GISS transient to estimate impacts on
electricity demand and hydropower generation in 2015 in upstate
New York. He found total energy demand declining by 0.21-0.27%,
but peak demand increasing by 1-2%. Meanwhile, hydropower
production could decline between 6 and 8.5% owing to reductions
in streamflow.
Impacts on managed and un-managed vegetation have also been
studied. The Land Evaluation Group examined the potential
impacts of climate change on agriculture in Ontario and found
that yields could decrease in southern Ontario and farming could
become feasible in northern Ontario. The study also indicated
that the direction of change for yields depends on whether
rainfall increases or decreases (Land Evaluation Group, 1986).
Solomon and West (1986) used a stand simulation model (see forest
section of the chapter) to estimate impacts of doubling and
quadrupling of C02 levels on a northwest Michigan coniferous-
deciduous transitional forest. They found that doubled C02 would
lead to an eventual disappearance of boreal forests and an
increase in deciduous trees. Total biomass would decline at
first and rebound in about two centuries.
Two studies by Canadian researchers examined the possible
impacts of climate change on tourism and recreation in Ontario.
Both studies used climate change scenarios based on the GISS and
GFDL models (although these may have been earlier model runs).
Crowe (1985) estimated that snowfall would decrease by 25-75%,
and the ski season in southern Ontario would be cut by 75-92% (7-
12 weeks) and 13-31% (2-4 weeks) in the north. Wall found
similar results. He concluded that reduced snowfall could
eliminate skiing in southern Ontario and would shorten the
northern Ontario ski season by 30-44%. A longer summer season
could increase such summer tourism activities as camping. Wall
(1985) also thought that lower lake levels could decrease
ecological diversity and dry up enclosed marshes.
GREAT LAKES STUDIES IN THIS REPORT
Unlike previous studies, the studies for this report used
common scenarios to address some of the potential impacts of
climate change on a number of natural and societal systems in the
Great Lakes region. The studies address the direct effects of
climate change on the resources and some of the indirect effects
on infrastructure and society. They focused on the lakes
themselves, examining such issues as lake levels, ice cover,
thermal structure, and fisheries. They also looked at the
effects of these changes on shipping and shoreline properties,
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Chapter 5
and examined the sensitivities of agriculture and forest to
climate change. Finally, the studies examined the implications
of climate change for Great Lakes policies and institutions.
Some of the studies were linked quantitatively, but most were
conducted independently of each other.
The studies involved either new topics or approaches that
were not used in previous studies. For example, the analysis of
lake levels used a more complex hydrologic model than was used
previously. The agriculture analysis complements the Land
Evaluation Group's study of Ontario by using a different model to
examine impacts on the U.S. side of the lakes. The potential
impacts of climate change on thermal structure were examined for
the first time. Also for the first time, models were used to
analyze impacts on fisheries. This study complements previous
studies on forests by using a combination of modeling techniques
to test the similarity of results.
The following analyses were performed for this report:
Direct Effects on Lakes
o Lake Levels - Croley and Hartmann, Great Lakes
Environmental Research Laboratory.
o Ice Cover - Assel, Great Lakes Environmental Research
Laboratory.
Impacts of Lake Changes on Infrastructure
The results from the first two studies were used in the
following studies:
o Great Lakes Shipping - Keith, DeAvila, and Willis,
Engineering Computer Optecnomics, Inc.
o The Impacts of Low Lake Levels on the Illinois
Shoreline - Changnon, Leffler and Shealy, Illinois State
Water Survey.
Water Quality
The following studies concern water quality and the effects
on aquatic life in the lakes. The first two studies examined the
direct effects of climate on the thermal structure of some of the
lakes.
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Great Lakes
o Thermal Structure of Southern Lake Michigan - McCormick,
Great Lakes Environmental Research Laboratory.
o Eutrophication of the Central Basin of Lake Erie -
Blumberg and DiToro, Hydroqual, Inc.
The results from these studies were used in the following:
o Great Lakes Fisheries - Magnuson, Regier, Sheeter, Hill,
Holmes, and Meisner, Universities of Wisconsin and
Toronto.
Forests
A series of studies on forests was commissioned to examine
shifts in ranges, transient impacts, and the potential for
migration of some Great Lakes forests. Basically, these are
different analytic techniques for understanding how climate
change may affect the composition and abundance of forests in the
region.
o Transient Effects on Great Lakes Forests - Botkin,
Nisbet, and Reynales, University of California at Santa
Barbara.
o Forest Migration - Zabinski and Davis, University of
Minnesota.
o Ecological Response Surfaces - Overpeck and Bartlein,
Lamont-Doherty. (Regional results will be taken from this
study.)
Agriculture
The potential changes in agriculture in the Great Lakes were
analyzed by studying changes in crop yields in the region and
integrating the results in a national analysis of production
changes. That national analysis was used to determine if
production in the region could increase or decrease. The results
of these studies were used to examine potential farm level
adjustments.
o Crop Yields in Great Lakes States - Ritchie, Baer, and
Chou, Michigan State University.
o Farm Level Adjustments by Illinois Corn Producers -
Easterling, Illinois State Water Survey.
5-14
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Chapter 5
This chapter will use regional results from the following:
o Economics Effects on Agriculture - Adams, Glyer and
McCarl, Oregon State University.
Energy
This project analyzed potential changes in the national
demand for electricity and estimated changes in regional demands.
Results for the Great Lakes region are presented in this chapter.
o Electric Utilities - Linder and Inglis, ICF, Inc.
Policy
The potential policy implications of the changes indicated
by these and previous studies for local, State, Federal, and
international decisionmaking are examined. This project provided
information for the background and policy implications sections.
Results are not presented as part of the results section.
o The Implications for Policies and Institutions - Ray,
Brah, and Lindland, The Center for the Great Lakes.
GREAT LAKES REGIONAL SCENARIOS
All three GCMs that provide the basis for the climate change
scenarios show rather large increases in temperature for the
Great Lakes region under the doubled C02 climate. The seasonal
and annual temperatures and precipitation are displayed in Figure
5-2. The OSU scenario has an annual temperature rise of 3.5°C,
with no change in seasonal pattern. The GISS scenario is about a
degree warmer on average and has the largest warming in the
winter and fall. The GFDL scenario has the largest warming of
the three models, about 6.5°C annually, with the largest warming
in the summer. All three scenarios have annual increases in
precipitation. OSU has an increase of approximately 0.1 mm/day,
with precipitation rising in all seasons. GISS has an increase
of approximately 0.2 mm/day, with precipitation declining
slightly in the fall. GFDL has an annual precipitation increase
of only 0.05 mm/day, but rainfall drops by 5 mm/day in the
summer. The large temperature increase and small rainfall
increase combine to make GFDL the most severe scenario. This is
especially true in summer months, when GFDL has the largest
temperature rise of any scenario and virtually reduces rainfall
to zero. OSU is the mildest scenario owing to the smaller
5-15
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6
LU
O
O
ill 4
cc
in
-
1
GISS
GFDL
OSU
Q
35
cc
LU
ti
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.1
-0.2
-0.3
-0.4
-0.5
-0.6
NOTE:
NO CHANGE
IN SUMMER
I I WINTER
SPRING
SUMMER
FALL
ANNUAL
GISS
GFDL
OSU
Figure 5-2
Average change in temperature (upper) precipitation
(lower) over Great Lakes grid points.
5-16
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Chapter 5
temperature increase and GISS is in the middle in term of
severity.
One limitation related to using the GCMs as a basis for
climate change scenarios for the Great Lakes region is that the
lakes are not well represented in the GCMs. The relatively large
size of the GCM grid boxes results in little feedback from the
lakes to the regional climate estimates from the GCMs.
RESULTS OF THE GREAT LAKES STUDIES
Lakes
Lake Levels
Geologic records indicate that Great Lakes levels have
fluctuated as paleohistoric climates have been wetter and drier
(Larson, 1985). Recent short-term variations have been the
result of short-term changes in precipitation patterns. Croley
and Hartmann examined the potential impacts of global warming on
average lake levels.
Study Design
Croley and Hartmann used a water supply and lake level model
of the Great Lakes Basin to estimate the potential impacts of
climate change on levels of the Great Lakes (Croley, 1983a,b;
Croley, 1988; Quinn, 1978). This model includes a separate model
for each of the 121 watersheds in the basin. Croley and Hartmann
simulated runoff in each of the sub-basins, overlake
precipitation, and evaporation. Lake levels are very, sensitive
to evaporation; therefore, Croley and Hartmann ran each GCM
scenario with different assumptions about evaporation.*
Finally,they used the current plans (Plan 1977 for Superior and
Plan 1958-D for Ontario) and hydraulic routing models of outlet
and connecting channel flow and estimated water levels on each of
the Great Lakes.
In Volume _, Croley focuses on results from his latest run.
This run includes assumptions that lead to relatively high
amounts of evaporation and larger drops in lake levels. Earlier
runs had less evaporation increases and less of a drop in lake
levels. Results in this chapter include the latest run and an
earlier run.
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Great Lakes
The regulation plan for Lake Superior failed under the GFDL
scenario. To obtain an estimate of changes in levels for
Superior-Huron, St. Clair, and Erie, Croley and Hartmann assumed
that over a 30-year period, total inflows into Lake Superior
(runoff + over-lake precipitation + diversions - evaporation)
would equal total outflows, and Lake Superior levels would not
change. Only 30-year average lake levels were calculated for the
other lakes.
Limitations
The relationships in this model were developed for a cool
and wet climate. The analysis did not account for changes in the
consumptive uses of the lakes (due to population and economic
growth or climate change), and it did not consider changes in the
regulation plans, or increases or additions to diversions into or
out of the lakes. The analysis also used the difference in
vector winds from the GCMs as a proxy for the difference in
sealer winds because GCM estimates of changes of sealer winds
were not available. Thus, the wind estimates probably
underestimate changes in windspeed (Rind, 1988). The uncertainty
on winds is complicated by the uncertainties concerning
evaporation. Different assumptions of evaporation affect the
magnitude of lake level drop, but they do not affect the
direction of change lake levels fall under all evaporation
assumptions.
Results
Lake levels fall significantly under all three scenarios
(see Table 5-2). The lake level changes are displayed in ranges
from low to high evaporation.
Average levels for Lake Superior are about 0.4-0.5 m below
average levels for the 1951-80 period under the OSU and GISS
scenarios. No figure for Lake Superior is given for the GFDL
scenario, since levels were held constant. These average levels
are generally lower than extreme lows of recent history. Even
though precipitation rises in all three scenarios, lake levels
fall, primarily due to the higher temperatures. Apparently, only
a large increase in rainfall or a large decrease in windspeeds
can offset these changes. Lake levels are estimated to continue
fluctuating on an annual basis. Specific estimates of
fluctuation are not discussed here, since climate is assumed to
remain constant.
5-18
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Chapter 5
Table 5-2
2xCC>2 Scenarios: Reduction in Great Lakes Levels
from 1951-80 Averages (meters)
Scenario
Superior
Michigan/Huron
Erie
Ontario
GISS -0.43 to -0.47 -1.25 to -1.31 -0.95 to -1.16 NA
GFDL NA -2.48 to -2.52 -1.65 to -1.91 NA
OSU
-0.39 to -0.47 -0.86 to- 0.99
-0.63 to- 0.80
NA
Transient Scenario
(average rate of change per decade 1980-2060)
GISS-A -0.006
-0.055
-0.04
NA
NA = Not applicable.
Source: Croley and Hartmann, Volume .
Croley and Hartmann also found that the flow in the St.
Mary's increases by less than 1% in the GISS high rainfall
scenario and drops by 13% in the drier OSU scenario for Lake
Superior. The flow in the Niagara is estimated to be reduced by
2-30%. Croley and Hartmann did not estimate the flow of these
rivers for the GFDL scenario.
The lowering of lake levels appears to be correlated with
increased temperatures in the scenarios. All of the doubled CO2
scenarios lead to declines in runoff to the lakes and increases
in evaporation from the lakes. The reduction in runoff is
largely the result of changes in snowpack accumulation and
ablation. Snowpack in the Lake Superior basin is reduced by
one- to two-thirds, and in the other basins, farther to the
south, the snowpack is almost entirely absent. The reduction in
runoff would reduce average streamflow in the basin. These
results appear to be driven mainly by the temperature increase,
since precipitation rises in all scenarios.
Evaporation increases under all model runs. The increase in
evaporation varied under different assumptions about the
relationship of evaporation to meteorology and ranged from 20 to
48%. For a given assumption about evaporation, higher
temperature scenarios generally caused more evaporation. Lake
5-19
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Great Lakes
level reductions could also be higher or lower, depending on
these assumptions.
All of these changes cause a reduction in net basin supply
(the sum of overlake precipitations and runoff minus evaporation)
by 14-68%. The exception to this is the GISS scenario for Lake
Superior. In that scenario, rainfall increases by 18%, leading
to a 1% increase in net basin supply.
The Ontario regulation plan failed under all scenarios,
including the transient run. Under these conditions, the system
would not contain enough water to keep the level of Lake Ontario
and the flow in the St. Lawrence River within ranges currently
specified by the plan. The Lake Superior regulation plan failed
under the GFDL scenario. Although net basin supply in Lake
Superior increased under GISS, the regulation plan would require
increased flow through the St. Mary's River to the water-short
lower lakes, resulting in a net drop in Lake Superior levels.
These results are consistent with other studies done on lake
levels and climate change. Both Cohen and Sanderson agree with
Croley and Hartmann that lake levels would drop under various
climate change scenarios. The other two studies, however,
estimated lake levels would drop less than 1 m. Croley and
Hartmann may have estimated greater changes because they used a
more sophisticated runoff, evaporation, and routing model and
because of different assumptions made about evaporation. Croley
and Hartmann also used a more integrated approach and more
variables from the GCMs. The estimates for GFDL may also be
higher because the GFDL scenario used in this study had a higher
temperature than the GFDL scenarios used by Cohen and Sanderson.
The results of the transient run (GISS A) are expressed as
the average change in lake level per decade and are not
indicative of what would happen in any particular decade. Lake
Superior levels drop only 0.006 m per decade, while the other
lake levels fall 0.04-0.055 m per decade. An extrapolation of
the transient results to the decade of the 2060s (when the GISS A
transient run reaches doubled CO2 climate conditions) results in
lake level reductions less than for the doubled CO2 GISS
scenario. This is because lake levels do not respond immediately
to climate change, but must catch up. By the end of the
transient scenario, the 2050s, lake levels fall by more than 0.05
m per decade.
Croley and Hartmann found that enough heat would reside in
Lakes Superior, Michigan, Huron, and Ontario to maintain water
surface temperatures at a sufficiently high level throughout the
5-20
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Chapter 5
year, so that buoyancy-driven turnovers of the water column may
not occur at all. This could significantly affect lakewater
quality and aquatic life (see McCormick). Croley estimated that
average surface water temperatures, which would be above 0°C,
would significantly reduce ice concentrations.
Implications
Higher temperatures may lead to increased withdrawals of
water from lakes for municipal consumption. If more powerplants
are needed (see Energy Demand), the demand for cooling water will
rise. Climate change may also result in more calls for diversion
of water out of the basin for use elsewhere. However, lake
levels may be lowered even more as a result of higher demand for
withdrawals for use in the Basin owing to population and economic
growth.
Hydropower production would be reduced, as flows through the
St. Mary's, the Niagara, and the St. Lawrence Rivers would fall.
Losses to hydropower were not estimated for the EPA study,
although Linder's earlier work on hydropower losses by 2015 in
New York State showed potential loss of 1600 to 2066 gigawatt
hours (Linder, 1987). Presumably, hydropower losses would be
higher under the doubled C02 scenarios. The impacts of lower
lake levels on wetlands were not estimated, and the impacts on
shipping and on shoreline infrastructure are discussed later in
this chapter.
Lower lake levels and reduced river flow would likely
adversely affect water quality in the Basin. Less water would
allow for reduced dilution of pollutants. Forty-two hot spots
occupy many bays and harbors along .the Great Lakes. These are
contaminated with a wide variety of halogenated organics and
heavy metals, as well as remobilizable nutrients. Lower lakes
may cause emergence and near emergence of these toxic sediments,
through erosion, leaching, oxidization, or volatilization.
Effects of Lower Lake Levels
Coastal infrastructure around the Great Lakes has generally
been built assuming average lake levels would not change. A drop
in levels could make much of the current infrastructure unusable
and necessitate reconstruction. Changnon examined the potential
impacts and adjustments to infrastructure along the 101-km
Illinois shoreline. This study and shipping analysis used the
lower range of the lake level drops from Table 5-2 because
subsequent analyses that gave different lake levels were
performed too late to be incorporated.
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Great Lakes
Study Design
Changnon et al. interviewed experts about the possible
impacts and costs of adjustment along the Illinois shoreline to
the lower lake level estimates described above. Results are
expressed in current dollars.
Limitations
This analysis did not use economic models and did use
current prices. Results are based on expert judgment. Changnon
et al. also assumed that lakes would reach the levels described
above by 2030. Analysis of this assumption indicates that a
doubled CO2 climate may not be reached until the latter half of
the next century. This study examined only the costs of
rebuilding infrastructure and did not examine ecological impacts.
Results
The largest costs appear to accrue to recreational and
commercial harbors (see Table 5-3). The major expenses are
associated with dredging harbors and lowering bulkheads, which
could cost approximately $200-400 million. If lake levels fall
enough, keeping some harbors open (e.g., Waukegan, Illinois) may
not be a cost-effective choice.
Changnon et al. concluded that slips and docks would be only
slightly affected. Many of these probably would have been
replaced anyway and could be set at lower levels as the lakes
fall. (The impacts on commercial shipping in Lakes Superior and
Erie are discussed in the shipping study.)
Intake valves for municipal and industrial consumption could
be exposed and may have to be lowered or moved farther offshore.
Outfalls for stormwater would have to be extended. Changnon et
al. estimated that extending urban water intakes and stormwater
outfalls could cost $16-17 million.
Although the exposure of more land could present some
erosion problems, it could also enlarge many beaches. An
additional 1-2.2 km2 of beaches would be added to the Illinois
shoreline. In all, Changnon et al. estimated that the costs of
adjusting to lower levels of 1.25 to 2.5 m along the Illinois
shoreline, excluding normal replacement of docks and piers, would
be $220-430 million.
5-22
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Chapter 5
Table 5-3. Estimated Economic Impacts of Lowerings of the Levels of Lake
Michigan Over a 50-Year Period (1990-2040).
Costs in millions of 1988 dollars to address future lake levels at
indicated depths below average level of Lake Michigan (1951-1980).
1.25 meters lower 2.5 meters lower
1.
2.
3.
Recreational Harbors
Dredging
Sheeting
Slips/Docks
Commercial Harbors
Dredging
Sheeting/Bulkheads
Slips/Docks
Water Supply Sources
Extending urban intakes
Wilmette Harbor Intake
30 to 50
15
20*
108
38
. 40*
15
1
75 to 100
35
40*
212
38
90*
15
2
4. Beaches
Facililty relocations 1-2 1-2
5o Outfalls for Stormwater
Extensions and modifications 2 4
TOTALS $270 to $292 million* $512 to 540 million
*Some costs could be partly covered by normal replacement expenditures
over the 50-year period of changing level.
Source: Changnon et al., Volume .
5-23
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Great Lakes
Ice Cover
Warmer winters would reduce ice cover on the Great Lakes.
Some analysts have speculated that ice would be completely
eliminated. Assel used a model to estimate the potential extent
and duration of ice cover.
Study Design
Assel developed a statistical relationship between
temperature and ice cover for this study. The models were
developed for the three basins of Lake Erie, for the Lake
Superior Western and Eastern Basins, and Whitefish Bay in Lake
Superior. Whitefish Bay was included because it has the longest
period of ice cover and acts as a choke point on shipping in and
out of Lake Superior. Lakes Superior and Erie represent extremes
in terms of air temperature regimes, lake depth, and heat storage
capacity, and bound the range of potential ice cover changes.
Limitations
Assel's study did not consider the effects of wind and other
variables on ice formation. Implicitly, the analysis assumed
that winds stay the same. Stronger winds would make the ice
season shorter than estimated, and weaker winds (and calmer
waters) would make it longer. The model was built based on the
relatively cool years of the 1960s and 1970s; therefore, the
doubled C02 scenario temperatures are outside the range of winter
temperatures in those years. However, the model simulated ice
duration within 3 weeks of actual ice duration for the warm
winter of 1982-83.
Results
Assel found that although average ice cover might be
significantly reduced, ice would still form on the lakes (Table
5-4). The central basin of Lake Erie now averages 83 days of
ice cover. Ice cover could be reduced to a total of 6-19 days
and ice formations would generally be limited to near-shore and
shallow areas. Whitefish Bay in Lake Superior currently averages
about 115 days of ice cover. Under the doubled CO2 scenarios,
ice duration would be reduced to 69-80 days. Also, the maximum
percentage of Whitefish Bay covered by ice would be reduced from
close to 100% to 70-20%.
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Chapter 5
Table 5-4. Reduction in Ice Cover in Lakes Erie and Superior
(average annual days of cover)
Lake
Erie West
Erie Cent
Erie East
Supr West
Supr East
Supr WFB
Base
1951-80
93
83
97
112
108
115
GISS Transient
2000s 2030s
83
68
79
109
105
111"
51
37
46
86
83
91
Doubled C02
GISS GFDL OSU
26
8
6
46
43
55
23
6
5
24
19
26
35
19
13
75
69
80
Supr = Superior; WFB = Whitefish Bay.
Source: Assel, Volume .
The temperature rise does not appear to be warm enough to
eliminate ice cover on the Great Lakes, but many winters could
have no ice at all. The Lake Erie Central Basin is estimated to
be ice-free from 11 to 22 years out of 30 years, rather than 1
out of 30 years, as estimated for base climate conditions. This
result appears to be sensitive to depth, as estimates indicate
that the deeper Lake Erie East Basin would be ice-free 60-84% of
the time, and the shallow West Basin would be ice-free in 7-17%
of the winters. Lake Superior would have ice cover in virtually
all winters under the scenarios.
Assel found that ice cover reductions during the first 30
years of the transient scenario (model years 1981-2010) are not
significantly different from reductions during the modeled
current conditions. The length and extent of ice cover
noticeably decline, beginning in the second 30 years of the
transient scenario (2011-2040). By the last decade of the
transient scenario, the 2050s, the extent of ice cover is almost
identical to the GISS 2xCO2 coverage.
Croley also found that ice cover would be reduced. His
analysis shows that average surface temperatures on all the lakes
in the winter is above 0°C. Even if average temperatures are
that high, water temperatures in near-shore and shallow areas,
the areas to which Assel said ice would be limited, would be
sufficiently cold to cause ice formation:
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Great Lakes
Implications
Ice cover reductions could have positive and negative
effects. On the positive side, the shipping season would be
extended (see below). Water would flow more freely through
rivers and connecting channels allowing for more hydropower
production in the winter. On the other hand, ice protects some
aquatic life, such as whitefish, and protects shorelines against
the erosive impact of high-energy waves (Meisner et al., 1987).
Shipping
With lower lake levels, ships would have to lower their
cargo, or ports and channels would have to be dredged. However,
the reduced ice cover would allow a longer shipping season. The
additional days of transport may make up for the loss of capacity
on each voyage.
Study Design
Keith et al. studied the potential impacts of changes in
lake levels and ice cover on shipping in six ports: Two Harbors;
Duluth/Superior and Whitefish Bays in Lake Superior; and Toledo,
Cleveland, and Buffalo in Lake Erie. They used the "ECO Great
Lakes Shipping Model," which includes current data on maj or ports
and commercial ships in the Great Lakes, types of cargo, costs of
transport, and operating costs. Keith et al. used lake level
reductions from Croley and Hartmann to study the change in cargo
capacity and costs per ton and they used the change in cargo
capacity to estimate how many days of shipping would be needed to
transport the same amount of cargo as transported at present.
The latter figure was compared to ice duration reductions
estimated by Assel to determine whether the shipping season was
sufficiently extended to allow for transport of the same amount
of annual cargo as currently transported.
Limitations
The analysis did not consider changes in the composition of
the fleet or in the mix and amount of cargo. It also assumed
that demand for shipping of goods did not change, even in
response to availability of shipping. The analysis did not
examine whether goods would shift to or from alternate means of
transportation and how changes in the costs of shipping and in
the shipping season would affect users. Keith et al. also
assumed that channels were not dredged to be deeper. The
analysis is useful for estimating the direction and approximate
magnitude of change.
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Chapter 5
Results
The costs of shipping were estimated to increase due to
lower lake levels. The effect on the cargo load for ships using
the port of Buffalo are displayed in Figure 5-3. Under drops of
0.7-1.0 m in Lake Erie, which are the lake level reductions
estimated by Croley for the OSU and GISS scenarios, cargo
capacity would decrease by about 5-13%, and costs per ton would
rise by the same amount. Croley's estimate from the GFDL
scenario was that Lake Erie would fall 1.65 m (5.4 feet), but the
shipping model does not include lake level drops of more than 5
feet. A drop of 5 feet would decrease cargo capacity per voyage
by 27% and increase costs by 33%. Since lake levels in Lake
Superior were not estimated to fall as much, the corresponding
reduction in cargo capacity for ships on those ports would be in
the range of 2 to 8%.
Sanderson estimated that lake level reduction of 0.2 to 0.6
m would increase Canadian shipping costs by 5%, assuming the
current fleet and mix stayed the same. Although results are not
directly comparable, since Keith et al. examined U.S. flag ships
and ports, while Sanderson studied Canadian ships and ports, the
estimates are of the same magnitude.
Whether the same amount of annual cargo can be transported
depends mostly on how much lake levels drop. If the drop is
sufficiently large, annual tonnage could be reduced. Figure 5-3
also displays the additional days needed to transport the same
amount of cargo as is currently shipped through Buffalo. Under
the approximate 2-3 foot drop of the wetter and relatively cooler
OSU and GISS scenarios, another 15-40 days of shipping are
needed. Assel estimated ice duration in eastern Lake Erie would
be reduced by 84-91 days. Thus, under these scenarios, even with
reduced capacity per voyage, there would be enough additional
days of travel to transport even more goods. If lake levels fall
5 feet, which is less than estimated by GFDL, an additional 100
days of transport would be needed to handle the same amount of
cargo. Ice duration in eastern Lake Erie is reduced by 92 days
in this scenario, which would not allow enough time to transport
the same amount of cargo, assuming the current fleet and demand
for transport. The results appear to be more sensitive to
changes in lake levels than reductions in ice cover.
5-27
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Chapter 5
Keith and Willis used current dredging costs to estimate the
cost of dredging the ports to restore current channel depths.
The total costs of dredging the three ports in Lake Erie range
from $26-82 million (1987 dollars).
Implications
Reduction in the tonnage per voyage or increased costs for
dredging would raise shipping costs. However, with a longer
shipping season, users of shipping such as powerplants would not
have to carry large inventories to last through the winter and
own enough land to store those inventories. Besides reducing
costs, this could allow current lakefront storage areas to be
used for other purposes. Whether these savings would offset
higher shipping costs was not examined.
Dredging the ports and channels could degrade the water
quality of the lakes. The sediments in many of these ports are
toxic (which included many of the 42 hot spots), and disposal of
the sediments could be complicated by their toxicity and by the
reduced disposal areas resulting from lower lake levels.
Water Quality
Two studies estimated the temperatures and thermal
structures of southern Lake Michigan and the Lake Erie Central
Basin. The Lake Erie study estimates algal production and changes
in dissolved oxygen levels. The Michigan and Erie analyses are
used by Magnuson et al. to study changes in the thermal habitats
of fish.
Thermal Structure of Southern Lake Michigan
Study Design
McCormick used a one-dimensional thermal structure model
(Garwood, 1977) to estimate the heat content and structure of a
site in south-central Lake Michigan. The model has been
successfully applied to oceans and inland seas and was used by
McCormick to analyze a site 150 m deep. GCM data for windspeed,
temperature, humidity, solar radiation, and cloud cover were
applied to hourly data from 1981 to 1984.
Limitations
McCormick used the years 1981-84 as his base case because
hourly water temperature data are not available for 1951-80.
Three years provide very limited baseline climate variability,
5-29
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Great Lakes
although these years include cold and warm periods. Since the
scenario may underestimate reductions in windspeed from the GCMs
(see the discussion of the limitations of the lake level study),
this analysis may overestimate wind-driven mixing in the upper
layer and underestimate the length of time and degree of
stratification. On the other hand, if the intensity of summer
storm increases, then stratification may be weakened and
shortened.
Results
McCormick estimated that the length of the stratified season
would increase under all three scenarios. Figure 5-4 displays
the mixed layer depth (the thermocline) over an average year.
The higher heat content may cause the lake to begin thermally
stratify, on average, about 2 months earlier than in the base
case (in April as opposed to June). The stratified layers begin
to deepen around late fall, as under current climate conditions.
Surface lake temperatures were estimated to be up to several
degrees higher and warm more than lower levels. There appears to
be a larger warming of the entire water column in the winter,
about 2-3°C, than in the summer, which has a warming of about
2°C. The warmer lake temperatures are consistent with the
studies of Croley and Assel, which suggest that midlake water
will generally be ice-free. The earlier onset of stratification,
reduced winds in the scenarios and greater temperature
differences between lake layers could yield stronger density
differences between upper and lower layers.
McCormick detected a significant decrease in the frequency
of complete mixing of the lakes. The surface layer could be
warmer and more buoyant, making it more difficult for entrainment
and mixing to occur. Temperatures were too warm in the winters
of some years to allow the lake to become isothermal, (the mixed
layer would stay above the botton of the lake akk year) leading
to a year-long stratification. This result is consistent with
Croley's analysis.
Implications
Reduced turnover of the lakes could have serious
implications for aquatic species in the lakes. Mixing of oxygen
and nutrients would be disrupted, possibly affecting the
abundance of life in the lower and upper layers of the lakes.
5-30
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45
a. 90
UJ
Q
135
180
BASE
GISS
GFDL
OSU
I
M
M
J J
MONTH
N
Figure 5-4. Lengthening of thermal stratification of southern
Lake Michigan.
Source: McCormick, Volume .
5-31
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Great Lakes
Eutrophication "of the Lake Erie Central Basin
Nutrient loadings have made many areas of the shallow Lake
Erie eutrophic at times. The shallow western and central basins
of the lake are particularly vulnerable to eutrophication.
Installation of pollution controls in recent years has improved
water quality. Blumberg and DiToro analyzed whether climate
change would have an effect on eutrophication in the Lake Erie
Central Basin.
Study Design
Blumberg and DiToro modeled the thermal structure of the
Lake Erie Central Basin. They developed a thermal model for the
basin, using a modeling framework previously designed by Blumberg
(Blumberg and Mellor, 1983). This model is similar to the one
used by McCormick for southern Lake Michigan. Blumberg and
DiToro then examined the direct effects of changes in the thermal
structure on aquatic life in the basin. The outputs from the
thermal model were fed into a eutrophication model that had been
previously developed by DiToro (DiToro and Connolly, 1980). The
latter model estimates what would happen to dissolved oxygen
levels in the lakes by simulating the interactions between
nutrient availability and plankton activity. The models were
only run using two base years, 1970 and 1975. In 1970, the
thermocline (density gradient between the upper and lower layers)
was deep, and over 60% of the hypolimnion (lower level) in the
Lake Erie Central Basin was anoxic (depleted of oxygen). In
1975, the thermocline was shallow, and less than 10% of the lower
layer was anoxic (DiToro, 1987).
Limitations
Although the two base years encompass a wide range of
baseline anoxic conditions, they do not represent a full range of
climate variability. The analysis did not incorporate the actual
reduction in nutrient loadings from the base years, or the
estimated drop in lake levels from Croley's work. Lower lake
levels would reduce the volume of the lower layer in Lake Erie,
possibly increasing eutrophication. The models were not run for
the winter, but Blumberg and DiToro tested the sensitivity of
results to higher water column temperatures (due to warmer winter
air temperatures) in the spring and found no significant
difference in results. Blumberg and DiToro used the vector wind
estimates from the GCMs, which may overestimate mixing in the
upper layer.
5-32
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Chapter 5
Results
Blumberg and DiToro estimated that the Lake Erie Central
Basin could remain stratified about 2 to 4 months longer than
under current conditions, with the stratified season starting 2
to 6 weeks sooner and ending 2 to 7 weeks later. The temperature
difference between the upper and lower layers of the basin are
estimated to be greater under all scenarios, leading to less
exchange of nutrients across the thermocline. The depth of the
thermocline appears to be most sensitive to estimated changes in
windspeeds. In two scenarios, GISS and GFDL, windspeeds are
generally lower, and the thermocline is about 2 m higher than
current depths. In the OSU scenario, windspeeds are estimated to
increase and the thermocline becomes approximately 1 m deeper
than current levels. A lowering of the thermocline depth by 2 m
in the 25-m-deep Lake Erie Central Basin can reduce the volume of
the lower layer by 20%, limiting total oxygen availability.
All three scenarios generally lead to decreases in dissolved
oxygen levels compared to base case conditions despite
differences in thermocline depth. The increase in area of the
Lake Erie Central Basin that is estimated to become anoxic is
shown in Figure 5-5. Dissolved oxygen levels increase only in
the July 1970 case, and this occurs because the levels were near
zero to begin with. Blumberg and DiToro concluded that the
difference in oxygen content is caused by warmer lake
temperatures, which raise bacterial activity enough to increase
oxygen demand. The enhanced biological activity is combined with
a more intense and longer stratified season to further lower
dissolved oxygen levels. Lower thermocline depths, such as in
the OSU scenario, result in even greater decreases in dissolved
oxygen levels.
The estimated changes in the thermal structure of Lake Erie
are comparable to McCormick's results for southern Lake Michigan.
Both estimated that average temperatures in the water column
would rise, that there would be greater differences in
temperature between the epilimnion and hypolimnion, and that
stratification would last longer. One major difference in the
results is that stratification begins earlier and lasts longer in
Lake Erie and begins earlier and breaks up at the same time as
the present stratification in Lake Michigan. It is not clear
whether this difference is attributable to different lake depths,
surface meteorology used to force the models, or to surface
boundary conditions in the calculations.
5-33
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1970
JULY AUGUST
BASE CASE
9.8%
40.6%
1975
AUGUST
0.0%
ezss 2 co2
11.7%
0.5%
0.0%
«FDL21 CO,
22.8%
94.4%
5.9%
OSU 2 « COZ
55.3%
100%
28.8%
Figure 5-5. Area of central basin of Lake Erie that becomes
anoxic.
Source: Blumberg and DiToro, Volume .
5-34
-------
Chapter 5
Implications
Increased eutrophication could make the Lake Erie Central
Basin uninhabitable for finfish and shellfish during the summer.
This could reduce recreational uses of the lake such as swimming,
fishing, and boating. It also could put more pressure on
reducing sources of pollutants, especially such nutrients as
phosphorous, from point and nonpoint sources.
Fisheries
The Blumberg and McCormick studies show that climate change
would probably raise lake temperatures and reduce oxygen levels
in certain areas. To get an initial sense of what these changes
might mean for Great Lakes fish, Magnuson et al. examined the
potential ecosystem, organism, and population responses to warmer
temperatures.
Study Design
Magnuson et al. estimated changes in fish habitat, growth,
prey consumption, and population for sites in Lakes Erie,
Michigan, and Superior. The work used several approaches and
models to examine the following:
o Changes in ecosystem activity, such as changes in
phytoplankton populations, were estimated by using a
community "Qio" rule (Ruttner, 1931), which assumes that
higher biological activity is associated with higher
temperatures.
o Magnuson et al. used the Blumberg and McCormick thermal
structure studies to estimate the potential effects on
thermal habitats the niche in which temperatures are
tolerable for species of fish. To estimate changes in
habitats, the study used laboratory estimates of the
temperature regimes preferred by fish (Magnuson et al.
1979; Crowder and Magnuson, 1983) and assumed that the
lower layer of the Lake Erie Central Basin is
uninhabitable. This study assumed that fish migrate to
habitable sites when inshore temperatures are too warm.
In addition, using a thermal model for streams (Delay and
Seaders, 1966), the study calculated the change in
habitat for brook trout in a southern Ontario river.
o Magnuson et al. used a food consumption and conversion
model (Kitchell et al., 1977) to estimate the changes in
growth and prey consumption at three near-shore sites in
5-35
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Great Lakes
Lakes Superior, Michigan, and Erie. This analysis
assumed there were no limits on forage availability.
Limitations
The study did not consider changes in species interactions
and prey availability. If prey is not sufficiently available,
fish populations could decline. It did not examine the combined
effects of reduced habitat and greater need for forage in the
summer, which would combine to intensify species interactions.
The analysis did not incorporate impacts resulting from lower
lake levels, such as possible loss of wetlands, and it did not
analyze the aquatic effects of the potential reduction in the
frequency of lake turnover or the impacts of a reduction in ice
cover. The introduction of new species, which could have
negative impacts on. existing fish, was not examined,,
Any uncertainties associated with the McCormick and Blumberg
studies would be carried over into the analysis on habitat.
These changes in the lakes and littoral systems may have negative
impacts on Great Lakes fish. These uncertainties could reverse
the direction of results and lead to more declines in fish
populations than indicated here.
Results
Phytoplankton production, zooplankton biomass, and maximum
fishery yields are estimated to increase 1.25-3 fold with the
biggest increase in phytoplankton production (2 to 3 fold)
(Figure 5-6). The larger increases in biological activity are
generally associated with larger temperature increases. The
increase in phytoplankton provides more forage for zooplankton,
which in turn, provides more forage for fish. The increase in
phytoplankton can also enhance eutrophication, as was estimated
by Blumberg and DiToro.
Magnuson and Regier found that the average annual thermal
habitat for all fishes would increase. This was especially
apparent for cold coldwater fishes such as lake trout, which
could have more than a doubling of habitat (see Figure 5-7). The
major reason for the increase in habitat is that more habitable
waters would be found in the fall, winter, and spring. On the
other hand, hotter temperatures in the summer could decrease
habitats by 2-47%, depending on the temperature rise and species.
The length of stream suitable for brook trout in the summer could
be reduced by 25-33% due to higher temperatures.
5-36
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COLD REGION
COOL REGION
WARM REGION
2
LJJ
(0
PHYTOPLANKTON PRODUCTION
O
O
X
CM
O
H
ZOOPLANKTON BIOMASS
ff
O
FISHERY MAXIMUM SUSTAINED YIELDS
OSU
GISS
GFDL
Figure 5-6. Increases in Great Lakes aquatic productivity.
Source: Magnuson et al., Volume .
5-37
-------
CL
UJ
Q
JAN
Habitat:
MAR
JUN
MONTH
SEP
+ 2"C of optimum temperature
SgggSg + 5°C of optimum temperature
DEC
Figure 5-7. Increase in Great Lakes cold coldwater habitat
Source: Magnuson et al., Volume .
5-38
-------
Chapter 5
Fishes are generally estimated to have increased body size
under the scenarios. Cool and cold coldwater fishes could have
20-70% more growth, and warmwater fishes in warm areas could have
3.2 to 5.7 times greater growth. This assumes that prey
availability increases. If prey availability does not increase,
fish growth would also decrease owing to an inability to
compensate for the increased metabolic costs of living in higher
temperatures. Furthermore, the increased demand for forage may
intensify species interactions and alter the food web structure.
The effects of reduced ice cover and possible reduction in
wetlands on Great lakes fishes was not investigated, although
Meisner et al. concluded that loss of wetlands due to lower lake
levels could reduce spawning, nursery, and feeding grounds for
fish in shallow areas, reducing fish populations (Meisner, et
al., 1987).
Implications
If fish populations increase, there could be beneficial
implications for commercial and recreational fishing.
Presumably, commercial yields and sport fishing .would increase,
although certain species, such as brook trout in streams, may be
reduced. A net increase in fisheries would lead to more
employment in commercial fishing and tourism industries but,
increase the need for maintaining water quality in the lakes.
Increased demand on the forage base by predators and the
introduction of new species could have negative effects, but
these cannot be predicted and must be considered as surprises of
unknown probability.
Forests
Climate change could affect the distribution and abundance
of forests in the Great Lakes region. Overpeck and Bartlein
examined the equilibrium range shift of forests, Botkin et al.
studied transitional impacts on composition and abundance, and
Zabinski and Davis analyzed the ability of trees to migrate along
with a rapidly changing climate.
Potential Range Shifts
Study Design
Overpeck and Bartlein studied the potential shifts in ranges
of forest types over eastern North America. This analysis
suggests where trees are likely to grow in equilibrium 2xCO2
5-39
-------
Great Lakes
climate conditions-. It only indicates the approximate abundance
of different species within a range, what the transitional
effects of climate on forests might be, or how fast trees will be
able to migrate to the new ranges. (See the Forestry chapter of
this report for a discussion of the study's methodology and
limitations.)
Results
Under all three 2xC02 scenarios, the range of spruce, a
major component of the boreal forests, would shift almost
entirely out of the region entirely. Northern hardwoods, such as
birch and northern pine species, would shift to the north, but
would still be in the region. Oak trees, which are mostly found
in the southern part of the region, would be found all over the
region in the warmer conditions. The abundance of prairie forbs
(shrubs) would increase in the region and southern pines could
migrate to the southern part of the region.
Transitional Effects
In contrast to Overpeck and Bartlein, Botkin et al. examined
the transitional effect of climate .change on forests and
equilibrium conditions.
Study Design
Botkin et al. used a model of forest species growth and
competition to estimate the effects of climate change on Great
Lakes forests (Botkin et al., 1972, 1973). This model, which is
known as a stand simulation model, can be used to estimate the
transitional changes in composition and abundance of forests
species in response to environmental changes such as higher "
temperature and precipitation.
Botkin et al. studied two diverse sites in the Great Lakes
region. The first is in Mt. Pleasant, Michigan, a heavily
settled area dominated by northern hardwoods and oaks, where
commercial forests are an important resource. The other site is
in Virginia, Minnesota, an undeveloped area dominated by boreal
forests that have commercial and recreational uses.
Limitations
The model includes all dominant tree species in the northern
United States and assumes that seeds from all these trees are
universally available throughout the region. Species with
predominantly southern distributions are not included; therefore,
5-40
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Chapter 5
the model does not estimate whether they could grow in the region
under the warmer climate. (Overpeck found that southern pines
may migrate into the southern part of the region.) Thus, the
stand simulation model does not accurately estimate migration of
trees, either within the region or from other areas. In
addition, the model does not account for fertilization effects of
C02, although C02 may not have positive effects in the
competitive environment of unmanaged ecosystems (see Botkin).
Botkin's analysis did not account for introduction of new pests
into the region for the possibility of increased frequency of
fires, or the combined impact of changes in tropospheric gas
levels and UV-B radiation.
Results. Botkin et al. found that the abundance of species
could significantly change in three to six decades. Figure 5-8
displays results from the transient scenarios for balsam fir and
sugar maple at the Minnesota site. The basal area of balsam fir
starts to decline in three to six decades. Potential declines in
several decades are also seen in simulations of white cedar and
white birch in the Minnesota site. Sugar maple, which has
negligible basal area in the current climate, starts to exhibit
significant growth.within three decades in both transient
scenarios.
Botkin et al. estimated the doubled CO climate would cause
major changes in forest composition throughout the region.
Results from the Mt. Pleasant site indicate that tree biomass at
dry sites, which now have oak and sugar maple, could be reduced
by 73 to 99% and converted to oak savannas or even prairies.
Relatively wet soil sites might be converted from sugar maple to
mostly oak woodlands with some red maple. Biomass at these sites
could be reduced by 37 to 77%.
In the Minnesota site, the boreal forests could be replaced
by northern hardwood forests, now characteristic of areas to the
south (see Figure 5-9). Relatively dry areas, such as the
Boundary Waters Canoe Area where balsam fir dominates, and upland
areas where white birch and quaking aspen dominate, could be
replaced by forests consisting mainly of sugar maples. Where
currently saturated soils in these upland areas become drier and
better sites for tree growth, wood production may increase.
However, bogs that now contain white cedar could become treeless.
This is because no species which could tolerate warmer
bog conditions are currently in the region. More southerly
species could be transplanted.
5-41
-------
BALSAM riR
Soil 0«p«h a l.Qrn W<»l«r Tobl« 0«plh = O.fim
9
«
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o
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X.
9
M
6
v
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oc
<
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«
QVUW
6000
4000
-
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1980
BASAL AREA
O O NORMAL CLIMATE
GISS TRANSIENT A CLIMATE
A A GISS TRANSIENT B CLIMATE
g»fr
X«\2=-*^o-o-°-o-o-'
~~"~ *"""" *"~ A
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2000 2020 2040 2060 2080
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u
w
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SUCAR MAPLE
' 8000
6000
4000
2000
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19
Soil 0«plh * 1.0m Woltr TobU D«pth = 0.8m
BASAL AREA
O O NORMAL CLIMATE
GISS TRANSIENT A CLIMATE /'
A A GISS TRANSIENT B CLIMATE ,
/*
^* /*
^* ~~ ~* '
i t^to -o o 9 o o o N>
BO 2000 2020 2040 2060 2080
YEAR
(Elev. = 750)
Figure 5-8. Change in forest composition during the next century
for a deep, wet, sandy soil in the Boundary Waters
canoe area.
Source: Botkin et al., Volume .
5-42
-------
NORTHERN MINNESOTA NOW
White Birch Balsam Fir
Bog
J3 Water Table ifc
NORTHERN MINNESOTA UNDER 2XCO2 CLIMATE
Sugar Maple
Sugar Maple
Soil
V^^-^3
N1
* *
it- 3
S/^
/
s
120
100 2
07
80 «
60 |
40 §
-20 °
Water Table
Base of Soil
'Bed rock
Figure 5-9. Effects on northern Minnesota forests (Virginia,
Minnesota).
Source: Botkin et al., Volume
5-43
-------
Great Lakes
In both sites, the biggest decline is seen in the hotter
and drier GFDL scenario. Decreased soil moisture, which is a
result of higher temperatures and reduced rainfall, appears to be
the most significant factor reducing biomass.
Forest Migration
Both Overpeck and Botkin assume that trees would be able to
migrate to new locations (although Botkin does not assume
southern species would be able to migrate into the Great Lakes
region). Zabinski and Davis examined the potential range shifts
of sugar maple, yellow birch, hemlock, and beech currently found
in the Great Lakes region and compared that shift with potential
rates of migration.
Study Design
Zabinski and Davis assumed that tree species only grow in
climate with temperatures and precipitation identical to their
current range. They determined the location of potential
species ranges under the GISS and GFDL scenarios. The climate
values were determined by extrapolating between gridpoints.
Zabinski and Davis examined the potential migration of the
species by assuming that the doubled CO2 climate would not occur
until 2090, and that these species could migrate into new regions
at the rate of 100 km per century.
Limitations
The analysis did not consider competition among species or
whether migratory routes would be blocked. It also did not
analyze soil conditions, nutrient availiability, sunlight, and
other relevant factors about northern areas to determine if trees
would survive there. The assumptions about when doubled C02
climate would occur and the rate of migration are both
optimistic. Doubled C02 climate conditions could occur sooner
than 1990. The rate of forest migration used is double the
maximum rate ever recorded for temperate trees. A faster warming
and slower migration would make it more difficult for forests to
keep up with shifts in range attributable to climate change.
Results
Under the wetter GISS scenario, the potential ranges of
sugar maple, yellow birch, hemlock, and beech move markedly
northward to central Canada. The results for hemlock and sugar
maple are displayed in Figure 5-10. The stippled area shows the
potential range, and the black area shows how far the trees could
5-44
-------
Hemlock
Sugar Maple
Potential Range
Inhabited Range
B
APresent Range
B Range After 2050 Under
GISS Scenario
C Range After 2050 Under
GFDL Scenario
Scale 0 400Km
Figure 5-10. Shifts in range of hemlock and sugar maple.
Source: Zabinski and Davis, Volume .
5-45
-------
Great Lakes
migrate by 2090. Zabinski and Davis found that hemlock, yellow
birch, and sugar maple could become much less abundant in the
parts of Wisconsin and Michigan where they currently grow. Beech
may be completely eliminated from the lower peninsula of Michigan
where it is presently abundant. In addition, the rate of
migration would be slower than the climate change. The trees
would not migrate as far as the northern boundary of the climate
range (the stippled area). The southern boundary will be driven
northward by climate change. Since the shift in climate zones is
faster than the assured rate of migration, the southern boundary
would move north faster than the northern migration rates. The
total range of all four species would be reduced.
Under the GFDL scenario, which is hotter and drier, all four
species are eliminated from the Great Lakes region. Northern
hardwood tree species might be replaced by trees characteristic
of more southern latitudes or by prairie or scrubland. Since the
southern range of the trees moves farther north than in GISS but
the trees migrate no faster, the inhabitated range would be much
smaller than under GISS. Zabinski and Davis found that all four
tree species would be confined to an area in eastern Canada
having a diameter of only several hundred km.
The ability of the four species to survive in more northern
latitudes may depend on whether they could adapt to different day
lengths and soils.
Implications of Forest Studies
All three studies, through different analytic approaches,
agree that the scenarios of climate change would produce major
shifts in forest composition and abundance. Boreal forests would
most likely no longer exist in the region. Northern hardwood
forests might still be present, especially in the north. Much of
the southern part of the region could become an oak savannah or
prairie. Uncertainty exists concerning whether forests will die
back or whether new species will be able to migrate and flourish.
The rapid rate of climate change, coupled with the presence of
urban areas and extensive farmland in the southern Great Lakes
States, may impede migration of southern species into the region.
Such a shift could result in increased soil erosion and decreased
water quality. In addition, higher tree mortality and. drier
soils could increase fire frequency. Increased environmental
stress might increase pathogen-related mortality in plants.
Shifts in forest composition and abundance may have implications
for wildlife in the region.
5-46
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Chapter 5
This shift in species also could have significant impacts on
the commercial forest industry in the region. The industry
currently harvests softwoods for production of pulp, paper, and
construction materials. These species would decline and be
replaced by oaks and maples, which are useful for furniture but
take longer to become fully grown. Red maple, which may be more
abundant in the southern area, is not currently used
commercially. Changes in forest abundance may also affect
tourism.
Agriculture
The agriculture studies combine analyses of impacts on the
region and across the country. Ritchie et al. studied the
potential impacts of climate change on crop yields in the region.
Adams et al. then used the results from this study and other
regional crop yield analyses to estimate economic adjustments by
farmers. Easterling studied how a typical Illinois corn farmer
would try to adapt to climate change.
Crop Yields
Study Design
Ritchie et al. used crop growth models to estimate the
impacts of climate change on yields for corn and soybeans in the
Great Lakes States (Jones and Kiniry, 1986). The two
physiological models examine the direct effects of temperature
and precipitation on crop yields. Ritchie et al. also used
simple estimates of increased photosynthesis and decreased
transpiration to conduct a sensitivity analysis of the combined
impacts of change in weather and CC>2 fertilization on crop
yields. In addition, he studied whether crops currently in
southern areas may mitigate climate effects.
Limitations
The analysis of combined effects is new research and will
need further development and refinement. The model runs use
simple parameters for C02 effects, assume higher atmospheric
concentrations of CO2 than are predicted, and may be
overestimates of crop yields. (See the Agriculture chapter of
this report.)
All the scenarios assumed that soils were relatively
favorable for crops, by having low salinity and no compaction,
and they assumed no limits on the supply of all nutrients. In
addition, the analysis assumed farmers would make no
5-47
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Great Lakes
technological adjustments to improve crop yields. Possible
negative impacts due to changes in storm frequency, droughts, and
pests and pathogens were not factored into this study. The
percentage changes for Duluth are very large because current
yields are very low relative to other sites.
Results
Ritchie et al. found that temperature increases alone could
reduce crop yields everywhere in the region except the
northernmost latitudes, such as Duluth, where yields could
increase depending on rainfall availability. Corn yields could
decrease from 3 to 60% depending on climate and water regime
(dryland or irrigated). However, Duluth, the most northern site,
could see increases of 49-86%. Current dryland and irrigated
corn yields are lower in Duluth than in the more southern sites.
Dryland yields in Duluth under climate change would be equal to
other sites, and irrigated yields would exceed the other
locations.
Dryland soybean yields are estimated to drop by 3-65% in the
region, except in the north. There, dryland yields decrease by
6% under GFDL, but increase by 109% under the wetter GISS. Under
irrigated scenarios, soybean yields in the north increase by 96
to 153%. Even with the increase in output, the soybean yields in
Duluth are still lower than in areas to the south.
Table 5-5.
Effects of Climate Change Alone on Corn and Soybean
Yields in Great Lakes States (ranges are GISS-GFDL
and are % change from base)
Corn
Site
Soybeans
Dryland
Irrigated Dryland
Irrigated
Duluth, MN
Green Bay, WI
Flint, MI
Buffalo, NY
Fort Wayne, IN
Cleveland, OH
Pittsburgh, PA
+49
-7
-17
-26
-11
-26
-22
to
to
to
to
to
to
to
-30
-60
-48
-47
-51
-50
-55
+86
-3
-14
-18
-15
-19
-19
to
to
to
to
to
to
to
+36
-44
-38
-38
-48
-43
-45
+ 109
-3
-6
-21
-2
-16
-13
to
to
to
to
to
to
to
-6
-65
-51
-53
-58
-59
-59
+ 153
+3
+6
+6
0
-1
0
to +96
to -26
to -11
to -6
to -19
to -14
to -13
Source: Ritchie et al., Volume .
5-48
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Chapter 5
The reduction in yields in the south is due mainly to the
shorter growing period resulting from extreme summer heat.
Production in the north is currently limited by the long winter,
so a longer frost-free season results in increased yields.
Ritchie found that the demand for irrigation would rise
between 20 and 173% under the GFDL scenario and up to 82% under
GISS, although some sites under GISS were estimated to have up to
21% reductions in demand of up to 21%.
The combined effects of higher concentrations of C02 and
climate change could increase yields if sufficient rainfall is
available. If it is not, yields could rise or fall. Dryland
corn and soybean yields rise up to 135% under the GISS scenario
and up to 390% in Duluth. In the GFDL scenario, however, yields
fall up to 30% or rise 17%, again, except for Duluth, which has
an increase of 66-163%. Irrigated yields for corn rise and fall
under both scenarios, but irrigated soybean yields rise 43-72% in
the south and up to 465% in Duluth. The combined effects lead to
an estimated reduction in demand for irrigation for corn of 26 to
100% under both scenarios, whereas irrigation needs for soybeans
under GFDL rise by 65-207% and range in GISS from a reduction of
10% to an increase of 32%.
Ritchie found that use of a longer season corn variety could
reduce the negative effects of climate alone, under the GFDL
scenario, but still result in net losses.
It is not clear whether crop yields would rise or fall in
the region. Among other factors, this will depend upon how C02
and climate change combine to affect crop growth and on how hot
and dry the climate becomes. Yields and the potential demand for
irrigation appear to be quite sensitive to rainfall, being higher
under relatively drier scenarios. If climate change is severe
enough, as under the GFDL scenario, yields could fall. In
general, irrigation demand would rise, but some significant
exceptions exist.
Implications. The potential shifts of agriculture northward
are discussed below. Since the demand for irrigation is
generally higher, it could become a more attractive option for
farmers in the region. Whether more irrigation is actually used
will depend on its costs and changes in revenue results.
Regional Shifts
Ritchie et al.'s analysis only estimates changes in
potential yields for the Great Lakes region. How much farmers
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Great Lakes
actually grow will depend in part on what happens elsewhere. If
the relative productivity of agriculture rises, farmers will
probably increase acreage. If productivity falls, they would
most likely cut back. Adams et al. examined how different
regions of the United States may react to potential productivity
changes. Results are presented here for the Great Lakes region
only.
Adams et al. modeled potential nationwide shifts in crops
using the Great Lakes analysis and analyses of shifts in other
regional crop yields. He did the analysis for yields
attributable to climate change alone, and for the combined
effects of climate and enhanced C02 concentrations. Adams et
al's analysis did not account for the effects of climate on
agriculture in other countries. How U.S. and regional
agriculture respond to climate change may be strongly influenced
by changes in relative global productivity and demand. (See the
Agriculture chapter of this report for a discussion of the
study's design and limitations.)
Results. Adams et al. estimates of acreage changes for the
Great Lakes States are shown in Table 5-6. It appears that land
devoted to agriculture in the Great Lakes region would not change
significantly in response to climate change. The results
indicate a slight tendency to increase acreage in the northern
Great Lakes States, although only by small amounts. Land use in
the Corn Belt would most likely be unchanged.
The relative increase in acreage in the north is consistent
with Ritchie et al.'s results. Despite the yield reductions
estimated by Ritchie et al. for the southern Great Lakes States,
acreage would not be significantly reduced.
Table 5-6. Percentage Change in Acreage for Great Lakes States
of Iowa and Missouri
Climate Change Alone Climate and COg
GISS GFDL GISS GFDL
Area (%) (%) (%) (%)
Lake States
Corn Belt
+3
+2
0
-6
%1 +10
-1 -6
5-50
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Chapter 5
Implications
The results of Adams et al. and Ritchie et al. suggest that
northern regions will become more attractive for agriculture,
although more extensive analysis is needed to confirm this
result. The presence of thin, glaciated soils may limit this
shift. If it occurs, such a shift could have significant
implications for development of the north. Additional acreage
could be converted from current uses, such as forests, to
agriculture. Increased erosion and runoff from this additional
acreage would pollute groundwater and streams and lakes in
relatively pristine areas. Enhanced agriculture may increase the
need for more shipping as lower lake levels raise shipping costs.
Adjustments by Illinois Corn Producers
Farmers may make many adjustments to climate change such as
planting different crop varieties, planting earlier in the
season, irrigating, and using different fertilizers. Easterling
examined how a typical corn farmer in Illinois would react to
climate change.
Study Design
Easterling presented several professional crop consultants
with the GISS and GFDL climate change scenarios and with
estimates of corn yields and prices for climate effects alone
from the Ritchie et al. and Adams et al. studies. Based on the
interviews, a set of decision rules were established to estimate
how a typical Illinois corn farmer would alter farming practices
in response to the climate and agriculture scenarios.
Limitations
The climate change scenarios involve climate conditions not
experienced by the experts. Their estimates of how farmers would
respond are not based on experience with similar conditions but
on speculation. The results of the combined climate and C02
sensitivity analyses were not presented to the experts. The
analysis is specifically for Illinois corn farmers and cannot be
extrapolated to other areas or crops.
Results
Easterling found that the degree of adjustment depends on
how much climate changes. Under the wetter GISS scenario,
farmers could make adjustments to help mitigate the impacts of
higher temperatures. Such adjustments could include planting
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Great Lakes
earlier in the spring to avoid low soil moisture levels in the
summer, using full-season corn varieties for earlier planting,
and changing tillage practices and lowering planting densities to
better conserve soil moisture. Under the hotter and drier GFDL
scenario, corn production might not be feasible. Farmers would
likely install irrigation systems; switch to short-season corn,
soybeans, and grain sorghum; and perhaps remove marginal lands
from production. This last conclusion is consistent with the
Adams et al. study.
Implications
Although farmers have a variety of adjustment options to
help cope with climate change, they may have great difficulty
coping with extreme changes such as the dry climate implied by
the GFDL scenario. Use of more irrigation would have negative
implications for water quality, although this would be partly
counterbalanced by any retirement of marginal lands.
Electricity Demand
Study Design
Linder and Inglis estimated the national changes in demand
for electricity for the years 2010 and 2055. They first
estimated the change in electricity demand due to gross national
product (GNP) and population growth, and then factored in demand
changes based on change in climate. The results for the Great
Lakes States are displayed here. The Great Lakes analysis did
not consider any reductions in hydropower production resulting
from drops in lake levels. (See the Energy chapter of this report
for a description of. the study's design and limitations.)
Results
Estimates of changes in annual demand induced by climate
change are displayed in Table 5-7. The results for 2010 are a
range based on GISS transient scenarios A and B, and the results
for 2055 are just for GISS A. A latitudinal difference exists
within the Great Lakes region. In the northern States of
Minnesota, Wisconsin, Michigan, northern Ohio, and upstate New
York, annual demand falls. The reduced demand for winter heating
is apparently greater than the increased demand for summer
cooling. This is true in 2010 and 2055 when scenario
temperatures are, respectively, 1 and 4° higher than the base
case. Annual demand in the southern part of the region (in
Illinois, Indiana, southern Ohio, and Pennsylvania) rises because
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Chapter 5
increased cooling needs are apparently greater than reductions in
heating.
Although annual demand could fall in some areas, new
generation capacity requirements for all utilities in the region
would be higher now because of increased summer cooling needs.
New generation capacity requirements needs are estimated to rise
by 3 to 8% in 2010 and by 8 to 11% in 2055. Whether costs would
rise in the next two decades is not clear. Linder estimated that
under the gradual warming of GISS B, cumulative capital costs in
the region would be reduced by $1.3 billion, while under the more
rapid warming of GISS A, costs would increase by $300 million.
By 2055, costs would rise to $23 to 35 billion under GISS A.
However, the cost to build additional capacity to meet GNP and
population growth without climate change would be $488 to 715
billion.
Table 5-7.
Estimated Change in Electricity Demand Induced by
Climate Change for Great Lakes Utilities (%)
Utility
Annual (2010)
Annual (2055)
Minnesota
Wisconsin
Michigan
Upstate New York
Ohio, north
Ohio, south
Pennsylvania
Illinois
Indiana
Total
-0.2 to -0.3
0.4 to -0.5
-0.2 to -0.3
-0.2 to -0.5
-0.2 to -0.3
0.4 to -0.5
0.4 to -0.5
0.5
0.4
Negligible
-1.2
-2.3
-1.2
-1.3
-1.3
2.1
2.2
2.0
1.9
Source: Linder and Inglis, Volume _ .
Implications
Increased capacity requirements could place additional
stress on the region. Powerplants may need cooling water and may
seek to obtain it from rivers or the Great Lakes. Fossil fuel
plants could add more pollutants to the air. The lake level
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Great Lakes
analysis indicates that hydropower production from the lakes
would be reduced, further increasing the demand for energy from
other sources.
POLICY IMPLICATIONS
Climate change could raise many issues for policymakers in
the region to address. Fundamentally, decisionmakers may have to
cope with water use, water quality, and land management issues.
They will probably have to respond to a decline in water
availability, increased demand for water, poorer water quality,
and shifts in land use, including the possibility of expanded
agriculture in the north.
Most likely, many of the decisions in response to climate
change, especially issues concerning water management,
necessarily will be made on an international basis. Both Canada
and the United States oversee the regulation of the lakes, water
quality, and diversions of water out of the basin.
Water Supply Issues
Lake Regulation
One important issue to be faced by both countries may be
regulation of the lakes. Lower lake levels may require altering
plans for Lakes Superior and Ontario. This would involve
tradeoffs among the needs of shippers, hydropower, shoreline
property owners, and infrastructure, and downstream needs, in
deciding how high to keep the lakes and rivers. For example,
maintaining high water levels in the lakes to support shipping,
hydropower, consumption, and improved water quality would be at
the expense of shipping, hydropower, consumption, and water
quality in the St. Lawrence River. Additional structures to
control the flow on the lakes may be an option. The
International Joint Commission should begin to consider the
potential impacts of climate change on lake regulations in its
long term planning.
Withdrawals
Even without climate change, population growth would
increase demand for water for municipal and industrial
consumption and power generation. Climate change would most
likely intensify the demand for withdrawals from the lakes for
even more uses within and outside the basin. Municipal
consumption would rise (Cohen, 1987) , additional powerplants may
5-54
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Chapter 5
use water from the lakes for cooling purposes, and farmers in the
region may need more water for irrigation.
Others outside the Great Lakes may demand diversion of water
from the basin. The 1986 Water Resources Development Act
prohibit such diversion without the agreement of all Great Lakes
governors and prohibits the Federal Government from studying this
issue. Increased diversion through the Chicago Ship Canal was
requested this summer to raise water levels on the drought-
starved Mississippi River. The U.S. Army Corps of Engineers
rejected the request.
Shipping
Any response to the potential impacts on the shipping
industry may be costly. Possibilities include dredging of both
ports and connecting channels. Dredging could cost tens, if not
hundreds, of millions of dollars. In addition to the high
capital costs of dredging, substantial environmental costs could
be incurred in disposing of dredge spoils contaminated with toxic
chemicals. If dredging were not undertaken, cargo loads would be
lower and would possibly impair Great Lakes commerce.
Pollution Control
Climate change will probably lead to stricter pollution
control to maintain water quality. Reduced riverflow, lower lake
levels, changed thermal structure, and potentially reduced
groundwater supplies may necessitate stricter standards and
additional controls on sources of pollution. A need may exist
for better management of nutrient runoff from farms into shallow
areas, such as the Lake Erie Western and Central Basins. Many
pollution control institutions, such as EPA and State and local
water quality agencies, would have the authority to impose
appropriate controls on polluters.
The water quality problems directly caused by climate change
could be exacerbated by other responses to climate change.
Intensified agriculture in the region could increase runoff,
necessitating more control of nonpoint sources of pollution. If
agriculture in northern areas expands, surface and groundwater
quality in relatively pristine areas may be degraded. Additional
powerplants could add to pollution problems through the use of
more cooling water. Pollution control authorities such as the
U.S. EPA may need to impose more comprehensive controls for those
areas and should consider this in their long-term planning.
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Great Lakes
Fisheries
Although the analysis on fisheries indicates that fish
populations in the Great Lakes would generally increase,
maintaining fisheries may require intensive management. In
productive areas, the possibility of introduction of new species
could mean major changes in aquatic ecosystems. Fisheries
management may be needed to maintain commercially and
recreationally valuable species. The Great Lakes Fishery
Commission may wish to consider the possible implications of
climate change on valuable fisheries and management strategies to
handle these possible changes. Additional pollution controls may
be needed to help maintain fisheries in such areas as western and
central Lake Erie.
Land Use
Shorelines
The potential changes in land availability and uses present
opportunities and challenges. Lower lake levels would open up
new beaches and potential areas for recreation and development,
although high capital costs may be associated with developing
them. These lands could be kept undeveloped to serve as
recreational areas and as protection against fluctuating lake
levels and erosion. Conversely, they could be developed to
provide more housing and commercial uses. Building structures
closer to the shorelines would make them more vulnerable to
short-term rises in lake levels.
How these lands will be used will be decided by local and
State governments as well as private shoreline property owners.
Under the Coastal Zone Management Act, States may identify
coastal zone boundaries and define permissible land (and water)
uses (Baldwin, 1984). Thus, the act could be used to help manage
the use of exposed shorelines.
Lower lake levels and less ice cover may also increase
shoreline erosion, decreasing the value of shorelines and
degrading water quality. The Great Lakes Basin is not included
in the U.S. coastal barrier system, a program that denies Federal
funds for development of designated erosion or flood-prone
coastal barriers (Ray et al.).
Forestry
The potential decline in forests and northward shift in
Great Lakes agriculture raise many land use issues. One
5-56
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Chapter 5
important issue may be how to manage potentially large and rapid
shifts in forest composition. To speed northward colonization,
plantings of the species might be recommended along the advancing
front of suitable climate. However, unsuitable soils and day
lengths shorter than the species can tolerate might limit the
success of such plantings. The forest industry may consider
growing different types of species and producing wood for
different uses, such as for furniture rather than for pulp and
paper. Potential uses of new prairies or savannas could present
challenges.
Agriculture
Although forests may decline, demand for more land for
agriculture in northern areas may grow; however, Adams indicated
this demand may be small and will depend on market forces and
policies. Federal and State land managers as well as local
zoning laws may need to consider that the demand for land use may
change. Rules on these lands could have a major influence on
how, if at all, the north is developed.
Demographic Shifts
This report does not study the demographics associated with
climate change and cannot say whether people will migrate north
along with warmer climates. A workshop on climate change and the
Great Lakes region, conducted by Ray et al. and attended by
Government representatives, academics, and citizens group
representatives who have studied climate-related Great Lakes
resources, concluded that populations from other regions of the
United States could migrate to the Great Lakes. The region could
have a more favorable climate than more southern areas. Although
lake levels may fall, the lakes will still contain a large amount
of freshwater while other areas have more severe water
availability problems. Consequently, the Great Lakes may be
relatively more attractive than other regions.
Like lower lake levels, an in-migration could present
opportunities and challenges. Such a migration could revitalize
the region, reversing population and economic losses of recent
decades. However, it also could exacerbate some of the problems
associated with climate change. More people and industries would
require more water and add more pollution, further stressing
water supplies and quality. Population growth could increase
pressure to develop exposed shorelines along the lakes.
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Great Lakes
CONCLUSION
Climate change could significantly alter the character of
the region. It will be costly to respond to and will require new
rules and laws. Some changes, such as loss of forests and
dependent wildlife, may be irreversible. The lakes are a
precious resource and may become even more valuable when climate
changes. Maintaining their quality may require careful
management of supplies and strengthened efforts at limiting
pollution. Preserving forests and wildlife in a rapidly changing
climate also may be difficult for planners. The challenge for
the Great Lakes region will be to maintain the quality of the
lakes and the surrounding land in response to climate change and
the pressures it brings.
5-58
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Chapter 5
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Cohen, S.J. 1986. The effects of climate change on the Great
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Cohen, S.J. 1987. Projected increase in municipal water use in
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Croley, T.E. II. 1983a. Great Lakes basins (U.S.A. toCanada)
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Crowder, L.B., and J.J. Magnuson. 1983. Cost-benefit analysis
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CHAPTER 6
SOUTHEAST
FINDINGS
Global climate change could affect the Southeast by causing
forests to shift to grasslands, reducing agricultural
productivity and increasing the abandonment of farms, diminishing
fish and shellfish populations, and increasing electricity demand
higher than the national average. Approximately 90 percent of
the national coastal wetland loss and two-thirds of the national
shoreline protection costs due to climate change could occur in
the Southeast. The impacts on rivers and water supplies are
uncertain.
Agriculture
o Southeastern agriculture is generally more vulnerable to
heat stress than to freezing, so the adverse impacts of more
hot days would offset a longer growing season.
o Due to climate change alone, yields of soybeans and corn
would vary from no change in the cooler regions to up to a
decrease of 91 percent in warmer areas, even if rainfall
increases. When climate and the direct effects of CO2 are
considered, yields still drop in states such as Alabama and
Mississippi due to extreme temperatures. Elsewhere, if
rainfall rises, yields may increase. Increased C02 could
also affect weeds, but these impacts were not analyzed.
o If rainfall decreases, irrigation would become necessary for
farming to remain viable in much of the region.
o The range-of such agricultural pests as potato leafhoppers,
sunflower moths, and black cutworms could move north by a
few hundred kilometers. This would most likely result in
changes in the uses of pesticides.
o Considering various scenarios of climate change and CO2, the
productivity of southeastern agriculture could decline
relative to northern areas, and 10 to 50 percent of the
region's farmland could be withdrawn from cultivation. The
decline in cultivated acreage may tend to be concentrated in
areas where farming is currently marginally profitable.
6-1
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Southeast
Forests
o There may be a significant dieback in southern forests.
Higher temperatures and drier soils may make it impossible
for most species to regenerate naturally and may cause
forests to convert to grassland. The decline in the forests
could be noticeable in 30 to 80 years depending on the site
and scenario. Southern non-coastal areas, such as Atlanta
and Vicksburg, may have particularly large reductions.
Relatively cool northern forests, such as those in
Tennessee, may survive, although with some losses.
o The forest industry, which has infrastructure in main
coastal areas and which is structured around currently
valuable tree species, would have to either move or invest
in new commercial tree species.
o Historically, abandoned farms have generally converted to
forests. If large portions of the Southeast can no longer
support the natural generation of forests, the character of
the Southeast's landscape could gradually resemble that of
the Great Plains.
Water Supplies
o Whether river flows and water supplies in the Southeast
would increase or decrease cannot be determined because of
uncertainties in precipitation and minimal snow pack. Water
supply is very important for agricultural, recreational, and
industrial uses. Any decrease in rainfall could disrupt
recreation, hydropower, power plant cooling, and dilution of
effluent, while more rainfall could increase the risk of
flooding.
o For the scenarios used in this report, changes in
operating rules for managed water systems would allow
current water demands to be met in some instances.
Sea Level Rise
o A one-meter rise in sea level by the year 2100 would
inundate 30 to 90 percent of the region's coastal wetlands
and flood 2,600 to 4,600 square miles of dry land, depending
on the extent to which people erect levees to protect dry
land from inundation. Louisiana alone would account for 40
percent of national wetland loss, assuming current river
management practices continue.
6-2
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Chapter 6
o Holding back the sea by pumping sand or other measures to
raise barrier islands and protecting mainland areas with
bulkheads and levees, for a one-meter rise would cost
approximately $42 to $75 billion by the year 2100.
Marine Fisheries
o Gulf Coast fisheries could be negatively affected by climate
change. A loss of coastal wetlands due to sea level rise
could eliminate critical habitats for shrimp, crab, and
other commercially important species. Warmer temperatures
in the Gulf Coast estuaries will be at or above the thermal
tolerances for commercially important finfish and shellfish,
such as shrimp, flounder, and oysters. Oysters and other
species could be threatened by the increased salinity that
will accompany sea level rise.
Electricity Demand
o The annual demand for electricity in the Southeast could
rise by 14 to 22 billion kilowatt hours (2 to 3 percent) by
2010 and by 100 to 197 BKWH (7 to 11 percent) by 2055
because of increased temperature.
o By 2010, approximately 7 to 16 gigawatts would be needed to
meet the increased demand, and by 2055, 56 to 115 GW would
be needed a 24 to 34 percent increase over baseline
additions that may be needed without climate change the
cumulation costs would be $77 to $110 billion by 2055.
Policy Implications
o Federal laws constrain the Corps of Engineers and other
water resource managers from rigorously considering trade-
offs between many nonstatutory objectives of federal dams in
the Southeast, including recreation, water supply, and
environmental quality. Increased flexibility would improve
the ability of these agencies to respond to and prepare for
climate change.
o Strategies now being evaluated by the Corps of Engineers to
protect coastal wetlands in Louisiana may need to consider a
sea level rise of 0.5 to 2.0 m in order to prevent wetlands
from being lost. Measures that would enable this ecosystem
to survive would require major changes in federal navigation
and river flow policies.
6-3
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Southeast
Given the potentially important impacts on forests, agencies
such as the U.S. Forest Service and state agencies, and
private companies may wish to assess the potential for large
losses of southern forests and the implications for research
and management strategies.
CLIMATE AMD THE SOUTHEAST
The climate and the coastal zone of the Southeast are among
the chief factors that distinguish the southeastern United States
from the rest of the nation.* The warm temperatures, abundant
rainfall, and generally flat terrain gave rise in the 17th
century to a strong agricultural economy with a distinctive
regional culture. The combination of a benign climate and 60% of
the nation's ocean beaches continues to attract both tourists and
new residents to the southeastern coastal plain. Florida, for
example, is the nation's fastest growing state and will be the
third largest by the year 2000. (Meo, Volume _).
The projected change in climate, however, could severely
disrupt life in this region. Cities that already are
unpleasantly hot during the summertime would become hotter, with
corresponding increases in air-conditioning demands and electric
bills. Fisheries would be threatened by the hotter estuarine
temperatures and the loss of coastal wetlands. Rising sea level
would erode beaches, inundate wetlands, exacerbate coastal
flooding, and increase the salinity of estuaries, aquifers, and
wetlands.
CLIMATE SENSITIVE RESOURCES OF THE SOUTHEAST
Water Resources
When statewide averages are considered, each of the seven
states in the Southeast receives more rainfall than any other
state in the continental United States. Moreover, the rivers of
the Southeast drain over 62% of the nation's lands, with the
Mississippi River draining 38% of the nation (Geraghty et al.,
1973) .
*Except for the discussion of the economic implications for
agriculture, the term "Southeast" refers to the study area shown
in Figure 6-1: North Carolina, South Carolina, Georgia, Florida,
Alabama, Mississippi, Tennessee, and the coastal zones of Louisiana
and Texas.
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Southeast
The Southeast supports 50,000 square miles (mi2) of ^
bottomland hardwood forests (Mitch and Gosselink, 1986),** which
are periodically flooded areas that offer winter habitat
formigratory birds such as ducks, geese, and songbirds. Bass,
catfish, and panfish are found in the slow-moving rivers, and
trout inhabit the fast-moving mountain streams.
Dams have been constructed along most of the region's major
rivers. Although private parties have built a few dams, most of
the major projects were built by the U.S. Army Corps of
Engineers, the Tennessee Valley Authority, and other federal
agencies. In general, these reservoirs have been designed for
the following statutory purposes: to ensure a sufficient flow of
water during droughts; to prevent floods; and to the extent that
this purpose does not conflict with the previous objectives, to
generate hydropower. .The nonstatutory objectives of
environmental quality, recreation, and water supply also are
considered in the operation of dams. Dam construction has
created large lakes along which people have built houses, hotels,
and marinas. These dams generate 22.2 billion kilowatt hours
(kWh) per year, approximately 7% of the region's power
requirements (Edison Electric Institute, 1985). In general, the
reservoirs have sufficient capacity to retain flood surges and to
maintain navigation flows during the dry season. The one notable
exception is the Mississippi River: levees and land-use
regulations are the main toos for preventing flood damages;
although the Mississippi's base flow usually is sufficient to
support navigation, the navigation on navy stretches of the river
was impeded during the drought of 1988.
In Florida, which accounts for 45% of southeastern water
consumption, groundwater supplies about half the water used by
farms and 85% of the water use for residential and industrial
purposes. For the rest of the Southeast, groundwater supplies
most water for agriculture and rural uses but only 30% for public
supplies.
Atlanta and some other metropolitan areas derive their water
supplies from Federal reservoirs. Many cities that do not obtain
water from Federal reservoirs still benefit from Federal and
Federal/State water management. For example, New Orleans obtains
its water from the Mississippi River. Without the Old River
Control Structure in Simmesport, Louisiana, which prevents the
river from changing its course to the Atchafalaya River, the New
Orleans water supply would be salty during droughts. Although
Miami obtains its water from the Biscayne aquifer, some coastal
wells would be salty without the efforts of the U.S. Army Corps
This measure includes MS, AK, LA, TX, and VA.
6-6
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Chapter 6
of Engineers and the South Florida Water Management District to
recharge the aquifer with supplemental freshwater from canals and
Lake Okeechobee.
The various uses of water often conflict with each other.
Hydroelectric power generators and lakefront property and boat
owners benefit when water levels are maintained as high as
possible. However, high water levels make flood control more
difficult, and summer releases for navigation, hydropower, and
environmental quality require that lake levels be lowered during
the dry season.
Estuaries
Over 43% of the fish and 70% of the shellfish harvested in
U.S. waters are caught in the Southeast (Fishery Statistics
Division, NOAA, 1987). Commercially important fishes are
abundant largely because over 85% of the nation's coastal
wetlands are found in this region; over 40% are found in
Louisiana alone.
Most of the wetlands in the Southeast are less than 1 meter
(m) above sea level. The wetlands in Louisiana are already being
lost to the sea at a rate of 50 mi2 per year due to the
interaction of human activities and current rates of relative sea
level rise resulting from the delta's tendency to subside 1 cm
per year.
Summer temperatures in many of the gulf coast estuaries are
almost as warm as crabs, shrimp, oysters, and other commercially
important fishes can tolerate (Livingston, Volume ). Winter
temperatures along the Gulf coast are almost warm enough to
support mangrove swamps, which generally replace marshes once
they are established; mangroves already dominate the Florida
coast south of Fort Lauderdale.
Beach Erosion and Coastal Flooding
The Southeast has 1,100 miles of sandy ocean beaches, many
of which are found on low and narrow barrier islands. The
Atlantic coast is heavily developed; while much of the gulf coast
is only now being developed. In part because of their
vulnerability to hurricanes, none of Mississippi's barrier
islands has been developed, only one of Louisiana's barrier
islands has been developed. Because much of Florida's gulf coast
is marsh, it is still largely undeveloped.
6-7
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Southeast
All eight coastal states are experiencing coastal erosion.
Along developed coasts, recreational beaches have narrowed,
increasing the vulnerability of shorefront structures to storms.
In Louisiana, some undeveloped barrier islands are eroding and
breaking up. Elsewhere, narrow barrier islands are keeping pace
with sea level rise by "overwashing" (i.e., rolling over like a
rug) in a landward direction, while wide islands and mainland
coasts have simply eroded. The coastal states of the Southeast
are responding by holding back the sea in some areas and by
adapting to erosion in others.
The two greatest natural disasters in U.S. history resulted
from floods associated with hurricanes in Galveston, Texas, and
Lake Okeechobee, Florida, in which over 8,000 people drowned.
After the Mississippi River overflowed its banks and
inundated most of coastal Louisiana in the 1930s, Congress
directed the Corps of Engineers to initiate a major Federal
program of flood control centered around the Southeast.
Nevertheless, flood waters often remain over some low areas in
Louisiana and Florida for several days after a major rainstorm.
Hurricanes continue to destroy recreational development in
at least a few ocean beach communities almost every year in the
Southeast. The region presently experiences the majority of U.S.
coastal flooding and probably would sustain the worst increases
in flooding as a result of global warming. Unlike the Northeast
and Pacific coasts, this region has wide low-lying coastal plains
and experiences several hurricanes annually. Each year, storms
destroy recreational development in at least a few ocean beach
communities. Florida, Texas, and Louisiana account for 62% of
the $144 billion of private property insured by the Federal Flood
Insurance Program.
Agriculture
In the last few years, droughts and heat waves have caused
crop failures in many parts of the Southeast. Unlike many of the
colder regions, cold weather is generally not a major constraint
to agricultural production, except for Florida's citrus industry.
Although cotton and tobacco were once the mainstays of the
Southeast's economy, agriculture now accounts for only 1% of the
region's income (Bureau of Economic Analysis, 1986). Since World
War II, substantial amounts of farmland have been withdrawn from
agriculture, and much of this land has been converted to forest.
The cotton crop has largely been lost to the irrigated Southwest,
and although tobacco remains profitable, it is grown on only 1/2
million acres. However, in the last few decades, southeastern
farmers have found soybean growth to be profitable; soybeans now
account for 45% of all cultivated land in the Southeast. Corn
6-8
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Chapter 6
Table 6-1. Annual Revenues by State for Various Crops.
Value
Crop ($1,000)
Corn for Grain
Alabama 56,550
Florida 31,493
Georgia 203,931
Mississippi 22,600
North Carolina 324,789
South Carolina 104,333
Tennessee 193,687
Cotton
Alabama 145,540
Florida 8,112
Georgia 97,325
Mississippi 449,630
North.Carolina 30,944
Tennessee . 109,610
Sugarcane for sugar and seed
Florida 369,899
Tobacco
Florida NA
Georgia NA
North Carolina NA
South Carolina NA
Tennessee NA
Peanuts for Nuts
Alabama 133,930
Florida 48,600
Georgia 472,645
North Carolina 122,941
South Carolina 5,882
Soybeans
Alabama 140,719
Florida 31,036
Georgia 179,676
Mississippi 365,018
North Carolina 196,673
South Carolina 125,214
Tennessee 230,373
Source: U.S. Department of Agriculture, Agricultural Statistics:
1987. pp. 32, 34, 62, 63, 80, 93, 121, 126, 127.
-------
Southeast
continues to account for 5% of southeastern agriculture (Bureau
of the Census, 1982). Table 6-1 compares annual revenues by
state for various crops.
Forests
The commercial viability of southeastern forests has
increased greatly since World War II, primarily due to the
increased use of softwoods, such as pines and firs for plywood
and uses that once required hardwood. Because this transition
coincided with lower farm prices and declining soils in the
piedmont foothills of the Southeast, many mountain farms have
been converted to forests. Conversely, in the last 10 years, 7
million acres of coastal plain forests have been converted to
agriculture (Healy, 1985) .
Approximately 45% of the nation's softwood (mostly loblolly
pine) and 50% of its hardwood are grown in the region. Forests
cover 60% of the Southeast, and 90% of forests are logged.
Oak-hickory covers 35%, and pine covers another 33% of commercial
forests. Only 9% of the southeastern forests are owned by the
Federal and state governments, and 18% are owned by the forest
industry. In contrast, 73% of the forests are owned by farmers
and other private parties (Healy, 1985).
Indoor and Outdoor Comfort
The Southeast is one of the few areas that spends as much
money on air-conditioning as on heating. Figure 6-2 shows
temperatures throughout the Southeast for the months of January,
April, July, and October. Even in January, about half the region
experiences average temperatures above 50°F, and almost the
entire region has a typical daily high above 50°F. Thus, with
the possible exception of the mountains of Tennessee and North
Carolina, a global warming would increase the number of days
during which outdoor temperatures would be unpleasantly warm.
PREVIOUS STUDIES OF THE IMPACTS OF CLIMATE CHANGE ON THE
SOUTHEAST
Most studies examining the impact of global warming on the
Southeast have focused on sea level rise. Recent efforts have
addressed other topics.
Flooding
Leatherman (1984) and Kana (1984) applied flood-forecasting
models to assess the potential increases in flooding in
Galveston, Texas, and Charleston, South Carolina. For the
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LU
QC
P
LU
0.7
o.e
0.5
0.4
0.3
0.2
0.1
-0.1
-0.2
-0.3
-0 4
WMv
Spring
(a)
1
I
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ass
QFDL
OSU
Annurt
(b)
Wtitar
Spring
Sunnar
Fal
Annual
Figure 6-2.
Climate scenarios for the Southeast, (a)
temperature and (b) precipitation.
6-11
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Southeast
Galveston area, a 90-cm rise would increase the 100-year
floodplain by 50%, while a 160-cm rise would enable the 100-year
strom to overtop the seawall erected after the disaster of 1900.
For the Charleston area, a 160-cm rise would increase the 10-year
floodplain to the area currently covered by the 100-year
floodplain.
Gibbs (1984) estimated that the economic impact of a 90-cm
rise by 2075 could be as great as $500 million for Galveston and
over $1 billion for Charleston. However, he also estimated that
the adverse impacts of flooding and land loss could be cut in
half if the communities adopted measures in anticipation of sea
level rise. Titus (1984) focused on decisions facing Sullivans
Island, South Carolina, in the aftermath of a storm. He
concluded that rebuilding $15 million in oceanfront houses after
a storm would not be economically sound if future sea level rise
is anticipated, unless the community is prepared to continuously
nourish its beaches.
Wetlands
Kana et al. (1986) surveyed marsh transects and estimated
that 90- and 160-cm (3.0- and 5.2-foot) rises in sea level would
drown 50 and 90%, respectively of the marsh around Charleston,
South Carolina. Armentano et al. (1988) estimated the Southeast
would lose 35 and 70% of its coastal wetlands for respective
rises of 1.4 and 2.1 m, assuming that developed areas are not
protected.
Infrastructure
The Louisiana Wetland Protection Panel (1987) concluded that
a rise in sea level might necessitate substantial changes in the
ports and shipping lanes of the Mississippi River to prevent the
loss of several thousand square miles of coastal wetlands. Titus
et al. (1987) showed that a reconstructed coastal drainage system
in Charleston should be designed for a 1-foot rise in sea level
if the probability of such a rise is greater than 30%. Linder et
al. (1988) found that warmer temperatures would require an
electric utility company to substantially increase its generating
capacity.
Several dozen researchers presented papers on other global
warming impacts on the Southeast at a 1987 EPA conference held in
New Orleans (Meo, 1987). The proceedings include papers on
forests, agriculture, coastal erosion, and water resources.
6-12
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Chapter 6
CLIMATE CHANGE STUDIES IN THIS REPORT
Table 6-2 and Figure 6-3 illustrate the studies undertaken
as part of this effort. Models of coastal erosion, coastal
wetland loss, agricultural yields, and electricity consumption
were used to derive regionwide estimates. Efforts to estimate
impacts on water resources, infrastructure, forests, and the
ecology were limited to conducting illustrative case studies.
SCENARIOS OF FUTURE CLIMATE CHANGE
Figure 6-2 illustrates the scenarios of future climate
change from general circulation models. Table 6-3 shows the more
detailed seasonal changes.
Table 6-3 illustrates how the frequency of mild days during
the winter and the frequency of very hot days during the summer
might change under the Goddard Institute for Space Studies (GISS)
doubled C02 scenario. These estimates used average monthly
changes in temperature and assumed no change in the frequency or
duration of temperature extremes. Under this scenario, the
number of days per year in which the mercury would fall below
freezing would decrease from 34 to 6 in Jackson, Mississippi;
from 39 to 20 in Atlanta; and from 41 to 8 in Memphis. The
number of winter days above 70°F would increase
from 15 to 44 in Jackson, from 4 to 14 in Atlanta, and from 5 to
24 in Memphis.
Of the nine cities shown, only Nashville has summer
temperatures that currently do not regularly exceed 80 °F.
However, the number of days with highs below 80°F would decline
from 60 to 34. Elsewhere, the heat would be worse. The number
of days per year above 90°F would increase from 30 to 84 in
Miami, from 17 to 53 in Atlanta, and from 55 to 85 in New
Orleans. Memphis, Jackson, New Orleans, and Jacksonville, which
currently experience 0 to 3 days per year above 100°F, would have
13-20 such days (Kalkstein, Vol. _).
Coastal Impacts
A number of national studies for the report presented
results for the effects of climate change on the southeastern
coast. Leatherman estimated the cost of maintaining recreational
beaches. Park et al. and Weggel et al. examined the impacts
onwetland loss and shoreline defense, and used their results to
estimate the regionwide cost of raising barrier islands.
6-13
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Southeast
Table 6-2. Studies of the Southeast
Regional Studies
o Impacts on Runoff in the Upper Chattaboochee River
Basin Hains, C.F. Haines, Hydrologist, Inc.
o Projected Changes in Estuarine Conditions Based on
Models of Loncr-Term Atmospheric Alteration
Livingston, Florida State University.
o Policy Implications of Global Climatic Change Impacts
upon the Tennessee Valley Authority Reservoir System,
Apalachicola River. Estuary. and Bay and South Florida
Meo, Ballard, Deyle, James, Malysa, and Wilson,
University of Oklahoma.
o Potential Impacts on Climatic Change on the Tennessee
Valley Authority Reservoir System Miller and Brock,
Tennessee Valley Authority.
o Impact of Climate Change on Crop Yield in the
Southeastern U.S.A. Peart, Jones, and Curry,
University of Florida.
o Methods for Evaluating the Potential Impacts of Global
Climate Change Sheer and Randall, Water Resources
Management, Inc.
o Forest Response to Climate Change; A Simulation Study
for Southeastern Forests Urban and Shugart,
University of Virginia.
National Studies that Included Southeast Results
o The Economic Effects of Climate Change on U.S.
Agriculture; A Preliminary Assessment. Adams,
Glyer, and McCarl, Oregon State University.
o National Assessment of Beach Nourishment Requirements
Associated with Accelerated Sea Level Rise --
Leatherman, University of Maryland.
o The Potential Impacts of Climate Change on Electric
Utilities; Regional and National Estimates Linder
and Inglis, ICF Inc.
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Chapter 6
The Effects of Sea Level Rise on U.S. Coastal Wetlands
Park and Trehau, Butler University.
Potential Effects of Climatic Change on Plant-Pest
Interactions Stinner, Rodenhouse, Taylor, Hammond,
Purrington, McCartney, and Barrett, Ohio Agricultural
Research and Development Center.
An Overview of the Nationwide Impacts of Rising Sea
Level Titus and Greene, U.S. Environmental
Protection Agency.
The Cost of Defending Developed Shorelines Along
Sheltered Waters of the United States from a Two Meter
Rise in Mean Sea Level Weggel, Brown, Escajadillo,
Breen, and Doheny, Drexel University.
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Chapter 6
Table 6-3. The GISS Doubled C02 Scenario: Frequency of Hot and Cold Days (°F)
Number of Winter days with... Number of Summer days with
Daily Low <32 Daily High >= 70 Daily High <80 Daily High >90 Daily High >= 100
YEAR
HIST 2xC02 HIST 2xC02 HIST 2xC02 HIST 2xC02 HIST 2xC02
Atlanta,
Birmingham,
Charlotte,
Jackson,
Jacksonville,
Memphis,
Miami,
Nashville,
New Orleans,
GA
AL
NC
MS
FL
TN
FL
TN
LA
38.3
35.5
42.1
33.5
9.3
41.2
0.2
42.5
14.9
20.5
8.1
23.8
5.9
1.7
8.1
0.0
15.4
3.5
4.2
7.1
3.4
15.3
34.6
5.2
72.9
0.3
24.9
13.6
30.7
9.9
43.5
49.6
23.6
82.7
8.6
39.5
10.0
4.5
11.9
0.8
2.3
4.9
0.6
60.4
0.9
2.2
0.4
3.7
0.2
0.3
0.7
0.0
33.7
0.1
17.1
34.1
23.1
55.1
46.4
50.5
29.8
10.5
55.4
53.3
72.5
56.5
83.1
81.3
74.8
83.5
20.2
84.9
0.6
1.5
0.1
2.0
0.6
2.6
0.0
0.3
0.3
4.2
10.7
5.9
19.5
14.1
19.1
2.5
3.5
13.5
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Southeast
The projected rise in sea level would cause shorelines to
retreat, exacerbate coastal flooding, and increase the salinity
of estuaries, wetlands, and aquifers. The nationwide study of
sea level rise focused on retreating shorelines and the costs of
holding back the sea. (See Chapter 9 for a discussion of the
rationale, methods, and nationwide results of these studies.)
Coastal Wetlands
Park (Volume ) examined 29 southeastern sites to estimate
the likely regionwide loss of coastal wetlands for a variety of
scenarios of future sea level rise. His analyses included such
societal responses as providing structural protection for all
shorelines (total protection), protecting areas that are densely
developed today (standard protection), and allowing shorelines to
adjust naturally without coastal protection (no protection).
Figure 6-4 illustrates Parks's projections for the year 2100
for the various scenarios of sea level rise and coastal defense.
Even if current sea level trends continue, 25% of the Southeast's
coastal wetlands will be lost, mostly in Louisiana.
o current trends imply a loss of 15%;
o a 50-cm rise would result in a loss of 35 to 50%;
depending on how shorelines are managed;
o a 100-cm rise results in losses of 45 to 68%; and
o a 200-cm rise implies losses of 63 to 80%.
Park et.al. estimate losses of 50, 75, and 98% for Louisiana
under the three scenarios. However, Park did not consider the
potential for mitigating the loss by restoring the flow of river
water into these wetlands. Titus and Greene estimated
statistical confidence intervals illustrated in Table 6-4.
Total Coastal Land Loss
Park also estimated total land loss, including both wetlands
and dry land. Most of the land loss from a rise in sea level
would occur in Louisiana, as shown in Table 6-4. A 50-cm (20-
inch) sea level rise would result in the loss of 1900-5900 mi2 of
land, while a 200-cm rise would inundate 10000-11000 mi2.
Cost of Protecting Recreational Beaches
In Volume , Leatherman notes that the projected rise in
sea level would threaten all developed recreational beaches.
Even a 1-foot sea level rise would erode shorelines over 100 feet
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A. NO PROTECTION
0.0 0.1 0.3 0.6 1.0 1.5 2.2 3.0
SEA LEVEL
B. STANDARD PROTECTION
0.0 0.1 0.3 0.6 1.0 1.5 2.2 3.0
SEA LEVEL
C. TOTAL PROTECTION
0.0 0.1 0.3 0.6 1.0 1.5 2.2 3.0
SEA LEVEL
SWAMP
FRESH MARSH
MANGROVE
BEACH/FLAT
SALT MARSH
SWAMP
FRESH MARSH
vxwxmn
MANGROVE
BEACH/FUAT
SALT MARSH
SWAMP
FRESH MARSH
MANGROVE
BEACH/FLAT
SALT MARSH
Figure 6-4. Southeastern Wetland Loss for Three Shoreline
Protection Options
Source: Park et al., Volume _.
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Southeast
Table 6-4. Summary of Southeastern Results ($ billions)
50
100
200
If Developed Areas Are Protected
Land Lost
Dryland Lost (sq. mi)
Wetlands Lost (%)
Cost of Coastal Defense
Open Coast
Sand
Elevated Structures
Sheltered Shores
If All Shores Are Protected
Land Lost
Drylands Lost (sq. mi)
Wetlands Lost (%)
If No Shores Are Protected
Land Lost
Dryland-Lost (sq. mi)
Wetlands Lost (%)
1900-5500
24-50
19-28
10-15
5-9
2-5
0
38-61
2300-5900
22-48
2600-6900
34-77
42-75
19-30
10-40
5-13
0
47-90
3200-7600
30-75
4200-10100
40-90
127-174
44-74
60-75
9-41
0
68-93
4800-10800
37-88
Source: Titus and Greene
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Chapter 6
throughout the Southeast. Along the coasts of North Carolina and
Louisiana, the erosion would be considerably greater. (See
Chapter 9 for a discussion of methods for estimating coastal
erosion.) Because the distance from the high tide line to the
first building is rarely more than 100 feet, most recreational
beaches would be lost, unless either the buildings were removed
or engineering measures were undertaken.
Table 6-4 illustrates Leatherman's estimates of the cost of
protecting recreational beaches by pumping sand from offshore
locations (see Chapter 9, Sea Level Rise for state by state
results). A 1-m rise in sea level would imply almost $20
billion in dredging costs, with Texas spending $8.5 billion and
Florida and Louisiana each spending over $3 billion.
Using constant unit costs (except for Florida), Leatherman
estimated that a 2-m rise would only double the total cost to $43
billion. Titus and Greene estimated that if the unit costs of
sand increased, 1- and 2-m rises would cost $30 and 74 billion,
respectively. They also estimated that the cost of rebuilding
roads and utilities on barrier islands would be 5-9, 10-40, and
60-75 billion for the three scenarios.
Cost of Protecting Calm-Water Shorelines
While Leatherman focused only on the open ocean coast,
Weggel et al. estimated the regionwide costs of holding back the
sea in developed sheltered and calm-water areas. Table 6-4
illustrates the estimated costs for the Southeast. Weggel et al.
estimate that about $2 billion would be spent to raise roads and
to move structures, and $23 billion would be spent to erect the
necessary levees and bulkheads. The combined cost is $68-83
billion. These estimates do not include the costs of preventing
flooding or of protecting water supplies.
Tennessee Valley Authority Studies
The Tennessee Valley Authority (TVA) was created in 1933 to
spur economic growth in an area previously considered to be one
of the nation's poorest. Geographically isolated by the
Appalachian Mountains, the region lacked electricity and roads,
and the Tennessee River could not provide reliable transportation
because it flooded in the spring and dried to a trickle during
the summer. By creating the TVA, Congress sought to remedy this
situation by harnessing the river to provide electricity, to
prevent the flooding that had plagued Chattanooga, and to ensure
sufficiently stable riverflows that would permit maintenance of a
9-foot-deep navigation channel.
6-21
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Southeast
The region administered by the TVA covers 40,000 mi2 and
includes parts of seven states. In the last half century, the
TVA has coordinated the construction of 43 major dams along the
river and its tributaries, many of which are shown in Figure 6-5.
The system provides power to over 7 million people, and contains
675 miles of navigable waterways with annual commercial freight
of 28 million tons. The lakes created by the dams have over
10,000 miles of shoreline, which generate 75 million visits each
year and along which people have invested $630 million. The
lakes and streams generate 17 million visits per year, enough to
indirectly boost the region's annual economy by $400 million
(Miller and Brock).
To assess the potential impacts of climate change, Miller
and Brock conducted a modeling study of the water resource
implications, and Meo et al. examined the policy implications for
the TVA.
TVA Modeling Study
Methods
Miller and Brock used the TVA's "Weekly Scheduling Model,"
on which the Agency currently bases its operations, to assess the
impacts of climate change. This is a linear programming model
that selects a weekly schedule for managing each reservoir in the
TVA system by seguentially satisfying the objectives of flood
control, navigation, water supply, power generation, water
quality, and recreation. Miller and Brock used this model to
simulate reservoir levels, riverflows, and hydropower generation
for wet and dry scenarios, Abased on the runoff estimates from the
GISS doubled C02 model run.*
Miller and Brock assessed the potential impacts of climate
change on flood levels in Chattanooga, Tennessee, using a model
that had been developed to estimate the constraints on weekly
tributary releases. They also estimated the potential
implications for water quality in the Upper Holston Basin of the
valley, using a reservoir water quality model, a riverflow model,
and a water quality model that TVA has used in the past to
determine the environmental constraints affecting riverflow.
*
TVA used runoff from the GCMs, rather than hydrologic
analysis, to estimate streamflow. The GISS scenario estimates high
runoff. Since the Geophysical Fluid Dynamics Laboratory (GFDCL)
and Oregon State University (OSU) scenarios estimated that no
runoff the lxC02 and 2xCO2 runs, Miller and Brock used the inverse
of GISS as a dry scenario (Rind, 1988)).
6-22
-------
LEGEND:
TVA POWER SERVICE AREA
- TENNESSEE RIVER WATERSHED
Figure 6-5. (a) Map of the TVA region and (b) schematic of the
TVA reservoir system (b).
Source: Tennessee Valley Authority
6-23
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Southeast
Limitations
Since the riverflow scenarios were not based on hydrologic
analysis, conclusions cannot be drawn regarding the sensitivity
of riverflow to climate change. A key limitation for the flood
analysis was EPA's assumption that every storm in a given month
would result in a change in riverflow proportional to the change
in monthly runoff. (See Chapter 3 on climate scenarios.)
Finally, the study assumed that TVA did not mitigate impacts by
changing its operating rules for the reservoirs in response to
climate change. Changes in operating rules may mitigate some
impacts.
Results
Reservoir levels. Assuming TVA's current operating rules,
Miller estimated reservoir levels resulting from the scenarios,
with levels for the Norris reservoir shown in Figure 6-6.
Reservoir levels are generally higher in the wet scenario and
lower in the dry. Currently, water levels are above 1,010 feet
(NLVD) from early May to early August in a typical year. Under
the wet scenario, the water would be above this level from early
April to early September in a typical year; during the (1%)
driest years, the water levels would be similar to the current
normal level between May and October. In the dry scenario, water
levels would never exceed 1,005 feet in a typical year and even
during the (1%) wettest years they would barely exceed the
current normal condition between April and September.
These projected lake levels have important implications for
recreation in the Tennessee Valley, which is supported by
facilities worth over $600 million. Even today, recreation
proponents are concerned with reservoir levels dropping during
some summers. Miller and Brock found that the wet scenario would
largely eliminate current problems with low lake levels; in
contrast, the dry scenario would make these problems the norm.
Water Quality. Miller and Brock found that a dryer climate
could also create environmental problems. Lower flows would
reduce the dilution of municipal and industrial effluents
discharged into the river and its tributaries. Moreover, because
water would generally remain at the bottom of reservoirs for a
longer period of time, the amount of dissolved oxygen would
decline; this would directly harm fish and reduce the ability of
streams to assimilate wastes. Miller and Brock concluded that
the water supplies from TVA probably would be sufficient, but the
TVA could experience operational difficulties and customer
dissatisfaction due to degraded water quality. During extended
low-flow conditions, wastes would have increased opportunities to
backflow upstream to water supply intakes.
6-24
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Flooding. Although a dryer climate would exacerbate many
current problems facing TVA, a wetter climate could create
problems, particularly the risk of flooding, in areas that are
currently under control. Miller and Brock found that in the wet
scenario, during exceptionally wet years, storage was inadequate
at the tributary reservoirs; this condition could result in
uncontrolled spillage over dams. A high probability of flooding
would also exist at Chattanooga. Miller and Brock took the
levels of the five worst floods of the last 50 years at
Chattanooga that did not overflow the banks of the Tennessee
River and flood the city, and they compared these floods with
floods that would result under the wet GISS scenario.Under the
GISS scenario, two of the five floods would overtop the banks.
The worst flood would reach a level of 56.3 feet and would cause
over $1 billion in damages. (See Figure 6-7.) The second worst
flood would reach a level of 46 feet, causing over $200 million
in damages.
Flooding could be reduced if climate change were
incorporated into operating rules that, kept water levels lower
in reservoirs on tributaries (although this would diminish the
hydropower benefits from a wetter climate). However, changes in
operating rules would not be sufficient to protect Chattanooga
from a repeat of the worst storm in which rainfall was largely
concentrated over the "mainstem" reservoirs, which do not have
substantial flood- control storage.
Power Generation. Miller and Brock calculated that the wet
and dry scenarios imply, respectively, an annual increase of 3.2
megawatt-hours (16%, $54 million/year) and a decrease of 4.6
megawatt-hours (24%, $87 million/year), given current capacity
and operating rules.
Climate change could also have an impact on fossil-fuel
powerplants. If river temperatures become warmer, additional
dilution water would be required for powerplants. The water may
be available if the climate becomes wetter, but under the dry
scenario, meeting minimum flow requirements would be more
difficult. Miller suggested that the most feasible operational
change would be to cut back power generation at fossil/fuel
powerplants during periods of low flow. However, hydropower
production would also be reduced during periods of low flow, so
cutting back production might not be acceptable. One alternative
would be for the plant to construct cooling towers, which would
eliminate discharges of hot water, at a capital cost of
approximately $75 million.
6-26
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Chapter 6
Figure 6-7. Chattanooga was vulnerable to flooding until the TVA
system of dams was constructed. The upper photo
shows the 1867 Flood, with levels similar to what
Miller and Bruck project could happen under the wet
scenario.
Source: Tennessee Valley Authority
6-27
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Southeast
Tennessee Valley Policy Study
Meo et al. analyzed the history, statutory authority, and
institutional structure of the TVA to assess the ability of the
organization to respond to climate change. Their analysis relied
both on the available literature and on interviews with a few
dozen officials of TVA and states within the region.
Meo et al. divided the possible responses of TVA into two
broad categories: (1) continuing the current policy of
maximizing the value of hydroelectric power, subject to the
constraints of flood control and navigation; and (2) modifying
priorities so that power generation would be subordinated to
other objectives if doing so would yield a greater benefit to the
region.Meo concluded that if the climate becomes wetter, current
policies would probably be adequate to address climate change
because the only adverse effect would be the risk of additional
flooding, which is already a top priority of the system.
If climate becomes drier, on the other hand, existing
policies might be inadequate, because they require power
generation to take precedence over many of the resources that
would be hardest hit. Although they expect that the TVA will be
more successful at addressing the current (1988) drought, Meo et
al. found that during the 1985-86 drought, falling lake levels
impaired recreation and reduced hydropower generation, forcing
the region to import power while five powerplants sat idle.
Meo et al. point out that groundwater tables are falling in
parts of the region, in part because numerous tributaries
recharge the aquifers whenever water is flowing but are allowed
to run dry when water is not being released for hydropower. Meo
et al. suggest that the deteriorating groundwater quality and
availability are likely to lead a number of communities to shift
to surface water supplies in the coming decades, adding another
use that must compete for the water that is left over when the
demands for power have been met. Even with current climate these
contend, the TVA should assess whether other uses of the region's
water resources would benefit the economy more. If climate
became drier, the need for such a reevaluation would be even more
necessary.
Studies of Effects on Lake Lanier and Apalachicola Bay
Figure 6-8 shows the boundaries of the Chattahoochee-Flint-
Apalachicola River Basin, which encompasses 19,800 mi2. The
Corps of Engineers and others who manage the Chattahoochee River
as it passes through Lake Lanier on its way to the Apalachicola
estuary and the Gulf of Mexico face many of the same issues as
those faced by the TVA. However, they also are managing the
6-28
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Chapter 6
water supply of Atlanta, the 2nd largest city in the Southeast,
and the flow of water into an estuary that supports the most
productive fishery in Florida. (Statistical Abstract of U.S.:
1988, Department of Commerce.)
A number of researchers were involved in EPA's assessment of
the potential implications of climate change for this watershed.
A study of Lake Lanier and a study of the implications for the
fish in Apalachicola Bay are discussed in the following sections
of this chapter.
Lake Lanier
Lake Lanier, located 30 miles northeast of Atlanta, is a
source of water for the city and nearby jurisdictions. Federal
statutes require the U.S. Army Corps of Engineers to manage Lake
Lanier to provide flood control, navigation, and hydropower. The
lake is also managed to mind nonstatutory objections such as
recreation, minimum flows for environmental dilution, and water
supply.
Since Lake Lanier was dammed in 1957, the statutory
objectives of flooding and navigation have been met; historical
annual hydropower generation has been 199. 134 MWH1, equal to 2%
of today's power requirements for Atlanta ; and the releases of
water have fulfilled the additional minimum flow needed to dilute
the effluents from sewage treatment plants.
During the last two decades, the lake's shoreline has been
substantially developed with marinas, houses, and hotels. To a
large degree, the residents have become accustomed to the higher
water levels that have prevailed from the 1970s through 1984.
Droughts from 1985 to the present, however, have lowered
lake levels, disrupting recreation. In the summer of 1986,
navigation for recreational boats located downstream of the lake
was curtailed due to minimal releases from the lake. Recently,
Atlanta imposed water-use restrictions, with the objective of
cutting consumption 10-20%. A bill has been introduced to add
recreation to the list of statutory purposes (HR-4257). [Rep.
Jenkins, Rep. Barnard, Rep. Darden. HR-4254 "Georgia Reservoir
Management Improvement Act of 1988," 100th Congress, 20 Session].
Runoff in the Chattahoochee River Basin
To assess the potential implications of climate change for
Lake Lanier, Haines estimated the flows of water into the lake.
6-29
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Southeast
Study Design. Haines calibrated the Sacramento hydrology
model developed by the National Weather Service (Burnash, 1973)
to the conditions found in the watershed of the upper
Chattahoochee River. He then generated scenarios of riverflow
for the baseline climate and the three doubled CO2 scenarios.
Limitations. The Sacramento model was designed primarily
for flood forecasting, not base flow. In addition, the model was
calibrated using the data on evaporation of water from pans,
which is not perfectly correlated with evapotranspiration.
Results. As with the Tennessee River, the major climate
models disagree on whether the Chattahoochee watershed would
become wetter or dryer with an effective doubling of greenhouse
gases. Haines estimated that the wetter GISS model would
increase the average annual riverflow of the Chattahoochee River
by 13%, while the drier OSU and GFDL models imply declines of 19
and 27%, respectively, as shown in Figure 6-9. The GISS scenario
implies slight decreases in winter flow and increases the rest of
the year. The GFDL scenario shows substantial decreases
throughout the year, with almost no flow in late summer. The OSU
scenario also shows reductions, but the reduction is greatest
during the flood season (February to May) and negligible during
the dry season (late summer/early fall).
Management of Lake Lanier
Sheer used the calculation of riverflow from Haines to
estimate the management implications of climate change.
Study Design. Sheer modified a monthly water balance
model/operations model previously applied in Southern California
for the lake, based on current operating rules for the reservoir.
For the first set of runs, the model assumes that (1) minimum
flows are maintained for navigation and environmental dilution at
all times, (2) lake levels are kept low enough to prevent
flooding, (3) historic rates of consumption continue, and (4)
peak hydropower generation is maximized. To ensure that the
assumptions adequately reflect the actual decision rules used by
water managers, Sheer reviewed the rules with local officials
from the Corps of Engineers, the Atlanta Regional Council, and
others responsible for managing the water supply. In a second
set of runs, Sheer examined the impacts of climate change under
alternative operating rules that assume recreation is also a
statutory objective.
Limitations. The Sheer model does not consider changes in
demand for water due to climate change. In addition, model
results were not compared to actual historic lake levels.
6-30
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APALACHICOLA RIVER'
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Figure 6-8.
Drainage area of the Apalachicola-Chattahoochee-
Flint River system.
6-31
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Results. Figures 6-10 shows Sheer's estimates of lake
levels. Figure 6-11 shows quarterly hydropower production.
Under the wet GISS scenario, annual power production would
increase by 9%. The higher streamflows in this scenario would
still be well below those that occasionally occurred before Lake
Lanier was closed; hence, no significant threat of flooding would
exist for a repeat of the climate of 1951-80. Under the dry GFDL
scenario, however, power production would drop 47%, and lake
levels would be likely to drop enough to substantially disrupt
recreation. This scenario assumes that Atlanta would continue to
take as much water as it does currently (a conservative
assumption given the area's rapid growth).
Sheer also examined the implications of making recreation a
statutory objective. Although, it would be possible to maintain
lake levels, even in the dry GFDL scenario. Altanta's water
supply would be threatened. With the current climate, strict
enforcement of such a policy would result in Lake Lanker.
Although the wet GISS scenario would reduce this to 1 month
every30 years, under the dry GFDL scenario, Atlanta would have to
use an alternative source of water one to three months each
summer.
Implications. Climate change combined with population
growth may require water managers to reexamine the tradeoffs
between the various uses of the Chattahoochee River and Lake
Lanier. A number of local water officials who met with Sheer
suggested that an appropriate response to changing water
availability might be to relax minimum flow requirements for
navigation and environmental quality. They reasoned that minimum
flows for environmental purposes are based on conditions that
prevail only when sewage treatment plants are at their maximum
discharge and temperatures are high, and that little is
accomplished by maintaining minimum flows for navigation because
ship traffic is light in the lower Chattahoochee. Others argued,
however, that it would be unwise to assume that minimum flows
could be decreased because future growth may increase the need
for dilution of effluents, and warmer temperatures would speed
biological activity. The likely impacts of climate change on
Apalachicola Bay may also increase the need to maintain minimum
flows.
Apalachicola Bay. Florida
Apalachicola Bay supports hundreds of commercial fishermen;
over 80% of Franklin County earns a livelihood from the bay (Meo,
Vol. _). The contribution of fishing to the area was estimated
at $20 million for 1980, representing 90% of Florida's oyster
harvest and 10% of its shrimp harvest. This figure is projected
to grow to $30-60 million by 2000.
6-33
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Although the state has purchased most of the land that is
not part of a commercial forest, economic pressures on forestry
companies to sell land for coastal development are increasing.
In 1979, the Apalachicola National Estuarine Sanctuary was
created by the National Oceanic and Atmospheric Administration to
prevent development from encroaching into this relatively
pristine estuarine environment.
The biology of the Apalachicola Bay estuary may be affected
by higher temperatures, higher sea levels, and different flows of
water into the Apalachicola River. Haines estimated the flow of
the Apalachicola River, and Park estimated wetland loss due to
sea level rise. Livingston used both of these results and the
temperature change scenarios to evaluate the potential impacts on
the bay's fish populations.
Sea Level Rise
Park's methods for estimating wetland loss are described in
chapter 9: Sea Level Rise. He estimated that a 1-m rise in sea
level would inundate approximately 60% of the salt marshes in
Apalachicola Bay, and that mangrove swamps, which are rarely
found outside southern Florida at present, would replace the
remaining salt marsh. Table 6-6 illustrates Park's estimates of
wetland shifts due to sea level rise.
Apalachicola River Flow
Study Design. Haines estimated the impact of climate change
on riverflow, using a regression model, which is simpler than the
Sacramento model he used for the Chattahoochee River analysis.
The regression expressed the logarithm of riverflow as a function
of the logarithms of precipitation and evapotranspiration for a
few weather stations located in the basin.
Limitations. Haines' procedure greatly oversimplified the
relationships between the causal variables and riverflow,
ignoring the impacts of reservoir releases and the failure of the
relationships to fit the simple log-linear form. These results
should be interpreted as an indication of the potential direction
of change.
Results. Figure 6-12 illustrates Haines' estimates of
average monthly flows for the Apalachicola estuary. Annual
riverflow would decrease under all scenarios, although it would
increase in the summer and fall for the GISS and OSU scenarios,
respectively.
6-36
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Chapter 6
Table 6-6. Loss of Coastal Wetlands in Apalochicola Bay
(hectares)
Swamps
Fresh Marsh
High Marsh
Low Marsh
Mangrove
Wetlands
1987
9.46
1.46
1.19
3.42
0
Baseline
6.71
1.27
0.37
2.33
0
50
6.26
1.17
0.035
0.388
3.057
100
5.47
1.00
0.035
0.062
2.13
200
4.16
0.25
0.020
0.032
1.80
Source: Park
6-37
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Chapter 6
Fish Populations in Apalachicola Bay
Study Design. Using data from the literature on the
tolerance of various species to warmer temperatures, Livingston
estimated the number of months in a typical 30-year period during
which the estuary would be too hot for these species and
extrapolated this information to estimate reductions in
populations.
Hydrologic modeling was not used to estimate the combined
impacts of sea level rise and changing riverflow on salinity.
Since Raines estimated that riverflow would be lower under all
three scenarios, salinity in Apalachicola Bay would increase.
Recent droughts have decreased riverflow by approximately the
same magnitude as would be suggested by the dry OSU and GFDL
scenarios. Livingston used historic data to estimate regression
equations relating riverflow to salinity and salinity to
populations of some commercially important seafood species.
Limitations. There is no historical record by which to
estimate the impact of warmer temperatures on the Apalachicola
(or any other) estuary. Livingston did not model the
relationships between various aquatic species or how they would
change. He did not consider how finfish and shellfish might
adapt to climate change, and he was unable to estimate the impact
of wetland loss on populations of finfish and shellfish.
The limitations in Haines1 estimates of riverflow do not
significantly affect the results of Livingston's study because
riverflow was one of several variables to be considered. The
uncertainties surrounding changes in rainfall probably dwarf any
errors due to Haines1 simplified hydrology, and higher
temperatures and sea level rise appeared to be more important.
Results. The results of this study suggest a dramatic
transformation of the estuary from subtropical to tropical
conditions.
Warmer temperatures. Livingston concluded that warmer
temperatures would have a profound effect on seafood species in
the estuary because they cannot tolerate temperatures much above
those that currently prevail. Figure 6-15 compares the number of
months in a six-year period (based on 1971-76) in which
temperatures exceed a particular level for the current climate
and the GISS, GFDL, and OSU scenarios, with known thresholds for
major commercial species.
6-39
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Southeast
Livingston concluded that crabs, shrimp, oysters, and
flounder could not survive in the estuary with the warming
projected by the GISS and GFDL scenarios, which imply close to
100% mortality for blue crab larvae and juveniles. The GFDL
scenario would also imply over 90% mortality for spotted sea
trout, oyster larvae, panfish, and flounder. The mortality under
the milder GISS scenario would be only 60%.
Although Livingston concludes that the oysters would
probably be eliminated, he cautions that shrimp and other mobile
species might adapt by fleeing the estuary for cooler gulf waters
during the summer. However, such a flight would leave them
vulnerable to predators.
Increased Salinity. Although it appears that sea level rise
and warmer temperatures are likely to substantially reduce the
productivity of the estuary, the probable impact of precipitation
changes is less clear. However, lower flow in the Chattahoochee
would combine with sea level rise to increase salinity
concentrations in the estuary. Livingston concluded that oysters
appear to be the most vulnerable to increases in salinity because
oyster drill and other predators, as well as the disease MSX,
generally require high salinities. Livingston estimated losses
of 10 to 35% for oysters, blue crabs, finfish, and white shrimp
under the GFDL scenario due to salinity increases alone.
Sea Level Rise. Livingston also concludes that the loss of
wetland acreage would have important impacts on the estuary.
Table 6-7 also includes Livingston's estimates of losses in
particulate organic carbon, the basic source of food for fish in
the estuary. Sea level rise between 50 and 200 cm would reduce
available food by 42 to 78%. A proportionate loss in seafood
populations would not necessarily occur, since organic carbon
food supplies are not currently the constraining factor for
estuarine populations. However, wetlands also are important to
larvae and small shrimp, crabs, and other species, serving as a
refuge from predators. A rise in sea level of a meter or more
could lead to a major loss of fisheries.
Despite the adverse impacts on shellfish and flounder, a
number of species might benefit from global warming. For
example, Livingston concludes that pink shrimp could become more
prevalent. Moreover, some finfish spend their winters in
Apalachicola Bay and occasionally find the estuary too cold.
Other species, such as rock lobster, that generally find the
waters too cold at present also may be found in the estuary in
the future.
6-40
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Table 6-7. Projected Changes of the Net Input of Organic Carbon
(mtons/year) to the Apalachicola Bay System for Various
Scenarios of Sea Level Rise
Factor
Current Scenario
for 2100
Baseline
Sea Level Rise
0.5 M Rise
1.0 M Rise
2.0 M Rise
Fresh Sea- Salt Phyto-
Wetlands Grass Marshes Plankton Total
30,000 27,200 46,905 233,280 337,385
26,100 28,700 23,500 144,640 222,940
24,000 28,800 4,690 71,450 128,940
21,300 30,100 940 58,790 111,130
4,980 31,035 780 15,160 51,955
Source: Livingston, Volume .
6-42
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Chapter 6
Implications. Based on Livingston's projections, Meo et al.
(Volume ) used current retail prices of fish to estimate that
the annual net economic loss to Franklin County would be $5-15
million under the GFDL scenario, $1-4 million under GISS, and $4-
12 million under the OSU scenario.
Livingston's results should not be interpreted to mean that
fishing will be eliminated from Apalachicola Bay. The extent to
which commercially viable tropical species could replace the
species that are lost simply cannot be estimated at this time.
Agriculture
Agriculture in the Southeast will be directly affected by
changes in climate and indirectly affected by changes in economic
conditions and pests. This section presents results from a crop
modeling study of yield changes by Peart et al., and regional
results from national studies of agricultural production shifts
by Adams et al. and of impacts of changes in pest populations by
Stinner et al.
Crop Modeling Study
Study Design
Peart et al. used the crop models CERES-Maize (Jones and Kiniry,
1986) and SOYGRO (Wilkerson et al., 1985) to estimate the impacts of
climate change on yields of corn and soybeans for 19 sites throughout
the Southeast and adjacent states. These models have been used for
several years by agricultural scientists to project the impacts .of
short-term climatic variations. They incorporate the responses of
crops to solar radiation, temperature, precipitation, and soil type,
and they
have been validated over a large range of climate and soil conditions
in the United States and other countries.
The major variable not considered by these and other existing
agricultural models is the direct "fertilization effect" of increased
levels of atmospheric carbon dioxide. Peart et al., therefore,
modified their models to consider both the increased rate of
photosynthesis and the increased water-use efficiency that corn and
soybeans have exhibited in field experiments.
Limitations
The analysis of combined effects is new research and will
need further development and refinement. The model runs use simple
parameters for C02 effects, assume higher atmospheric concentration C02
6-43
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Southeast
than are predicted, and may be overestimates of crop yields (see
Chapter 10 of this report).
The scenarios examining the effects of climate alone on
crops assumed that soils were relatively favorable for crops, with low
salinity or compaction, and assumed no limits on the supply of all
nutrients, except nitrogen. In addition, the analysis assumes no
technological adjustments are made by farmers to improve crop yields.
Possible negative impacts due to changes in storm frequency, droughts,
and pests and pathogens are not factored into this study.
Results
Soybean Yields. Table 6-8 illustrates the results of the
soybean model for 13 nonirrigated sites in the study area, as well as
Lynchburg, Virginia, a colder site included for comparison purposes.
The results differ between the wet GISS and dry GFDL scenarios. In
the GISS scenario, the cooler sites in Georgia and the Carolinas mostly
show declines in soybeans yields of 3 to 25%, and the other sites show
declines of 20 to 40%, ignoring CO2 fertilization. When the latter
effect is included, the Atlantic states experience gains of 11 to 39%,
and the other states vary from a 13% drop in Memphis to a 15% gain in
Tallahassee. (Tennessee fares worse than the North Carolina sites at
similar latitudes because its grid cell does not receive as favorable
an increase in water availability.)
By contrast, the dry GFDL scenario results in very large drops in
soybean productivity, with all but one site experiencing declines
greater than 50% and eight sites losing over 75%, considering only the
impact of climate change. Even when C02 fertilization is considered,
all but.four sites experience losses greater than 50%.
Corn Yields. Table 6-9 shows that the two scenarios differ
in a similar fashion for nonirrigated corn. However, in the case of
irrigated corn, where the analysis primarily reflects the impact of
temperature increases, the two scenarios show more agreement. Ignoring
CO2 fertilization, the GISS model shows drops of 13 to 20%, and GFDL
shows drops of 20 to 35%. When C02 fertilization is included, the GISS
scenario implies declines of less than 8% for all sites, and the GFDL
model shows similar declines for two sites and respective declines of
17 and 27% for Charlotte, North Carolina, and Macon, Georgia.
Irrigation. The two scenarios show more agreement for
agricultural fields that are already irrigated. Since the changes in
water availability are irrelevant here, the impacts are dominated by
the increased frequency of very hot days.
The results are mixed on whether currently dry land areas would be
shifted to irrigation. Table 6-10 shows the percentage increases in
6-44
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Chapter 6
Table 6-8
Impacts of 2xC02 Climate Change on Soybean Yields for
Selected Southeastern Sites (yield as a percentage of
current yield)
State
Climate Change
and COg Fertilization
GISS GFDL
Climate Change
Onlv
GISS
GFDL
Memphis , TN
Nashville, TN
Charlotte, NC
Raleigh, NC
Columbia, SC
Wilmington, NC
Atlanta, GA
Macon , GA
Tallahassee, FL
Birmingham, AL
Mobile, AL
Montgomery , AL
Meridian, MS
Lynchburg , VAa
87
104
132
139
118
125
127
111
115
100
92
90
91
146
30
79
12
24
38
59
33
18
83
71
error
32
36
45
62
70
93
97
80
89
89
75
80
69
66 .
61
63
101
18
48
8
13
22
38
22
9
49
46
57
16
22
26
Peart et al. investigate a number of sites in states adjacent to
the Southeast. Lynchburg is included to permit comparison of
Southeast results with a colder site.
Source: Peart et al, Volume .
6-45
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Southeast
Table 6-9. Impacts of 2xCO2 Climate Change on Corn Yields
Charlotte,
Scenario NC
Climate Change Only
Irrigated
GISS 87
GFDL 71
Rain fed
GISS 100
GFDL 24
Climate Change and C02
Irrigated
GISS 101
GFDL 83
Rainfed
GISS 116
GFDL 28
CO2 Fertilization Only
Irrigated 117
Rainfed 116
Macon, Meridian,
GA MS
81
65
98
18
Fertilization
92
73
114
20
113
116
80
80
84
30
93
93
98
36
117
116
Memphis ,
TN
82
80
93
37
95
94
113
37
1.18
116
Source: Peart et al, Volume .
6-46
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Chapter 6
Table 6-10. Increases in Corn Yields from a Shift to Irrigation
(percent, assuming no C02 fertilization)
State No Climate Change GISS GFDL
Memphis , TN
Nashville, TN
Charlotte, NC
Raleigh, NC
Columbia, SC
Wilmington, NC
Atlanta, GA
Macon , GA
Birmingham, AL
Mobile, AL
Montgomery, AL
Meridian , MS
Lynchburg, VA*
70
65
64
51
58
16
15
61
6
36
72
62
56
50
49
43
28
47
8
7
33
9
41
39
53
37
370
205
486
444
386
50
79
589
61
91
593
423
361
Source: Derived from Tables 6-8 and 6-9 (see text)
6-47
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Southeast
yields that would result from adding irrigation for no climate
change and the two climate change scenarios. All but four sites
could increase yields today by 50-75% by irrigating. Under the
wetter GISS scenario, irrigation only would increase yields
25-50%. However, under the dry GFDL scenario, irrigation would
increase yields by 200-600% that is, it would mean the
difference between crop failure and a harvest slightly above
today's levels in most years. Even without CO2 fertilization,
75% of the nonirrigated southeastern sites could gain more from
irrigation than they would lose from the change in climate
resulting from the GFDL scenario.
A farmer's decision to irrigate, shift to other crops, or
remove land from production would depend to a large degree on
what happens to future prices of both crops and water. Even
though water is plentiful today, the capital costs of irrigation
prevent most farmers in the Southeast from taking advantage of
the potential 50% increases in yields. But if crop failures due
to drought became as commonplace as Peart et al. project for the
dry GFDL scenario, a major increase in irrigation probably would
be inevitable.
Shifts in Production
Adams et al. (Volume ) examined the impacts of changes in
crop yields on farm profitability and cultivated acreage in
various regions of the United States. (The methods for this
study are discussed in Chapter 10: Agriculture) Their results
suggest that the impact of climate change on southeastern
agriculture would not be directly proportional to the impact on
crop yields (Table 6-11) .
Considering only the impact of climate change, Adams et al.
found that the GISS and GFDL scenarios would reduce crop acreage
by 10 and 16%, respectively. This is a small difference, given
Peart's projection that all but one site would lose more than
half of their production under the GFDL scenario, while none of
the sites would lose that much under the GISS scenario. When CO2
fertilization is considered, however, Adams et al. project
respective declines in farm acreage of 57 and 33% for the GISS
and GFDL scenarios.
The conclusion that the greatest decline in farming could
occur under the scenario in which yields increase is not
unreasonable in light of the substantial decline in farming that
took place during the period of rapid technical innovation after
World War II. As yields increase, prices decline. Adams et al.
project that most areas of the nation would lose farm acreage.
However, Adams et al. estimate that the Southeast would
experience the worst losses: while the Southeast has only 13% of
6-48
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Chapter 6
Table 6-11. Impact of Climate Change on Cultivated Land in the
Southeast
Region Baseline
Acreage (millions)
SE coast 12 . 5
Appalachia 15.5
Delta 19.9
Total 47.9
Percent loss
SE coast
Appalachia
Delta
Total
With Direct C02
GISS GFDL
8.7
2.8
9.3
20.8
30
82
53
57
7.8
7.4
16.7
31.9
38
52
16
33
Without Direct C02
GISS GFDL
11.5
14.1
17.7
43.3 .
8
9
11
10
11.2
12.9
16.2
40.3
10
17
19
16
Note: SE coast includes Florida, South Carolina, Georgia,
Alabama.
Appalachia includes North Carolina, Tennessee,
Virginia, West Virginia, Kentucky.
Delta includes Mississippi, Louisiana, Arkansas.
Source: Adams et al, Volume .
6-49
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Southeast
the cultivated acreage, it would account for 60-70% of the
nationwide decline in farm acreage.
When the CO2 fertilization effect is ignored, the reductions
in acreage would be much smaller, although the Southeast would
still account for 40-75%. The general decline in yields would
boost prices, which would make it economical for many farmers to
irrigate and thereby avoid the large losses associated with a
warmer and possibly dryer climate.
Agricultural Pests
The modeling and economic studies of agriculture do not
consider the impact of pests on crop yields. However, Stinner et
al. (Volume ) suggest that global warming would increase the
range of several agricultural pests that plague southeastern
agriculture. (See Chapter 10: Agriculture.for details on the
methods of this nationwide study.)
Stinner et al. point out that the northern ranges of potato
leafhoppers, sunflower moths, black cutworms, and several other
southeastern pests are limited by their inability to survive a
cold winter. Thus, milder winters would enable them to move
farther north, as illustrated in Figure 6-16. Stinner also
points out that more droughts could also increase the frequency
of pest infestations.
Implication of Agriculture Studies
Agriculture appears to be at least as vulnerable to a
potential change in climate in the Southeast as in any other
section of the country. Unlike many of the colder regions, the
benefits of a longer growing season would not appreciably offset
'the adverse impacts of warmer temperatures in the Southeast,
where cold weather generally is not a major constraint to
agricultural production.
Florida may present an important exception to the generally
unfavorable implications of climate change for crop yields.
Although Florida is the warmest state in the Southeast, its
agriculture appears to be harmed by cold temperatures more than
the agriculture of other states in the region. In recent years,
hard freezes have destroyed a large fraction of the citrus
harvest several times. As a result, the industry is moving south
into areas near the Everglades, and sugarcane, which also thrives
in warm temperatures, is expanding into the Everglades
themselves. Global warming could enable the citrus and sugarcane
areas to include most of the state. Warmer temperatures also
would help coffee and other tropical crops that are beginning to
gain a foothold in the state.
6-50
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SUNFLOWER MOTH
MOMOEOSOMA ELECTELLUM
GREEN CLOVERWORM
PLATHYPENASCABRA
POTATO LEAFHOPPER
EMPOASCA FABAE
BLACK CUTWORM
AGROTIS IPSILON
Figure 6-16. Present and predicted northern ranges of various
agricultural pests.
Source: Stinner et al, Volume .
6-51
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Southeast
Although Florida's surplus of water may make it the
exception, the current situation there highlights an important
aspect of climate change: Within the context of current prices
and crop patterns, the impact of climate change appears to be
unfavorable. However, warmer temperatures may present farmers
with opportunities to grow different crops whose prices would
justify irrigation or whose seasonal cycles would conform more
closely to future rainfall patterns.
Simulation Study of Southeastern Forests
Study Design
To assess the potential impact of climate change on
southeastern forests, Urban and Shuggart applied a forest
simulation model to a bottomland hardwood forest along the
Chattahoochee River in Georgia and to upland sites near
Knoxville, Tennessee; Macon, Georgia; Florence, South Carolina;
and Vicksburg, Mississippi. Their study considered the OSU,
GFDL, and GISS scenarios for doubled C02, as well as the GISS
transient A scenario through the year 2060.
The model these researchers used was derived from FORET, the
"gap" model originally developed by Shuggart and West (1977).
The model simulates forest dynamics by modeling the growth of
each tree in a representative plot of forest land. It keeps
track of forest dynamics by assigning each of 45 tree species
optimal rates of growth, seeding rates, and survival
probabilities, and by subsequently adjusting these measures
downward to account for less than optimal light availability,
temperature, soil moisture, and soil fertility. In the case of
the bottomland hardwood site, the model also considered changes
in river flooding, based on the flows in the lower Chattahoochee
calculated in the Lake Lanier study. The researchers applied the
model to both mature forests and the formation of a new forest
from bare ground.
Limitations
Urban and Shuggart caution against taking their results too
literally owing to a number of simplifying assumptions they had
to make. First, they had to assume that certain major species,
such as loblolly pine, could not tolerate more than 6,000
(cooling) degree-days per year. These species are not currently
found in warmer areas, but the southern limits of their range are
also limited by factors other than temperature: the Gulf of
Mexico and the dry climate of Texas and Mexico. Although the
6,000 degree-day line coincides with their southern boundary
across Florida, the peculiar environmental conditions of that
state make it impossible to confidently attribute an estimate of
thermal tolerance to that observation alone. Fortunately, this
6-52
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Chapter 6
caveat does not apply to most of the oaks, hickories, and other
species found in the cooler areas of the Southeast.
Another important caveat is that the model does not consider
the potentially beneficial impact of C02 fertilization on
photosynthesis, changes in water-use efficiency, or leaf area.
Results
The simulations by Urban and Shugart call into question the
ability of southeastern forests to be generated from bare ground,
particularly if the climate becomes drier as well as warmer. For
the Knoxville site, the dry GFDL scenario implies that a forest
could not be started from bare ground, while the GISS and OSU
2xC02 scenarios imply reductions in biomass of 10-25%. For the
South Carolina site, only the GISS climate would support a
forest, albeit at less than 50% of today's productivity. The
Georgia and Mississippi sites could not generate a forest from
bare ground for any of the scenarios.
The transient analyses suggest that mature forests could
also be lost not merely converted to a different type -if
climate changes. Figure 6-17 shows that none of the forests
would decline significantly before the year 2030; however, all
would decline substantially before 2060. The Mississippi forest
would mostly die by 2040, and the South Carolina and Georgia
sites by 2060. Only the relatively cool Tennessee site would
remain somewhat healthy, although biomass would decline 35%.
Although the simulation results suggest that southeastern
forests are unlikely to benefit from the global warming, the
impact on forests may not be as bad as the model suggests.
Nevertheless, major shifts in forest types are almost certain to
occur from the warmer temperatures alone.
Electric Utilities
Linder (Volume ) examined the impact of global warming on
the demand for electricity throughout the Southeast for the two
GISS transient scenarios. (See Chapter 16: Electricity Demand
for additional details on the methods and limitations of this
study.) Because Linder's study was limited to electricity, it
did not consider the reduced consumption of oil and gas for space
heating that would result from warmer temperatures.
Table 6-12 shows the percentage changes in electric power
requirements for various areas in the Southeast. Along the Gulf
coast, annual power requirements would increase 3-4% by 2010 and
6-53
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Chapter 6
Table 6-12.
Percentage Increases in Peak and Annual Demand for
Electricity by 2010 and 2055 Due to Climate Change
Area
GISS A (2010)
Annual Peak
GISS B (2010)
Annual Peak
GISS A (2055)
Annual Peak
North Carolina,
South Carolina,
Georgia
Florida
Eastern Tennessee
Alabama, Western
Tennessee
Mississippi
Louisiana
East Texas
1.6
2.7
1.6
1.9
3.8
2.9
3.1
7.3
4.9
3.7
3.8
7.6
7.6
7.9
1.3
2.7
1.3
2.2
4.4
2.7
2.8
2.4
3.6
1.2
5.7
11.4
6.6
6.6
5.9
9.3
5.9
6.8
13.6
10.2
11.3
24.4
20.0
12.2
13.5
26.9
23.4
25.3
Source: Linder and Inglis, Volume .
6-55
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Southeast
10-14% by 2055; elsewhere, the increases would be somewhat less.
Because peak demand for electricity generally occurs during
extremely hot weather, peak demand would rise more than annual
demand. Global warming could increase new generating capacity
requirement 10-24% by 2010 and 24-34% by 2055.
Linder compared increases in electric capacity required by
climate change with those necessitated by economic growth. He
estimated that through 2010, climate change could increase the
expected capital costs of $137 billion 6 to 9%; through 2055, it
could increase expected requirements of $350-500 billion by as
much as 20%.
OTHER STUDIES
Coastal Louisiana
An estuary accounting for half of the Southeast's wetlands
is also the most vulnerable: the delta at the mouth of the
Mississippi River. Because previous studies assessed the
vulnerability of Louisiana in detail, the current effort
supported no additional research into this issue.
Over the last few thousand years, the sediment washing down
the Mississippi River has formed the nation's largest delta at
the river's mouth, almost all of which is in Louisiana. Composed
mostly of marsh, cypress swamps, and small distributary channels
that carry water, sediment, and nutrients from the river to these
marshes and swamps, Louisiana's wetlands support half of the
nation's shellfish, one-fourth of its fishing industry, and a
large trapping industry. They also provide flood protection for
metropolitan New Orleans and critical habitats for bald eagles
and other migratory birds.
Water management and other human activities of the last 50
years are now causing this delta to disintegrate at a rate of
over 100 km2 (about 50 km2) per year. The delta has always
subsided as the sediment compacted, but the rate of sinking was
more than balanced by new sediment reaching the wetlands through
the distributaries and the annual river flooding. But that
sediment now largely washes into the deep waters of the Gulf
because flood-control and navigation guide levees confine the
flow of the river. Thus, the delta is gradually being submerged,
and cypress swamps are converting to open-water lakes as
saltwater penetrates inland. If current trends continue, almost
all of the wetlands will be lost in the next century.
A rise in sea level would'further accelerate the rate of
land loss in coastal Louisiana. As shown in Figure 6-18, even a
6-56
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3
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Southeast
50-cm rise in sea level (in combination with land subsidence)
would inundate almost all of the delta and would leave New
Orleans, most of which is below sea level and only protected with
earthen levees, vulnerable to a hurricane.
Strictly speaking, the entire loss of coastal Louisiana's
estuaries should not be attributed to global warming because the
ecosystem is already being lost. However, major efforts are
being initiated by the U.S. Army Corps of Engineers, the U.S.
Fish and Wildlife Service, the Louisiana Geological Survey,
several local governments, and other Federal and state agencies
to curtail the loss, generally by erecting structures to provide
freshwater and sediment to the wetlands. Technical staff
responsible for developing these solutions generally fear,
however, that a 1-m rise in sea level could overwhelm current
efforts, and that if such a rise is ultimately going to take
place, they already should be planning and implementing a much
broader effort (Louisiana Wetland Protection Panel, 1987).
IMPLICATIONS AND POLICY
Land Use
The impact of climate change on land use in the Southeast
must be examined in the context of the projected abandonment of
10-50% of the farmland in the Southeast and declines in forests.
A major issue is how this land will be used. In the past,
forests have been cleared for agriculture, and when abandoned,
they have been converted to forest again. But the forest models
suggest that the impact of climate change on the generation of
new forests from bare ground would be even more adverse than the
impact on existing forests. If the forest simulations are
correct, the abandoned fields would become grasslands or
overgrown with weeds, and the Southeast could gradually come to
resemble the scenery found today in the Great Plains.
Water Resources
The water resource "problems" faced by the Southeast are the
type that would make western water managers envious. Rainfall
and runoff would increase in the GISS scenario. Although most
other assessments suggest that runoff would decline, the
magnitude of the decline does not appear to threaten the
availability of water for municipal, industrial, or residential
use. However, the nonconsumptive uses for hydropower,
navigation, environmental quality, and recreation could be
threatened. Although sufficient time exists to develop rational
strategies to implement the necessary tradeoffs, current Federal
statutes in a rigorous fashion discourage water managers from
formally considering them.
6-58
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Chapter 6
Impacts of Wetter Climate
Although most water resource problems have been associated
with too little water, it does not necessarily follow that a
wetter climate would be generally beneficial. The designs of
water management infrastructure and the location of development
along lakes and rivers have been based on current climate.
Hence, shifts in either direction would create problems.
The chief problem from a wetter climate would be more
flooding, particularly in southern Florida and coastal Louisiana,
where water often lingers for days and even weeks after severe
rainstorms and river surges. Inland communities, such as
Chattanooga, also might face flooding if wetter periods exceed
the ability of dams to prevent flooding.
Impacts of Drier Climate
A drier climate, on the other hand, would exacerbate
current conflicts over water use during dry periods. Hydropower
would decline, increasing the need to use fossil or nuclear
power, both of which would require more water for cooling.
Conflicts between municipal water users and recreational
interests also would intensify. Lake levels could drop more
during the summer, even if municipal use of water did not grow.
However, warmer temperatures probably would increase municipal
water demand for cooling buildings and watering lawns.
These conflicts could be further exacerbated if farmers
increase the use of irrigation. Groundwater is available in
reasonably shallow aquifers that drain into rivers. Any
consumptive use of water from these aquifers would reduce, and in
some cases reverse, the base flow of water from aquifers into
these rivers. Water also could be drawn directly from rivers for
irrigation in some areas.
A decline in riverflows could be important for both
navigation and environmental quality. For the Tennessee, as well
as the Chattahoochee and other small rivers, adequate reservoir
capacity exists to maintain flows for navigation, if this use
continues to take precedence over water supply and recreation.
However, the 1988 drought has graphically demonstrated that there
are not enough dams to guarantee navigation in the Mississippi.
If this situation became more commonplace, the economic impact on
New Orleans could be severe. On the other hand, traffic on the
Tennessee and Ohio Rivers might use the Tennessee-Tombigbee Canal
as an alternative, which would benefit the port of Mobile.
6-59
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Southeast
Lower flows also would reduce the dilution of municipal and
industrial effluents discharged into rivers and would decrease
the level of dissolved oxygen. This would harm fish populations
directly, and indirectly by reducing the abilities of streams to
assimilate wastes. Reduced flows also would threaten bottomland
hardwood and estuarine ecosystems. To prevent these problems,
factories and powerplants might have to more frequently erect
cooling towers or curtail their operations.
Is Current Legislation Adequate?
The same issues that face the TVA and Lake Lanier would
likely face decisionmakers in other areas. Federal laws
discourage water managers in the Southeast from rigorously
evaluating the tradeoffs between the various uses of water. Most
dams are more than sufficient to meet the statutory requirements
for navigation and flood safety and to continue generating
substantial hydropower on demand. Consequently, there has been
little need to analyze the tradeoffs between these factors. For
example, a literal application of the law would not allow the
Corps of Engineers to cut hydropower production or navigation
releases to ensure a supply of water for Atlanta. Therefore,
agencies have not analyzed the allocation of water that best
serves the public for various levels of water availability
(although the TVA is beginning to do so) .
At a practical level, Federal water managers have shown
flexibility, as in the case of cutting navigation along the
Chattahoochee instead of further cutting Atlanta's water supply.
If climate changes and more than a modest level of flexibility is
necessary, water resource laws could be changed; the physical
infrastructure.is .largely in place to address water problems of
the Southeast. But until the laws are changed, the Federal
agencies in the Southeast often would be forced to allocate water
inefficiently. Moreover, people making decisions concerning
siting of recreational and industrial development, long- term
water supply sources, powerplant construction, and other
activities sensitive to the availability of water would risk
basing their decisions on incorrect assumptions regarding the
future allocation of water.
Estuaries
Coastal plants and animals across the Southeast may have
difficulty surviving warmer temperatures. For example, along the
northern coast of the Gulf of Mexico, several types of fish spend
at least part of their lifetimes in estuaries that are already as
hot as they can tolerate. If climate becomes warmer, however,
migrating north would not be feasible. While these species could
6-60
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Chapter 6
escape the summer heat by fleeing to the cooler waters of the
gulf, such a flight would make them vulnerable to larger fish.
Although the gulf coast estuaries are the warmest, estuaries
as far north as North Carolina reach temperatures only about 3 °
cooler than those that prevail in the Apalachicola estuary.
Thus, all southeastern estuaries are likely to lose at least as
great a proportion of their oysters, shrimp, and crabs to high
temperatures as the Apalachicola loses today, and most would lose
more.
In addition to the direct effect of climate change on
estuaries, human responses to climate change and sea level rise
also could hurt coastal estuaries. The flood control works
erected in response to disasters in Florida and along the
Mississippi River now appear to be destroying the Everglades and
coastal wetlands of Louisiana. Additional flood control levees
and bulkheads to stop erosion could result in additional wetland
loss, as discussed in Chapter 9: Sea Level Rise. Increased
reservoir construction would decrease the amount of sediment
flowing down the river arid nourishing the wetlands. If the
climate becomes drier, irrigation could further reduce freshwater
flow into estuaries.
To a large extent, the policy implications for wetland loss
in the Southeast are similar to those facing the rest of the U.S.
coastal zone. Previous studies have identified several measures
to reduce the loss of coastal wetlands in response to sea level
rise (e.g., Office of Wetland Protection, 1988; Titus, 1988).
These measures include the following:
o increase the ability of wetlands to keep pace with sea
level,
o remove impediments to landward creation of new wetlands,
and
o dike the wetlands and artificially maintain water levels.
All of these measures are being employed or actively considered.
Congress has authorized a number of freshwater and sediment
diversion structures to assist the ability of Louisiana's
wetlands to keep up with relative sea level rise. These
structures are engineered breaches in river levees that act as
spillways into the wetlands when water levels in the river are
high. Although decisions on where to build diversion structures
are being based on current climate and sea level, consideration
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Southeast
of global warming would substantially change the assumptions on
which current analyses are being based and the relative merits of
alternative options. More frequent or higher surges in the
Mississippi River would increase the amount of water delivered to
the wetlands. And if climate change resulted in more soil
erosion, more sediment might also reach the wetlands; lower flows
could have the opposite effect. Sea level rise might shorten the
useful lifetimes of these projects, but because the
flood-protection benefits of protecting coastal wetlands would be
greater with a higher sea level, the economic justification of
these projects would not necessarily be undermined by the
prospect of sea level rise. Nevertheless, they would change the
relative merits of alternative options (Louisiana Wetland
Protection Panel, 1987).
Artificially managing water levels also has been proposed
fof Louisiana, particularly by Terrebonne Parish, whose eastern
wetlands are far removed from a potential source of sediment.
Such an approach also might be possible for parts of Florida,
where wetlands already are confined by a system of dikes and
canals, and water levels already are managed. Although no one
has yet devised a practical means by which shrimp and other fish
could migrate between ocean and estuary, other species spend
their entire lifetimes within the estuary, and freshwater species
could remain in artificially maintained freshwater wetlands.
A final response would be to accept the loss of existing
wetlands, but to take measures to prevent development from
blocking the landward creation of new wetlands. This approach
has been enacted by the state of Maine (1987) and would be
consistent with the proposals to discourage bulkheads that have
been widely discussed by coastal zone managers and enacted by the
state of South Carolina. Titus Greene estimates that 1800 mi of
wetlands in the Southeast could be created if developed areas
were not protected. Although this area represents a small
fraction of the potential loss, it would increase the remaining
areas of wetlands by 30-90%, and it would maintain and perhaps
increase the proportion of shorelines on which at least some
wetlands could be found.
Beach Erosion
The implications of sea level rise for recreational beaches
in the Southeast are similar to the implications for the mid-
Atlantic and the Northeast. If shore-protection measures are not
taken, the majority of resorts will have no beach at high tide by
2025 under the midrange scenario of future sea level rise. The
cost of undertaking the necessary measures through 2025 would
probably be economically justified for most resorts (see Chapter
9: Sea Level Rise). However, the cost of protecting all
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Chapter 6
recreational beaches through 2100 would be $100 to $150 billion,
which would probably lead some of the more vulnerable areas to
accept a landward migration much as areas on North Carolina's
Outer Banks are facing today.
The potential responses to global warming should be viewed
within the context of current responses to erosion flooding.
Florida has a trust fund to nourish its beaches and has received
Federal assistance for pumping sand onto the shores of Miami
Beach. Although Mississippi has no reason to combat the landward
migration of its barrier islands, it has nourished the beaches of
Biloxi, Gulfport, and other resort communities that lie on the
mainland along the protected waters behind the barriers.
Louisiana is rebuilding its undeveloped barrier islands because
they protect the mainland from storms. Most states have employed
a variety of structural solutions, such as groins (jetties) and
seawalls. However, they are moving toward "soft engineering"
solutions, such as beach nourishment, because of doubts about the
effectiveness of hard structures in universal erosion and their
interference with recreational uses of the beach.
Land-use measures also have been employed to adapt to
erosion. Because of unusually high erosion rates on the Outer
Banks, houses along the coast are regularly moved landward.
North Carolina requires houses, hotels, and condominiums to be
set back from the shore by the distance of a 100-year storm plus
30 years' worth of erosion on the assumption that after 30 years,
the house could be moved back. To maintain the integrity of its
publicly owned recreational beaches and to discourage shorefront
property owners from expecting state efforts to protect these
beaches, Texas requires that any house left standing in front of
the vegetation line after the shore erodes must be torn down.
If a global warming increases the frequency of hurricanes, a
number of southeastern communities will be devastated. There is
no way to know which communities might experience a hurricane
resulting from the greenhouse effect. However, the overall
impact of increased hurricane frequency would be small compared
to the impact of sea level rise. While a doubling of hurricanes
would convert 100-year floodplains to 50-year floodplains
throughout much of the Southeast, a 1-m rise would convert them
to 15-year floodplains.
Because the open-coast areas most vulnerable to sea level
rise are generally recreational beach resorts, the costs of
erosion and flooding should be viewed within the larger context
of why people go to the beach. People from the north visit
southeastern beaches to escape winter, and residents of the
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Southeast
region go to escape the summer heat. As temperatures become
warmer, Georgia and the Carolinas will be able to compete with
Florida for northerners. Hotter temperatures also may increase
the desire of the region's residents to visit the beach.
Thus, it is possible that the cooler communities will reap
benefits from a longer and stronger tourist season that are
greater than the increased costs for erosion control. Areas that
already have a year-round season are less likely to benefit, and
in a few areas like Miami Beach, the off-season may be extended.
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Chapter 6
REFERENCES
Armentano, T.V., R.A. Park, and C.L. Cloonan. 1988. Impacts on
Coastal Wetlands Throughout the United States." In Titus (ed)
1988. op. cit.
Earth, M.C. and J.G. Titus. 1984. Greenhouse Effect and Sea
Level Rise: A Challenge for This Generation. New York: Van
Nostrand Reinhold Company.
Bureau of Economic Analysis. Department of Commerce. 1986.
Bureau of the Census. Department of Commerce. 1982 Census of
Agriculture. Vol. 1. Geographic Area Series.
Bureau of the Census. Department of Commerce. 1988.
Statistical Abstract of the United States: 1988.
Burnash Robert J.C., R. Larry Ferral, and Richard A. Mcguire.
1973. "A Generalized Streamflow Simulation System, Conceptual
Modeling for Digital Computers." National Weather Service and
California Department of Water Resources. Sacramento,
California.
Edison Electric Institute. 1985. Statistical Yearbook of the
Electric Utility Industry.
Energy Information Administration. May 1988. Electric Power
Monthly.
Fisheries Statistics Division, National Marine Fisheries Service,
NOAA. 1987 Preliminary Statistics for United States Domestic
Catch.
Geraghty, J., D. Miller, F. Van Der Leeden, and F. Troise. 1973.
Water Atlas of the United States. Water Information Center, Port
Washington, N.Y.
Gibbs, M. 1984. Economic analysis of sea level rise: Methods
and results. In Earth and Titus 1984.
Healy, Robert G. 1985. Competition for Land in the American
South. Washington, D.C.: The Conservation Foundation.
Jenkins, Representative, Rep. Barnard, and Rep. Darden. 1988.
HR-4254: Georgia Resevoir Management Act of 1988. 100th
Congress. 2nd session.
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Southeast
Jones, C.A. abd J.R. Kiniry (eds.). 1986. CERES-Maize: A
simulation model of maize growth and development. College
Station, Texas: Texas A&M Press.
Kana, T.W., J. Michel, M.O. Hayes, and J.R. Jensen. 1984. The
physical impact of sea level rise in the area of Charleston,
South Carolina. In Earth and Titus (eds) 1984.
Leatherman, S.P. 1984. Coastal geomorphic responses to sea
level rise: Galveston Bay, Texas. In Earth and Titus (eds)
1984.
Linder, K.P., M.J. Gibbs, and M.R. Inglis. 1988. Potential
Impacts of Climate Change on Electric Utilities. New York, N.Y.:
New York State Energy Research and Development Authority.
Louisiana Wetland Protection Panel. 1987. Saving Louisiana's
Coastal Wetlands: The Need for a long-term Plan of Action.
Washington, DC: U.S. Environmental Protection Agency/Louisiana
Geological Survey. EPA-230-02-87-026.
Meo, M. 1987.- Proceedings of the Symposium on Climate Change in
the Southern United States. Norman, OK: University of Oklahoma.
Mitch, W. and J. Gosselink. 1986. Wetlands. New York: Van
Nostrand Reinhold Company, Inc.
Shugart, H.H. and D.C. West. 1977. Development of an
Appalachian deciduous forest succession model and its application
to assessment of the impact of the chestnut blight. Journal of
Environmental Management. 5:161-179.
Titus, J.G., C.Y. Kuo, M.J. Gibbs, T.B. LaRoche, M.K. Welts, and
J.O. Waddell. 1987. Greenhouse effect, sea level rise, and
coastal drainage systems. J. Water Res. Planning and Management
ASCE 113(2):216-227.
Titus, J.G. 1987. "The Greenhouse Effects, Rising Sea Level,
and Society's Response." In: R.J.N. Devoy. 1987. Sea Surfact
Studies Croom Helm: New York.
Titus, J.G. 1988. Greenhouse Effect, Sea Level Rise, and
Coastal Wetlands. Washington, D.C.: U.S. Environmental
Protection Agency.
Titus, J.G. 1988. "Sea Level Rise and Wetland Loss: An
Overview." In Titus (ed). op. cit.
Titus, J.G. 1984. Planning for Sea Level Rise Before and After a
Coastal Disaster. In: Earth, M.C. and Titus, J.G. (eds).
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Chapter 6
Greenhouse Effect and Sea Level Rise: A Challenge for This
Generation. New York: Van Nostrand Reinhold Company.
Wilkerson, G.G., J.W. Jones, K.J. Boote, and J.W. Mishoe. 1985,
SOYGRO V5.0: Soybean Crop Growth and Yield Model. Technical
Documentation. Gainesville, FL: University of Florida.
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Southeast
Table 6-11. Impact of Climate Change on Cultivated Land in the
Southeast
With Direct C02 Without Direct C02
Region Baseline GISS GFDL GISS GFDL
Acreage (millions)
Southeast 12.5 8.7 7.8 11.5 11.2
coast
Appalachia 15.5 2.8 7.4 14.1 12.9
Delta 19.9 9.3 16.7 17.7 16.2
Total 47.9 20.8 31.9 43.3 40.3
Percent loss
Southeast 30 38 8 10
coast
Appalachia
Delta
Total
82
53
57
52
16
33
9
11
10
17 .
11
16
Note: SE coast includes Florida, South Carolina, Georgia,
Alabama.
Appalachia includes North Carolina, Tennessee, Virginia,
West Virginia, Kentucky.
Delta includes Mississippi-, Louisiana, Arkansas.
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CHAPTER 7
GREAT PLAINS
FINDINGS
Global warming in the Great Plains may reduce agricultural
output, increase irrigation demand, change water quality, and
increase electricity needs.
Agriculture
o Generally, the effects of a warmer climate alone would
reduce wheat and corn yields. Yield changes range from +15
to -90%. The direct effects of C02 on crop photosynthesis
and water use may mitigate these effects, unless climate
change is severe.
o Crop yields in southern areas, such as Texas and Oklahoma
may decline relative to northern areas of the United States.
This change in productivity could lead to a 4 to 22 percent
reduction in cultivated acreage in the Great Plains.
o Because of the increased reliability of yields from
irrigated lands relative to dryland yields, and because of
higher crop prices, demand for irrigation water on remaining
farms will probably increase. The number of acres irrigated
may increase by 5 to 30 percent.
Water Quality
o Water quality in the southern Great Plains would be altered
due to changing pesticide loadings in surface runoff and
erosion. Quality of groundwater may be less at risk than
surface water quality, because of increased evaporation and
less leaching. These results are very sensitive to changes .
in the amounts and frequency of rainfall.
Electricity Demand
o The annual demand for electricity in Kansas, Nebraska,
Oklahoma, and West Texas could rise by 5 to 10 billion
kilowatt hours (2 to 4 percent) by 2010 and by 41 to 81 BKWH
(10 to 14 percent) by 2055.
o By 2010, approximately 3 to 6 gigawatts would be needed to
meet the increased demand and by 2055, 22 to 45 GW would be
needed a 27 to 39 percent increase over baseline
additions that may be needed without climate change the
cumulative cost of these additions by 2055 would be $24 to
$60 billion.
7-1
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Great Plains
Agencies with responsibility for agricultural land use, such
as the USDA Agricultural Stabilization and Conservation
Service and the Soil Conservation Service, could begin to
analyze how their missions may be affected by climate change
and to consider development of flexible strategies to deal
with potential impacts. Water resource managers, such as
those on the River Basin cimmissions and in State natural
resource agencies, may wish to factor the potential effects
of cllimate change into planning of long-term irrigation,
drainage, and water-transfer systems.
CLIMATE-SENSITIVE ASPECTS OF THE GREAT PLAINS
Agriculture
The Great Plains consist of a treeless region of relatively
flat topography between the Rocky Mountains and the Mississippi
lowlands of central North America. Since agricultural settlement
began in the late 1800s, the area has developed into a key small-
grains agricultural production region. The southern Great Plains
developed rapidly as a wheat production area and became an
extensive dryland agricultural region dominated by the
cultivation of wheat (Figure 7-1). In the last two decades,
exploitation of water from the Ogallala Aquifer has led to the
development of significant irrigated agricultural production. In
many areas, irrigated farming of corn, rice, and cotton has
replaced dryland wheat production, especially in western Kansas
and the Texas Panhandle (Figure 7-1).
The Great Plains portions of Kansas, Nebraska, Oklahoma, and
Texas constitute a vital part of the United States' agricultural
base. Nearly 100,000 farms encompassing over 111 million acres'
produce an important array of dryland and irrigated crops. Major
dry farming crops include winter wheat and grain sorghum, and
irrigated grains include corn and rice. In all, the four States
produce over 80, 40, and 15%, respectively, of the nation's grain
sorghum, wheat, and corn (Table 7-1).
7-2
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s*
OGALLALA
AQUIFER
| j DRYLAND FARMING AREA
Figure 7-1. Dryland wheat production in Great Plains,
Source: Science of Food and Agriculture (1987, 1988),
7-3
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Great Plains
TABLE 7-1. U.S. Agricultural Ranking and Percent of U.S. Total for
Selected Products, 1982.
Kansas Nebraska Oklahoma Texas % U.S. Total
Sorghum harvested 2 3 5 1 80.5
Cattle fattened on 2 3 9 I 46.7
grain and concen-
trates sold
Value of cattle 2 3 7 1 40.7
and calves sold
Wheat harvested 1 9 3 6 31.8
Cotton harvested 9 2 25.8
Hay harvested 9 2 16 "7 15.9
Market value of 6 5 20 3 18.5
all agricultural
products
Source: 1982 Census of Agriculture. U.S. Bureau of the Census. 1983.
U.S. Government Printing Office. Washington, D.C.
7-4
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Chapter 7
Livestock constitute another important agricultural
commodity in the region. Almost 50% of-all cattle fattened in
the country are raised in the four States, accounting for 40% of
the total U.S. value of marketed livestock.
In addition to contributing substantially to national
production, the four States are also major exporters of
agricultural products. Foreign exports of grain and animal
products are especially notable (Table 7-2). In total, these
four States provide approximately one-fifth of the dollar value
of all U.S. agricultural exports. Yet, dependence on foreign
markets puts Great Plains farmers at high risk. While large
historical fluctuations in grain and livestock production levels
are partly related to climatic variability, changing
international markets have also played an important role in the
region's failure to achieve long-term economic and social
stability.
Farmers in the Great Plains have been particularly
vulnerable to climate variability. The southern and central
Great Plains States of Nebraska, Kansas, Oklahoma, and Texas, the
focus of this regional case study, were among the hardest hit
during the Dust Bowl of the 1930s (Worster, 1979; Hurt, 1981).
Yields of wheat and corn dropped as much as 50% below normal,
causing the failure of about 200,000 farms and migration of more
than 300,000 people from the region.
The Dust Bowl, other droughts, and the desire for continued
expansion and intensification of dryland farming have led-to
numerous technological and social adjustments to climate and
market fluctuations. Especially critical, from a dryland farming
perspective, has been the improvement of conservation tillage
practices (Warrick and Bowden, 1981; Riebsame, 1983). These
practices, now prescribed for the area, aim to conserve moisture,
reduce energy input, and minimize erosion, thus increasing yields
and profits.
Besides the developments in cropping systems, policies have
also been devised to absorb or mitigate the impacts of climate
stresses. These include Federal programs for crop insurance,
disaster grants and low-interest loans to farmers, and
Government-sponsored drought research (Warrick, 1980). Such
programs can be costly. For example, the Drought Relief Bill
proposed for the current drought of 1988 is projected to cost
about $3.9 billion nationally (New York Times, 1988).
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Great Plains
Table 7-2. Agricultural Exports from Selected Plains States, Fiscal Year
1984 (Millions of Dollars).
Feed grains and
products
Wheat and
products
Live animal and
meats
All agricultural
products
U.S.
7,585
4,526
1,161
31,187
Kansas
372
797
130
1,719
Nebraska
903
150
134
1,762
Oklahoma Texas
385
353 276
18 161
71 2,031
% U.S. Total
22
35
38
19
Source: USDA Economic Research Service. 1985. Foreign Agricultural Trade
of the United States. Washington, D.C.
7-6
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Chapter 7
The Great Plains is one of the most marginal agricultural
regions in the United States. Some observers feel that the
southern Plains are simply too sensitive to climatic swings and
that intensive dryland farming should be abandoned (Worster,
1979). Yet in a wet year, the Plains produce bumper crops of
small grains that add significantly to the nation's export trade
balance.
Despite the adoption of conservation tillage techniques,
drought-resistant cultivars, and risk management programs, some
analysts argue that the region remains particularly vulnerable to
climate-induced reductions in crop yields and might manifest the
first impacts of climate change (e.g., Lockeretz, 1978). Rapid
acreage increases in the 1970s, destruction of windbreaks for
larger fields to accommodate bigger machinery, and speculative
farm expansion all raise the specter of renewed land degradation
similar to that of the Dust Bowl period, if climate change
creates an increased frequency of heat waves and droughts in the
region.
The Ogallala Aquifer
A major response to the semiarid and highly variable climate
of the Great Plains has been exploitation of surface and
groundwater resources for irrigation. In 1982, 75,000 km2, or
12% of all Great Plains cropland, were irrigated. Groundwater
provides most of the water for irrigation: 61-86% of the water
used in Nebraska, Oklahoma, and Kansas compared with only 20%
nationally.
The improvement and application of well drilling and pumping
technology after World War II permitted the use of water from the
immense Ogallala Aquifer (Figure 7-1). Today, the aquifer
supplies irrigation for approximately 14 million acres in the
Great Plains States of Colorado, Nebraska, Kansas, Oklahoma, New
Mexico, and Texas (High Plains Associates, 1982). Use of the
aquifer allows the irrigation of upland terrain previously too
far from surface supplies. The aquifer also provides water for
municipal and industrial purposes.
Nebraska recently started to use the aquifer to irrigate
corn, which is grown mostly for livestock feed. Corn, wheat, and
some sugar beets are irrigated further south, while in Texas the
Ogallala is tapped chiefly for cotton. The aquifer varies in its
depth from the surface of the land, its rate of natural
discharge, and its saturated thickness in different regions.
Nebraska has a higher recharge rate (i.e., the rate at which the
aquifer is replenished) than the other Great Plains States and
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Great Plains
has not yet suffered significant drawdown problems. In Texas,
high withdrawal and low recharge rates of the aquifer have
already resulted in "mining" of the resource (i.e., the rate of
water withdrawal is greater than rate of recharge) and in the
abandonment of thousands of irrigated acres (see Wilhite, Volume
PREVIOUS CLIMATE CHANGE STUDIES
Several studies of climate change impacts on agriculture in
the Great Plains have been performed, using a variety of
approaches and models. Warrick (1984) considered the
vulnerability of the region to a possible recurrence of the 1930s
drought. Using a crop yield model tuned to 1975 technology,
Warrick found tha.t a recurrence of 1934 and 1936 conditions on
the Plains would result in wheat yield reductions of over 50%.
Terjung et al. (1984) investigated water regimes for corn
production under differing climate change scenarios, using a crop
water-use and yield model. They found that the middle latitudes
of the Great Plains were the most sensitive to the climate change
scenarios both in evapotranspiration and total water applied for
irrigation. This modeling work was continued by Liverman et al.
(1986) , who found that the lowest irrigated yields occurred under
cloudy, hot, and very dry climate change scenarios. Under
dryland conditions, minimum yields occurred under sunny-hot and
sunny-warm scenarios with very dry conditions.
Using an agroclimatic approach, Rosenzweig (1985) found that
lack of cold winter temperatures in the southern Great Plains may
necessitate a change from winter to spring wheat cultivars.
Decreased water availability may also increase demand for
irrigation. In a later study, Rosenzweig (1987) showed
that although the combined effects of climate change and
increased C02 compensated for the negative effects of climate
change in years with adequate rainfall, many simulated crop
failures occurred in years with poor weather.
Robertson et al. (1987) estimated the combined impact of
climate change and increased CO2 on corn and wheat yields and
erosion using the Erosion Productivity Impact Calculator (EPIC) .
Modeled wheat yields in Texas decreased and modeled corn yields
increased only marginally due to moisture stress.
Glantz and Ausubel (1984) suggested that the Great Plains'
mining of the Ogallala Aquifer and its susceptibility to future
incidence of drought projected by global climate change models be
7-8
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Chapter 7
combined in analyses of the region, since both are critical to
the habitability of the area.
GREAT PLAINS STUDIES IN THIS REPORT
The EPA studies for this report examine the implications of
climate change for agricultural production and economics, demand
for irrigation water, and water quality. Climate change impact
research on energy use and resource management policy relevant to
the Great Plains are also described.
The studies performed for this report are listed in Table
7-3.
SUMMARY OF CLIMATE CHANGE SCENARIOS FOR THE GREAT PLAINS
The predicted changes in seasonal and annual temperatures
and precipitation for all three scenarios are shown in Figure 7-
2. All three scenarios show large increases in temperature for
the Great Plains States under a doubled C02 climate. The GISS
scenario has an average warming of 4.5°C, the GFDL scenario has a
warming of 4.9°C and OSU has an average warming of 3.3°C. In
general, winter temperatures increase more than summer
temperatures in the GISS model, summer temperature changes are
greater than winter temperature changes in the GFDL and OSU
scenario. The studies used only the GISS and GFDL climate change
scenarios.
Annual precipitation decreases by 0.26 mm/day in the GISS
scenario, and 0.12 mm/day in the GFDL while OSU has a slight
increase. However, these annual values mask a pronounced
reduction in rainfall in Nebraska and Kansas in the GFDL scenario
(see Figure 7-3). The large temperature increase and pronounced
summer drying in these states combine to make the GFDL scenario
more severe than the GISS scenario for the Great Plains.
The magnitudes of climate changes from the GFDL scenario and
the climate of the 1930s drought in Nebraska and Kansas are
compared in Figure 7-3. While the predicted decreases in
precipitati.on are about the same as those during the most severe
drought years (1934 and 1936) in the area, CO2-induced
temperatures are predicted to be about 3°C higher than the Dust
Bowl temperatures.
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Great Plains
Table 7-3. Great Plains Studies for EPA Report to Congress on the
Effects of Global Climate Change
Analyses Performed for This Case Study
o Potential Effects of Climate Change on Agricultural
Production in the Great Plains: A Simulation study
Cynthia Rosenzweig
Department of Geography, Columbia University
NASA/Goddard Institute for Space Studies
o Effects of Projected CO2-Induced Climatic Changes on
Irrigation Water Reguirements in the Great Plains States
Richard G. Allen
Utah State University
National Studies That Included Great Plains Results
o Economic'Effects of Climate Change on U.S. Agriculture:
A Preliminary Assessment
Richard M. Adams
Oregon State University
o Impacts of Climate Change on the Movement of Agricultural
Chemicals Across the U.S. Great Plains and Central Prairie
Howard L. Johnson
Oklahoma Climatological Survey
University of Oklahoma
o The Potential Impacts of Climate Change on Electric
Utilities: Regional and National Estimates
Kenneth P. Linder
ICF Incorporated
o Adjusting Resource Management Policy to Climate Change
William E. Riebsame
University of Colorado
7-10
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I
1
3 h-
2 h
P
//>
OSS
GFDL
osu
WMv
Sunmtr
Anrearf
0.2
0.1
>- -0.1 l-
<
O
<2 -0.2
2
.0.4
-0.9 H
-0.6
I
I
Sprtig Sumrar
Fal
Annul
Figure 7-2
Average change in (a) temperature and (b)
precipitation over Great Plains gridpoints (2XCO2
less 1XCO2) .
7-11
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M
P
c
R
A
T
U
R
C
H
A
N
G
t
C
E
L
5
i
U
s
1934 + 1936
GFDL
C
h
a
n
9
d
a
y
CHI]
1934 + 1936
GFDL
Figure 7-3.
Comparison of observed drought and GFDL climate
change for (a) temperature and (b) precipitation.
7-12
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Chapter 7
RESULTS OF THE GREAT PLAINS STUDIES
Crop Production
To better understand the potential physical impact of
climate change on crops, Rosenzweig modeled changes in corn and
wheat yields in the Great Plains using crop growth models.
Study Design
The crop growth models, CERES-Wheat (Ritchie and Otter,
1985) and CERES-Maize (Jones and Kiniry, 1986), were used to test
the sensitivity of crop yields to the GISS and GFDL climate
change scenarios. These models are designed for large-area yield
prediction and for farm decisionmaking.
They respond to a wide range of soil, climatic, and planting
conditions. The models have a whole-plant framework.
At each of 14 locations, the crop models were run on three
soils present in the region representing low, medium, and high
productive capacity. Model results were generated for change of
yield, water used for irrigation (if crop is irrigated), crop
evapotranspiration, and planting and maturity dates for both
dryland and irrigated cases.
The direct effects of C02, i.e., increased photosynthesis
and decreased transpiration per unit leaf area, were simulated
with the climate change scenarios in another set of runs. A
method for approximating the direct effects was developed by
computing ratios of daily photosynthesis and evapotranspiration
rates of a canopy exposed to elevated C02 to the corresponding
rates of the same canopy if exposed to ambient C02 conditions
(see Peart et al., Volume _).
Limitations
This work does not consider changes in frequencies of
extreme events, even though extremes of climatic variables,
particularly runs of extremes, are critical to crop productivity
(see Mearns, Volume _). Development of the CERES models was
based on current climate; the relationships in the models may or
may not hold under differing climatic conditions, particularly
the high temperatures predicted for the greenhouse climate.
The direct effects of C02 are only approximated in the crop
modeling study, because the models do not include a detailed
simulation of photosynthesis. Also, experimental results from
7-13
-------
Great Plains
controlled environments may show more positive effects of C02
than will actually occur in variable, windy, and pest- infected
(e.g., weeds, insects, and diseases) field conditions.
Results
Climate change scenarios cause simulated wheat and corn
yields to decrease in the southern and central Great Plains.
Decreases in modeled yields appear to be caused primarily by
increases in temperature, which shorten the duration of crop life
cycle (the period during which crops grow) . This results in
reduced yields. Wheat yields decrease more at lower latitudes.
The changes in corn yields are displayed in Figure 7-4.
When the direct effects of C02 on crop photosynthesis and
transpiration are included in the climate change simulations,
modeled crop yields overcome the negative effects of climate
change in some cases, but not in others (Figure 7-5) . The more
severe the climate change scenario, the less compensation
provided by direct effects of
The amount of water needed for irrigation increases in the
areas where precipitation decreases. Irrigation appears to
reduce interannual variability in yields.
Adjusting the planting date of wheat to later in the fall
does not significantly ameliorate the effects of the GISS climate
change scenario on CERES-Wheat yields. Changing to varieties
with lower vernalization requirements (period of cold weather
necessary for reproduction) and lower photoperiod sensitivity
(sensitivity to daylength) , in addition to delaying planting
dates, overcomes yield decreases at some sites but not at others.
Implications
With high temperatures, increased irrigation may be needed
to produce acceptable and stable yield levels. This could place
increased demand on the already depleted Ogallala Aquifer and
other water resources in the region.
Regional Agricultural Shifts
Many economic consequences are likely to result from the
physical changes in crop yields and water availability caused by
climate change. Adams et al. introduced yield changes from the
Great Plains and other regional crop modeling studies and changes
in water demand and availability from the GISS and GFDL scenarios
into an economic model to translate the physical effects of
7-14
-------
a)
WHEAT MODEL YIELDS:
COMBINED CLIMATE AND DIRECT EFFECTS
DRYLAND
36-38 N
LATITUDE
34-36 N
<34 N
BASE 1951-19SC
J'SS CC * DE
j G-:. cc - DE
b)
WHEAT MODEL YIELDS:
COMBINED CLiMATE AND DIRECT EFF'ECTS
AUTOMATIC IRRIGATION
40-42 N
38-40 N
36-38 N
LATITUDE
34-36 N
<34 N
3ASE 1951-1980
3!SS CC + DE 1 I GfDL CC + DE
Figure 7-4. CERES-Wheat yields with climate change scenarios
alone: (a) dryland (b) irrigated
Source: Rosenzweig, Volume .
7-15
-------
a)
MAIZE MODEL YIELDS:
DRYLAND
b)
38-40 N
36-38 N
LATITUDE
34-36 N
<34 N
SE 1951-1980
G'SS 2 X C02
FD- 2 x CC2
MAIZE MODEL YIELDS:
AUTOMATIC IRRIGATION
40-42 N 38-40 N
36-38 N
LATITUDE
34-36 N
<34 N
1951-1980
3IS5 2 x C02 I ! G~DL 2
Figure 7-5.
CERES-Maize yields with climate change and direct
C02 effect: (a) dryland (b) irrigated
Source: Rosenzweig, Volume .
7-16
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Chapter 7
climate change into economic consequences (see Chapter 10,
Agriculture, for study design and limitations). Analyses were
done both for climate change alone and for the combined effects
of climate change and enhanced C02 concentrations. This analysis
did not address the issues of whether the physical and
institutional changes required to accommodate increased demand
for irrigated acreage are feasible.
Regional Results
The estimates of Adams et al. (see Volume _) for total
agricultural and irrigated acreage changes in the southern Great
Plains States (Oklahoma and Texas only) are shown in Table 7-4.
Agricultural land decreases in the southern Great Plains in all
scenarios, both GISS and GFDL with and without the direct effects
of C02. Decreases range from -22 to, -4%. Irrigated acreage on
the other hand increases in all scenarios, from 9 to'30%. This
is because of increased stability in irrigated yields relative to
dryland yields and a rise in commodity prices that makes
expansion of irrigation production economically feasible. The
higher limits of these ranges indicate the possibility of
significant changes in the agriculture of the region.
Regional Implications
The results of the agricultural economics study imply that
wheat and corn production may shift away from the southern Great
Plains, causing dislocations of rural populations. For many
rural communities in the region, this may further weaken an
economic base already under pressure from long-term structural
changes in U.S. agriculture.
If irrigated acreage does increase in the area, groundwater
overdrafts also would be likely, along with associated increases
in surface and groundwater pollution and other forms of
environmental degradation.
Demand for Water for Irrigation
The projected higher air temperatures due to the growth of
trace gases in the atmosphere may increase evaporative demands.
Crop water use and irrigation water requirements are governed
largely by the evaporation process.
Study Design
Allen and Gichuki (see Volume _) evaluated the effects of
climate change and variations in canopy resistance on crop
irrigation water requirements in the Great Plains. Allen and
7-17
-------
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Chapter 7
Gichuki used a soil water balance-evapotranspiration model to
calculate daily soil moisture balances, evapotranspiration, and
irrigation water requirements. The model employed the Penman-
Monteith combination method to estimate crop evapotranspiration
for corn, wheat, and alfalfa (Monteith, 1965). The model was run
for four levels of potential direct effects of CO2 on
transpiration.
Limitations
Air temperature data at airport locations were adjusted to
reflect temperature profiles to be expected over an irrigated
crop field. This study assumed that alfalfa, corn, and wheat all
would respond similarly to increased C02 (which may reduce
transpiration), although published reports of experimental
results show different responses among crops (see Rose, Volume
_)
Results
The results .indicate that irrigation requirements may
increase or decrease, depending on the type of crop, changes in
climatic factors and variations in canopy resistance. The
perennial crop alfalfa showed persistent increases in seasonal
net irrigation water requirements (see Figure 7-6). These
increases were driven primarily by higher temperatures, with less
influence from stronger winds, greater solar radiation, and a
longer growing season.
On the other hand, decreases in seasonal net irrigation
requirements were predicted for winter wheat and corn in most
regions, depending on the projected direct effects of COj on
transpiration. These modeled decreases were generally due to
shorter seasons caused by higher temperatures, which accelerates
crop life cycles. When crop varieties appropriate to the longer
growing season were modeled, irrigation requirements for winter
wheat increased. Irrigation water requirements during peak
periods increased in almost all cases (Figure 7-7).
Plant canopy (leaf) temperatures were predicted to increase
above current baseline values for all crops and sites studied.
Projected increases in leaf temperatures may reduce
photosynthetic activity and crop yields. (See discussion on
direct effects of CO2 in Chapter 10, Agriculture.)
7-19
-------
120
100
SO
60
4O
20
NE-QSS KS-QSS OK-QSS TX-QSS
NE-GFDL KS-GFDL OK-GFDL TX-GRX
Figure 7-6. Seasonal irrigational requirement for 20% increase
in bulk stomatal resistance of alfalfa.
Source: Allen and Gichuki, Volume .
7-20
-------
10O
Y//////////A
4CK
ssssssssssss
GOT.
V//////////A
100
(C) WINTER WHEAT
-20
Figure 7-7,
Percent change in net peak monthly irrigation
requirement from baseline values for alfalfa, corn
and winter wheat vs. postulated increases in bulk
stomatal diffusion resistance.
Source: Allen and Gichuki, Volume
7-21
-------
Great Plains
Implications
Any reduction in irrigation requirements for corn and winter
wheat would be beneficial because less water and energy would be
required to produce the crops. However, the shortened crop
durations might allow for longer-season varieties or double-
cropping (planting two crops in one season), increasing total
irrigation requirements.
Expanded farm irrigation systems may require increased
capital investments and larger peak drafts on groundwater systems
and on energy supplies. Increased groundwater extraction would
pose serious environmental and economic problems, especially
where "water mining" is currently a major problem. Any increases
in irrigation efficiency by irrigators as an attempt to cope with
projected water shortages may lead to increased salinity problems
if leaching requirements are not met.
Water Quality
Agricultural pesticides are a high-priority pollution
problem in at least half of the States within the U.S. Great
Plains and Central Prairie. How the movements of agricultural
chemicals may be affected by climate change is essential to a
thorough evaluation of potential changes in drinking water
quality.
Study Design
Johnson et al. used the Pesticide Root Zone Model (PRZM) to
(Carsel et al., 1984) to simulate the partitioning of pesticides
between plant uptake, chemical degradation, surface runoff,
surface erosion, and soil leaching in the Great Plains under
baseline climate and climate change scenarios. The locations
modeled were representative of cropping practices for winter
wheat and cotton in the region. (See the national agriculture
chapter of this report for further discussion of the study's
design and limitations.)
Results
As Figure 7-8 shows, in the winter wheat regions of the
central Great Plains, surface runoff and surface erosion increase
under the GISS scenario, and results are mixed in the GFDL
scenario. In the southern Great Plains cotton simulations, the
GISS and GFDL scenarios produced increases in surface pesticide
losses with runoff and eroded soils.
7-22
-------
of Base 100.
PRZM Modeled Impacts of 2XC02 on
Pesticide Runoff Losses
winter wmut cotton
crop region
PflZM Modeled Impacts of 2xC02 on
Pesticide Erosion Losses
winter *i««t cotton
crop region
100T
X of Base
PRZM Modeled Impacts of 2XC02 on
Pesticide Leaching
xlntcr wheat cotton
crop region
Figure 7-8. Regional summary of surface and subsurface
pesticide loss as a percentage of the base climate
scenario losses.
Source: Johnson et al., Volume
7-23
-------
Great Plains
The quantity of pesticides leached below the crop root zone
is estimated to decrease everywhere except perhaps on silty soils
in the cotton region. This overall decline most likely results
from higher evaporative demands in response to temperature
increases and less moisture available for infiltration and deep
percolation.
Implications
Results of the modeling imply that water quality in the
Southern Great Plains may be affected by climate change. Surface
water appears to be vulnerable to deterioration under climate
change conditions, although the result does not hold for all
cases. Groundwater quality appears to be less at risk than
surface water quality. However, because these results are highly
dependent on the frequency and intensity of precipitation events,
directions of change are uncertain.
Livestock
Livestock production is a critical agricultural activity in
the Great Plains. Since the approximately 8 million head of beef
cattle in Texas represent nearly 40% of all beef cattle in the
United States, climate change factors that affect Texas cattle
will affect beef production nationally.
The warming predicted in the climate change scenarios may
alleviate cold stress conditions in the winter but will most
likely exacerbate heat stress in the summer. Warmer summers may
necessitate more hours of indoor cooling. Reproductive
capabilities may also decline because of higher temperatures.
(See the Agriculture chapter in this report for a discussion of
livestock issues.) Higher temperatures also may enable tropical
diseases to extend their ranges into the Great Plains. High
temperatures may also reduce insect pest activities in some
locations and increase them in others.
Energy
Linder and Inglis estimated the national changes in demand
for electricity for the years 2010 and 2055. (See the Energy
chapter of this report for a further description of study's
design and methodology.) They first estimated the change in
electricity demand due to projected growth in GNP and population,
and then factored in changes in demand based on the GISS
transient climate change scenarios A and B. The results for the
southern and central Great Plains are discussed here.
7-24
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Chapter 7
Table 7-5. Estimated Change in Peak Demand and Annual Energy
Requirements Induced by Climate Change (%)
2010
Utility Area
Kansas/Nebraska
Oklahoma
Texas, east
Texas , south
Texas , west
GISS
Ann.
1.7
3.0
3.0
3.3
3.1
A
Peak
6.8
7.9
7.9
10.0
8.6
GISS
Ann.
1.3
2.8
2.8
1.7
2.4
B
Peak
5.2
6.6
6.6
5.1
6.1
2055
GISS
Ann.
5.7
11.3
11.3
10.6
11.1
A
Peak
22.1
25.3
25.3
24.6
25.1
Source: Linder and Inglis, Volume .
7-25
-------
Great Plains
Results
Estimates of changes in peak demand, capacity requirements, and
cumulative and annual costs projected for the climate change
scenarios are shown in Table 7-5. New capacity requirements are
estimated to increase by 15-28% by 2010 for the climate change
scenarios compared to the base case. By 2010, cumulative capital
costs induced by climate change may grow by $3.7-6.7 billion, and
annual costs may rise by 3-6%.
In 2055, new capacity generating requirements are estimated to
increase by 22 to 45 gigawatts or 27-39%. Power generation in
the region increased by about 10-14% under the climate change
scenarios.
Linder calculated that cumulative capital costs for energy in
the region would increase by $20-53 billion with climate change.
The estimated changes in annual costs induced by climate
change range from $5 to 10 billion nearly the same as the $11
billion difference in high and low GNP estimate.
Implications
Increased energy capacity requirements and the need to
maintain the reliability of utility systems could place
additional stress on the Great Plains. Power plants may take the
cooling water they need from rivers or from the already overused
Ogallala Aquifer. Fossil fuel plants could add more pollutants
to the air.
POLICY IMPLICATIONS
Policymakers may have to respond to a decline of
agricultural production in the area, increased demand for water,
and poorer water quality. The major issues for policymakers to
address include land-use management, water resource management,
water quality regulations, and risk management (see Riebsame,
Volume _). Regional utility planners and policymakers should
also begin to consider climate change as a factor along with
other uncertainties affecting their resource availability
analyses and planning decisions.
Land-Use Management
State land managers should analyze how their missions and
holdings may be affected by climate change and should develop
flexible strategies to deal with potential impacts. Federal
agencies, such as the Department of Agriculture, the Forest
7-26
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Chapter 7
Service, the Fish and Wildlife Service, and the Department of
Interior, should work with State agriculture, forest, and park
agencies on such plans.
Agriculture and other uses may shift across several States.
This adjustment process can be made more efficient and less
disruptive if individual jurisdictions, such as municipalities,
States, and federal regions respond in a coordinated manner.
Decisions made by managers of agriculture will affect decisions
on forests, wildlife, water resources, and other areas.
Decisionmakers should work together on developing sound and
flexible anticipatory strategies, and new institutional
arrangements may be needed.
Some programs already in place can help to lessen the
negative effects of climate change on the Great Plains. Federal
legislation such as the "Sod-Buster Bill" and the related "Swamp-
Buster Bill," and the Conservation Reserve Program, are examples
of new policies designed to reduce the use of marginal lands for
agriculture. These laws have the basic goals of protecting the
most erodible farmlands by removing them from crop production and
of using conservation as a tool for reducing overproduction.
These policies are prudent now for reducing runoff and erosion,
and may become even more important for protecting water quality
in light of climate change. Protection of marginal lands may
have to be weighed against the need for greater crop production
if climate change lowers yields.
Water Resource Management
With climate change, parts of the Great Plains are likely to
suffer increasing aridity. Farmers may demand more water for
irrigation, although groundwater sources are already taxed.
Competition for water resources between agricultural and
nonagricultural demands may be exacerbated. Managers need to
factor these potential effects of climate change into their
decisions on irrigation, drainage, and water transfer systems and
as they formulate supply allocation rules, reservoir operating
criteria, safety protocols, and plans for long-term water
development. Water conservation techniques, water reallocation
between competing uses, water transfers and markets, and land-use
adjustments must be evaluated for their ability to absorb the
effects of future climate change. Primary consideration should
be given to environmentally sound programs for managing water
resources.
7-27
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Great Plains
Water Quality Regulations
Decisionmakers should consider the potential effects of
climate change on water quality and the use of pesticides. They
should examine alternative pest control strategies, such as
Integrated Pest Management, which uses such techniques as
biological control, genetic resistance, and innovative cropping
systems to reduce pesticide applications.
Risk Management
Several government, semi-private and private institutions
have a large financial stake in Great Plains agriculture through
land credit, commodity and equipment loans, and insurance.
Additionally, the federal government provides disaster relief for
climate extremes affecting regional agriculture. Climate warming
poses a potential long-term risk to the financial institutions
supporting agriculture, the resources available for emergency
relief, and to individual farmers. This consideration should be
carefully assessed and the risk monitored as climate changes.
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Chapter 7
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USEPA/ERL Report EPA-600-3-84-109. Washington, DC: U.S.
Government Printing Office.
Glantz, M.H., and Ausubel, J.H. 1984. The Ogallala Aquifer and
carbon dioxide: Comparison and convergence. Environ. Conser.
11(2):123-31.
High Plains Associates. 1982. Six-State High Plains-Ogallala
Aquifer Regional Resources Study. Austin, Texas.
Hurt, R.D. 1981. The Dust Bowl. Chicago: Nelson-Hall.
Jones, C.A., and J.R. Kiniry. 1986. CERES-Maize: A Simulation
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A&M Press.
Liverman, D.M., W.H. Terjung, J.T. Hayes, and L.O. Mearns. 1986.
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Lockeretz, W. 1978. The lessons of the Dust Bowl. American
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Monteith, J.L. 1965. Radiation and crops. Experimental
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Great Plains
Robertson, T., V.W. Benson, J.R. Williams, C.A. Jones, and J.R.
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