United States
Environmental Protection
Agency
Office of Policy
(2111)
EPA 236-F-98-007X
September 1998
Climate Change And South Dakota
The earth's climate is predicted to change because human
activities are altering the chemical composition of the atmosphere
through the buildup of greenhouse gases — primarily carbon
dioxide, methane, nitrous oxide, and chlorofluorocarbons. The
heat-trapping property of these greenhouse gases is undisputed.
Although there is uncertainty about exactly how and when the
earth's climate will respond to enhanced concentrations of
greenhouse gases, observations indicate that detectable changes
are underway. There most likely will be increases in temperature
and changes in precipitation, soil moisture, and sea level, which
could have adverse effects on many ecological systems, as well
as on human health and the economy.
The Climate System
Energy from the sun drives the earth's weather and climate.
Atmospheric greenhouse gases (water vapor, carbon dioxide,
and other gases) trap some of the energy from the sun, creating
a natural "greenhouse effect." Without this effect, temperatures
would be much lower than they are now, and life as known today
would not be possible. Instead, thanks to greenhouse gases, the
earth's average temperature is a more hospitable 60°F. However,
problems arise when the greenhouse effect is enhanced by
human-generated emissions of greenhouse gases.
Global warming would do more than add a few degrees to today's
average temperatures. Cold spells still would occur in winter, but
heat waves would be more common. Some places would be drier,
others wetter. Perhaps more important, more precipitation may
come in short, intense bursts (e.g., more than 2 inches of rain
in a day), which could lead to more flooding. Sea levels would
be higher than they would have been without global warming,
although the actual changes may vary from place to place
because coastal lands are themselves sinking or rising.
The Greenhouse Effect
Some solar radiation
is reflected by the
earth and the
atmosphere
Some of the infrared radiation passes
through the atmosphere, and some is
absorbed and re-emitted in all directions
by greenhouse gas molecules. The effect
of this is to warm the earth's surface and
the lower atmosphere.
Source: U.S. Department of State (1992)
Emissions Of Greenhouse Gases
Since the beginning of the industrial revolution, human activities
have been adding measurably to natural background levels of
greenhouse gases. The burning of fossil fuels — coal, oil, and
natural gas — for energy is the primary source of emissions.
Energy burned to run cars and trucks, heat homes and busi-
nesses, and power factories is responsible for about 80% of
global carbon dioxide emissions, about 25% of U. S. methane
emissions, and about 20% of global nitrous oxide emissions.
Increased agriculture and deforestation, landfills, and industrial
production and mining also contribute a significant share of
emissions. In 1994, the United States emitted about one-fifth of
total global greenhouse gases.
Concentrations Of Greenhouse Gases
Since the pre-industrial era, atmospheric concentrations of carbon
dioxide have increased nearly 30%, methane concentrations have
more than doubled, and nitrous oxide concentrations have risen
by about 15%. These increases have enhanced the heat-trapping
capability of the earth's atmosphere. Sulfate aerosols, a common
air pollutant, cool the atmosphere by reflecting incoming solar
radiation. However, sulfates are short-lived and vary regionally,
so they do not offset greenhouse gas warming.
Although many greenhouse gases already are present in the
atmosphere, oceans, and vegetation, their concentrations in the
future will depend in part on present and future emissions.
Estimating future emissions is difficult, because they will depend
on demographic, economic, technological, policy, and institu-
tional developments. Several emissions scenarios have been
developed based on differing projections of these underlying
factors. Forexample, by 2100, in the absence of emissions control
policies, carbon dioxide concentrations are projected to be 30-
150% higher than today's levels.
Current Climatic Changes
Global mean surface temperatures have increased 0.6-1.2°F
between 1890 and 1996. The 9 warmestyears in this century all
have occurred in the last 14 years. Of these, 1995 was the warmest
year on record, suggesting the atmosphere has rebounded from
the temporary cooling caused by the eruption of Mt. Pinatubo in
the Philippines.
Several pieces of additional evidence consistent with warming,
such as a decrease in Northern Hemisphere snow cover, a
decrease in Arctic Sea ice, and continued melting of alpine
glaciers, have been corroborated. Globally, sea levels have risen
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Global Temperature Changes (1861-1996)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
Year
Source: IPCC (1995), updated
4-10 inches over the past century, and precipitation over land has
increased slightly. The frequency of extreme rainfall events also
has increased throughout much of the United States.
A new international scientific assessment by the Intergovern-
mental Panel on Climate Change recently concluded that "the
balance of evidence suggests a discernible human influence
on global climate."
Future Climatic Changes
For a given concentration of greenhouse gases, the resulting
increase in the atmosphere's heat-trapping ability can be pre-
dicted with precision, but the resulting impact on climate is more
uncertain. The climate system is complex and dynamic, with
constant interaction between the atmosphere, land, ice, and
oceans. Further, humans have never experienced such a rapid rise
in greenhouse gases. In effect, a large and uncontrolled planet-
wide experiment is being conducted.
General circulation models are complex computer simulations that
describe the circulation of air and ocean currents and how energy
is transported within the climate system. While uncertainties
remain, these models are a powerful tool for studying climate. As
a result of continuous model improvements over the last few
decades, scientists are reasonably confident about the link
between global greenhouse gas concentrations and temperature
and about the ability of models to characterize future climate at
continental scales.
Recent model calculations suggest that the global surface temper-
ature could increase an average of 1.6-6.3°F by 2100, with signif-
icant regional variation. These temperature changes would be far
greater than recent natural fluctuations, and they would occur
significantly faster than any known changes in the last 10,000
years. The United States is projected to warm more than the
global average, especially as fewer sulfate aerosols are produced.
The models suggest that the rate of evaporation will increase as
the climate warms, which will increase average global precipita-
tion. They also suggest increased frequency of intense rainfall as
well as a marked decrease in soil moisture over some mid-
continental regions during the summer. Sea level is projected to
increase by 6-38 inches by 2100.
Calculations of regional climate change are much less reliable
than global ones, and it is unclear whether regional climate will
become more variable. The frequency and intensity of some
extreme weather of critical importance to ecological systems
(droughts, floods, frosts, cloudiness, the frequency of hot or cold
spells, and the intensity of associated fire and pest outbreaks)
could increase.
Local Climate Changes
Over the last century, the average temperature in Pierre, South
Dakota, has increased 1.6°F, and precipitation has increased by
up to 20% in many parts of the state. These past trends may or
may not continue into the future.
Over the next century, climate in South Dakota may change even
more. For example, based on projections made by the Intergov-
ernmental Panel on Climate Change and results from the United
KingdomHadley Centre's climate model (HadCM2), a model that
accounts for both greenhouse gases and aerosols, by 2100
temperatures in South Dakota could increase by 3°F in spring and
summer (with a range of 1 -6°F) and 4°F in fall and winter (with a
range of 2-7°F). Precipitation is estimated to increase by 10%
(with a range of 5 -20%) in spring, summer, and fall, and 20% in
winter (with a range of 10-40%). The amount of precipitation on
extreme wet or snowy days in winter is likely to increase. Other
climate models may show different results, especially regarding
estimated changes in precipitation. The impacts described in the
sections that follow take into account estimates from different
models. The frequency of extreme hot days in summer would
increase because of the general warming trend. It is not clear how
the severity of storms might be affected, although an increase in
the frequency and intensity of winter storms is possible.
Human Health
Higher temperatures and increased frequency of heat waves may
increase the number of heat-related deaths and the incidence of
heat-related illnesses. South Dakota, with its irregular, intense
Precipitation Trends From 1900 To Present
Trends/100 years
+20%
+10%
+5%
-5% O
-10% O
-20%
Source: Karl et al. (1996)
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heat waves, could be susceptible. These effects have been
studied only for populations living in urban areas; however, even
those in rural areas may be at risk. South Dakota lacks large cities.
which are most sensitive to heat waves; however, Minneapolis
will experience similar changes in climate and could indicate how
populations in South Dakota cities might be affected. One study
estimates that in Minneapolis a summer warming of 5°F could
increase heat-related deaths by threefold from about 60 to 180
(although increased air conditioning use may not have been fully
accounted for). The elderly, especially those living alone, are at
greatest risk. This study also projects little change in winter-
related deaths in South Dakota.
Climate change could increase concentrations of ground-level
ozone. For example, high temperatures, strong sunlight, and
stable air masses tend to increase urban ozone levels. A 2°F
warming in the Midwest, with no other change in weather or
emissions, could increase concentrations of ozone, a major
component of smog, by as much as 8%. Although South Dakota
is in compliance with current air quality standards, increased
temperatures could make remaining in compliance more difficult.
Ground-level ozone is associated with respiratory illnesses such
as asthma, reduced lung function, and respiratory inflammation.
Air pollution also is made worse by increases in natural hydro-
carbon emissions such as emissions of terpenes by trees and
shrubs during hot weather. If a warmed climate causes increased
use of air conditioners, air pollutant emissions from power plants
also will increase.
Upper and lower respiratory allergies are influenced by humidity.
A 2°F warming and wetter conditions could increase respiratory
allergies.
Warming and other climate changes could expand the habitat
and infectivity of disease-carrying insects. Infected individuals
can bring malaria to places where it does not occur naturally.
Also, some mosquitoes in South Dakota can carry malaria, and
some can carry western equine encephalitis, which can be lethal
or cause neurological damage. If conditions become warmer and
wetter, mosquito populations could increase, thus increasing the
risk of transmission if these diseases are introduced into the area.
Warmer temperatures could increase the incidence of Lyme
disease and other tick-borne diseases in South Dakota, because
populations of ticks, and their rodent hosts, could increase under
warmer temperatures and increased vegetation. Increased runoff
from heavy rainfall could increase water-borne diseases such as
giardia, cryptosporidia, and viral and bacterial gastroenteritides.
Developed countries such as the United States should be able to
minimize the impacts of these diseases through existing disease
prevention and control methods.
Agriculture
The mix of crop and livestock production in a state is influenced
by climatic conditions and water availability. As climate warms.
production patterns could shift northward. Increases in climate
variability could make adaptation by farmers more difficult.
Warmer climates and less soil moisture due to increased evapora-
tion may increase the need for irrigation. However, these same
Changes In Agricultural Yield And Production
Dryland Yield Production
Corn Wheat Hay Corn Wheat Hay
• AT = 9°F; Aprecip. = 7% • AT = 8°F; Aprecip. = 9%
Sources: Mendelsohn and Neumann (in press); McCarl (per-
sonal communication)
conditions could decrease water supplies, which also may be
needed by natural ecosystems, urban populations, industry, and
other users.
Understandably, most studies have not fully accounted for
changes in climate variability, water availability, crop pests.
changes in air pollution such as ozone, and adaptation by farmers
to changing climate. Including these factors could change
modeling results substantially. Analyses that assume changes in
average climate and effective adaptation by farmers suggest that
aggregate U.S. food production would not be harmed, although
there may be significant regional changes.
In South Dakota, production agriculture is a $3.3 billion annual
industry, two-thirds of which comes from livestock, mainly cattle.
Very few of the farmed acres are irrigated. The major crops in the
state are corn, wheat, and hay. Corn and wheat yields could rise
by 3 5 -51 %, while hay and pasture yields could remain un-
changed. Farmed acres in the state could increase by about 30%.
Livestock and dairy production may not be affected, unless
summer temperatures rise significantly and conditions become
significantly drier. Under these conditions, livestock tend to gain
less weight and pasture yields decline, limiting forage.
Water Resources
The major river in South Dakota is the Missouri River, which
drains almost the entire state. South Dakota is primarily rural, and
agriculture is the dominant user of water. The area west of the
Missouri, where ranching predominates, principally uses surface
water. The area east of the Missouri, which has a farming-based
economy, relies heavily on groundwater. Streamflow is highly
variable in South Dakota. Except for the Missouri, which has a
sustained flow and large storage reservoirs, many streams do not
provide a dependable water supply. Particularly in the eastern
part of the state, streams are characterized by high flows during
the spring and early summer that can cause flooding and by low
flows during the summer, fall, and winter that can limit uses. In a
warmer climate, this situation could be exacerbated. Warmer
winter temperatures would lead to earlier spring snowmelt.
resulting in higher streamflows in winter and spring. In the
summer, without large increases in precipitation, higher tempera-
tures and increased evaporation would further reduce
streamflows
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and lake levels. For a doubling in CO2 levels, some studies show a
6-34% reduction in inflow into the Missouri River system.
Groundwater levels also could be reduced by lower spring and
summer recharge. Although many water control projects have
been built to alleviate South Dakota's water shortages, the water
demands of the increasing population, mining operations.
irrigation, and energy-development activities continue to grow.
Lower streamflows and groundwater levels would limit water
availability for irrigation, hydropower generation, fish and wildlife
habitat, recreation, and water supplies for municipalities, indus-
tries, and rural areas. South Dakota is susceptible to periodic
droughts that severely damage the state's agriculture-based
economy. Droughts could occur more frequently in a warmer
climate. Higher summer temperatures and lower flows also could
degrade water quality by concentrating pollutants and reducing
the capacity of streams to assimilate wastes. Prairie pothole
wetlands, which provide important waterfowl habitat, also would
be impaired by declining water levels.
More rain is possible with a warmer climate. Although this could
alleviate water shortages, it also could increase flooding. Prairie
streams such as the Big Sioux and James rivers in the eastern part
of the state do flood agricultural lands. Additionally, in a warmer
climate, heavier rains are expected, which could increase flash
floods in the western part of the state. Increased rainfall also
could increase erosion and exacerbate levels of pesticides
and fertilizers in runoff from agricultural lands and exacerbate
water quality problems associated with nutrient enrichment
and sedimentation of streams and lakes.
Forests
Trees and forests are adapted to specific climate conditions.
and as climate warms, forests will change. These changes could
include changes in species composition, geographic range, and
health and productivity. If conditions also become drier, the
current range and density of forests could be reduced and
replaced by grasslands and pasture. Even a warmer and wetter
climate could lead to changes; trees that are better adapted to
warmer conditions, such as oaks and pines, would prevail. Under
these conditions, forests could become more dense. These
changes could occur during the lifetimes of today's children.
particularly if the change is accelerated by other stresses such as
fire, pests, and diseases. Some of these stresses would them-
selves be worsened by a warmer and drier climate.
With changes in climate, the extent of the few forested areas in
South Dakota could change. The extent and direction of change
depends on many factors, including whether soils become drier
and, if so, how much drier. Hotter, drier weather could increase the
frequency and intensity of wildfires, decreasing the range and
density of ponderosa pines, especially in the Black Hills. Grass-
lands and savanna eventually could replace many of the forests
and riparian woodlands in South Dakota. However, some studies
indicate increases in rainfall, particularly in the northeastern part
of the state, could lead to increases in the extent and character of
shrub and woodland areas.
Changes In Forest Cover
Current +10°F, +13% Precipitation
Broadleaf Forest
Savanna/Woodland
Shrub/Woodland
Grassland
Sources: VEMAP Participants (1995); Neilson (1995)
Ecosystems
South Dakota is a mosaic of terrestrial and aquatic habitats
important for both resident and migratory wildlife species.
Historical ecosystems included mixed grass plains, tallgrass
transition areas, tallgrass prairie, and wooded areas. Construction
of dams and channels along the Missouri River has altered or
eliminated riparian habitats. Of an original 500 miles of riparian
bottomland timber along the Missouri River, less than 80 miles
remain. These alterations have directly affected the breeding
habitat of the piping plover, interior least tern, and whooping
crane, and the wintering habitat of the bald eagle. Spawning
habitats and movements of the pallid sturgeon, paddlefish,
sturgeon chub, sicklefin chub, and finescale dace have been
drastically altered or eliminated. Conversion of native prairie to
agricultural use is a second major cause of habitat loss or
alteration in the state. It is estimated that more than 75% of the
land in eastern South Dakota is under cultivation. Wetlands have
been drained, eliminating habitat for fish and wetland-dependent
birds, mammals, reptiles, amphibians, and insects. Changes in
climate can be expected to further stress ecosystems and wildlife
such as the mountain lion, black bear, longnose sucker, fringe-
tailed myotis, marten, and bald eagle.
Based on model projections, national wildlife refuges in South
Dakota appear to be among the most vulnerable in the United
States to changes in climate. The region's national wildlife
refuges and prairie pothole systems appear to be especially
sensitive to changes in precipitation and temperature. Sixty
percent of the annual variation in the number of these wetlands
can be explained by year-to-year changes in temperature and
precipitation. Smaller wetlands may be particularly vulnerable to
climate change. Projections show that warmer annual tempera-
tures affect wetlands by reducing open water and increasing
vegetation cover, independent of precipitation. Rising tempera-
tures, if continued for several years, may decrease breeding bird
density and diversity in this critically important waterfowl habitat.
Major additional threats to ecosystems include habitat loss and
species extinction, increased fire frequency, and
increased vulnerability to invasive plant and insect species.
For further information about the potential impacts of climate
change, contact the Climate and Policy Assessment Division
(2174), U.S. EPA, 401 M Street SW, Washington, DC 20460, or
visit http://www. epa.gov/globalwarming/impacts.
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