United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth IN/IN 55804
Research and Development
EPA-600/S3-84-051 May 1984
Project Summary
Changes in Terrestrial Ecology
Related to a Coal-Fired Power
Plant: Wisconsin Power Plant
Impact Study
Daniel E. Willard, William W. Jones, and Jay Benforado
The full report summarizes the eco-
logical effects on terrestrial plants and
animals from a 1054-MW coal-fired
power plant. Research was conducted
from 1971 through 1977 at the site of
the Columbia Generating Station, in the
eastern flood-plain of the Wisconsin
River in south central Wisconsin.
Initial studies were largely descriptive,
involving development of species lists
and documentation of habitats. Mapping
of plant communities documented
extensive changes, most notably heavy
losses of sedge meadow habitats and
increases in open water. These impacts
on plant communities brought about
concomitant changes in animal com-
munities.
Bird populations were observed and
analyzed in a sampling system consisting
of five permanent transects, each
having 17 or 18 stations and representing
the entire range of plant communities.
In mean analysis, a "t" test was applied
to identify significant differences in the
mean number of birds observed in each
station during each year of study. The
Shannon-Weaver function, which com-
bines species richness and evenness
components into a single index, was
used as a measure of diversity. Polar
ordination, a type of multivariate
analysis based on a similarity coefficient
to measure "distances" between sta-
tions, revealed many changes in the
composition and structure of bird
communities. Observations of a nesting
colony of great blue herons showed that
the nesting population decreased and
foraging habits changed as a result of
the impact of the cooling lake on the
wetlands.
Drift fence-pitfall trapping is one
source of information on presence and
abundance of species, migration routes
and seasonal use of different habitats,
and occurrence of rare and endangered
species. This report summarizes the
effects of drift fence construction and
orientation, trap dimensions, cycles in
time, and weather variables on the
results obtained by drift fence-pitfall
trapping.
This Project Summary was developed
by EPA 's Environmental Research
Laboratory, Duluth, MN, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
This report summarizes several studies
on the effects of a 1054-MW coal-fired
power plant on terrestrial plants and
animals. The studies were conducted
from 1971 through 1977 at the site of the
Columbia Generating Station near Portage,
Wisconsin, in the eastern floodplam of
the Wisconsin River. Before construction
began, the dominant vegetation of the
area was sedge meadow and -lowland
forest Building and operating the power
plant had major consequences for the
surrounding communities of plants and
animals.
Approach
The initial studies were primarily
descriptive. They involved developing
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lists of species, evaluating habitats, and
documenting elements in the natural
history of important species. For popula-
tion studies, field censuses were made
on a regular basis, using visual and
acoustical observations, traps, and nets
to assess densities of animal populations.
At the community level, plant communities
and habitat types were mapped and
analyzed by aerial photography, point-
quarter, and transect methods. Finally,
analytic studies were made to determine
the physiological and behavioral responses
to the impact of the power plant This
variety of approaches to impact analysis
provided a balance between long-term
qualitative observations and short-term
quantitative studies.
Studies of Plant Communities
Studies of plant communities are
important both in their own right and in
relation to animal studies, because
impacts on animal populations must be
understood in terms of any habitat
changes. Eighteen natural plant com-
munities were identified, described, and
mapped Table 1 summarizes changes in
the sizes of plant communities between
1971 and 1979. The net loss of 638 ha
represents the area occupied by the
generating station and its associated
facilities Four plant communities disap-
peared completely, while heavy losses
were sustained by the sedge meadow
community 1
Descriptive Animal Studies
Some 287 species of vertebrates use
the Columbia Generating Station site
This total is distributed as follows among
the classes of vertebrates-
Fishes 22
Reptiles and amphibians 32
Birds 197
Mammals 36
Usage by some species (e.g., geese,
warblers, walleyes) is seasonal, and some
of the animals are rare (muskellunge,
sandhill cranes, otter). Many species are
seasonally very abundant (red-winged
blackbirds, muskrats, chorus frogs,
walleyes). The site contains a number of
game species (ducks, white-tailed deer,
northern pike)
Although changes were observed m
many animal populations, determining
the significance of these changes was
difficult and identifying causal links was
sometimes impossible. The difficulty in
observing some animals, and the size of
the site made complete coverage difficult.
Long-term observations are needed to
distinguish natural fluctuations from
those induced by human activity. Finally,
Table 1. Changes in Size of Plant Communities (ha) from 1971 to 1979
Community type
Open water
Emergent Aquatics
Sedge Meadow
Shrub Car/-
Alder Thickets
Fen
Prairie
Southern Wet Forest
Southern Wet Mesic Forest
Southern Mesic Forest
Southern Dry Mesic Forest
Southern Dry Forest
Northern Wet Forest
Northern Wet Mesic Forest
Oak Barrens
Sand Communities
Cliff Face
Old Field
Total
Area
1971
236
358
662
34
12
6
7
137
270
15
93
70
2
3
19
23
18
81
2046
Area
1979
274
311
181
13
0
0
4
165
270
18
88
26
0
0
7
30
18
35
1408
Area lost
1971-197-9
47
68
481
28
12
6
3
63
0
1
18
54
2
3
12
4
0
71
Area gained
1971-1979
74
21
0
7
0
0
0
91
0
3
13
0
0
0
0
11
0
15
Net
change
+27
-47
-481
-21
-12
-6
-3
+28
0
+2
-5
-54
-2
-3
-12
+7
0
-56
-638
animals tend to move in response to their
needs, so that some areas which seem
but lightly used may in fact be temporary
refuges necessary for survival.
Mammals
Mammals were studied by direct
observation, winter tracks, box traps, drift
fences, dropping boards, den counts, and
records of trappers.
Estimates of deer populations show a
reduction from 80 to 100 in 1971 to
approximately 50 in 1977. Destruction of
habitat coupled with increased access for
hunters was probably the cause for this
decline
Based on an average of five muskrats
per den, populations of muskrats varied
from approximately 1000 in 1972 to 250
in 1973. Few dens were observed in
1976. Muskrats do not exhibit regular
population cycles common in some
smaller microtines but are sensitive to
changes in water level and other environ-
mental factors. Because of environmental
changes generally favorable for muskrats,
it is expected that populations will
increase.
Reptiles and Amphibians
Reptiles and amphibians were studied
by seining, netting and trapping; and by
direct observation (shed skins, road kills,
chance encounters, resting places, and
habitats).
All amphibian species seemed to be
reduced in numbers. Results for reptiles
were inconclusive due to sparsity of data.
Three species of turtle occupy waters
throughout the site and nest in several
onsite areas. The six-lined race runner,
an endangered species of lizard, may
have been lost through habitat destruc-
tion. Sightings of several species of
snakes (mostly road kills) were too
infrequent for any conclusions about
population trends. The garter snake
remains in wet areas throughout the site.
Birds
Birds were studied during regular
walks along a set of five transects,
through observation of confined habitats
such as the cooling lake, and by incidental
observation
The total of 197 species observed from
1973 to 1977 includes permanent
residents, seasonal residents, migratory
visitors, and species utilizing temporary
transitional habitats created by construc-
tion activities.
Effects of the cooling lake exceeded all
other impacts on birds Numerous
species dependent on the wetlands for
nesting or foraging were displaced when
the 200-ha lake was filled. Affected
species included the red-winged blackbird,
sora rail, Virginia rail, American bittern,
harrier, and great blue heron Sandhill
cranes, relatively intolerant of disturbance,
deserted adjacent wetland areas.
The new cooling lake, however, attracted
thousands of migratory birds. Twenty-
two species of waterfowl were observed
during the 1975 spring migration. These
included the double-crested cormorant,
an endangered species in Wisconsin.
Only 17 migrant species used the cooling
lake in 1976 Furthermore, although the
coot population increased sharply, num-
bers of nearly all other species were
reduced. The decrease in use of the
cooling lake by migratory waterfowl may
be due to changes in the temperature or
quality of the water, or to the generally
wet conditions which created ephemeral
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ponds on nearby lands that may have
attracted the birds. Additional studies of
the lake's use by migrating waterfowl are
recommended 2
Population and Community
Studies
Transect Counts and Analyses
of Bird Populations
The sampling system consisted of five
permanent transects, each having 17 or
18 observation stations 2500 m2 in size.
All major plant communities were
sampled open water, emergent aquatic,
sedge meadow, shrub carr, southern wet
forest, southern wet mesic forest,
southern dry forest/southern dry mesic
forest, sand barrens, and old field. In
addition, a number of stations represented
community edge types.
To obtain a sample count, an observer
walked for three minutes through a
station on its center line, using visual and
song cues to record all birds observed
within the boundaries of the station. Each
transect was sampled approximately
every 10 days from April to October and
every 20 days during the rest of the year,
from 1973 through 1976 Data were
analyzed by three methods: mean analysis,
a diversity index, and polar ordination.
Mean Analysis
In mean analysis, a "f'testwas applied
to identify significant differences in the
mean number of birds observed in each
station during each year of the study.
Mean analysis revealed many cases
where a specific construction activity was
followed by an immediate decrease in the
sample mean In several cases, the
activity resulted in total destruction of the
habitat and the mean remained depressed.
Where construction caused only partial
or temporary destruction of a habitat, the
mean tended to rebound. Stations inun-
dated by the cooling lake showed a
decrease in mean number of birds except
when occasional rafts of waterfowl
appeared
Diversity Index
Although there is no concensus on how
to measure diversity, species diversity is
generally thought to be associated with
the stability of a habitat. This study
employed the Shannon-Weaver function,
H', which uses information theory for
analysis of community organization,
combining richness and evenness com-
ponents into a single index of diversity.
The equation is.
IM
H' = - I ( *J In *',
i-1 T T
where
N=total number of species
T=total number of individuals
x,=number of individuals in the ith
species.
Although the diversity index was lower
for impacted stations in most habitats,
the decrease was usually small. More
significantly, diversity values tended to
decrease with time at impacted stations,
while diversity at nonimpacted stations
did not show this trend. The decrease in
H' was most marked in impacted sedge
meadow habitats where, following a peak
in H' during filling of the lake, values
dropped sharply. A similar decrease
occurred in impacted old field stations.
Values of H' are more closely related to
changes in species richness than to
changes in species abundance Thus,
while values for the sample mean may
bounce back following construction,
values for diversity do not Construction
activities therefore have a larger impact
at the community level than is indicated
by changes in species abundance alone.
Polar Ordination
Polar ordination, a type of multivariate
analysis, was used to study changes in
composition and structure of bird com-
munities through detection of patterns in
the data. This technique expresses
variation by measuring the distance
between each pair of stands with com-
munities by means of a dissimilarity
coefficient, equal to
1 - 2w
a + b
where
a=sum of abundance values of all spe-
cies in one stand
b=sum of abundance values of all spe-
cies in another stand
w=sum of abundance values that the
two stands have in common for each
species.
These differences are then used to place
stands on axes
For ordination studies, data were taken
from observations during June and July
(the breeding season) 1973 through
1976. The most common species (e.g.,
song sparrow, blue jays, red-winged
blackbirds) were relatively unaffected by
construction activities The dominance of
these species is evident in the ordination
plots, in which it overshadows the effects
of construction on rarer species and thus
decreases the separation of impacted vs.
nonimpacted stations. Nevertheless,
ordination studies revealed major changes
in bird communities at stations affected by
construction activities Many of these
changes could be related to alterations in
the water regime, with consequent
effects on plant communities.
Clearly, construction of the Columbia
Generating Station has had a major
impact on local bird communities. Impacts
range from immediate responses to
specific construction activities, to changes
in diversity and evenness in various
habitats, to alteration in overall commun-
ity composition One widespread result is
the proliferation of common species at
the expense of rarer ones. This can have
serious implications for community
productivity, stability, and succession
Effects on Great Blue Herons
A great blue heron nesting colony is
located about 2 km west of the wetlands
on the generating station site In 1974,
the colony contained 113 active nests at a
density of 94/ha. The herons foraged in
groups of up to 1 2, in the diked area of the
wetlands During the winter of 1974, the
dikes were joined and the cooling lake
was filled. Few herons were observed
foraging on the site during the following
summer, and the density of nests in the
colony dropped to 69/ha. In 1976, herons
again began foraging along the dikes, but
the nest density dropped to 33/ha. The
herons no longer foraged in groups, but
rather, fed individually along the dikes at
regularly maintained intervals of about
150m By 1977, the number of nests had
fallen to 16 (9/ha), even though the
nesting site itself was unchanged from its
preconstruction condition.
The response of great blue herons to
construction of the Columbia Generating
Station was clearly a response to impacts
on the feeding grounds ratherthan onthe
nesting site Although the cooling lake
contains abundant food, the distribution
of food and its availability to great blue
herons have changed With foraging
possible only in limited areas along the
lake shore, the herons changed from a
pattern of feeding in groups to one of
solitary feeding in individual territories.
With food supplies curtailed, the nesting
population dropped sharply.
Drift Fence-Pitfall Trapping for
Data on Populations of Small
Animals
Baseline studies of populations of
small animals are often concerned with
the presence and abundance of species,
migration routes and seasonal use of
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different habitats, and the occurrence of
rare or endangered species Drift fence
trapping can provide some of this
information.
This report summarizes the effects of
various factors on results obtained by
drift fence-pitfall trapping. The factors
include:
1. Construction of drift fences (sheet
material vs screen),
2 Size and shape of traps,
3. Orientation of drift fences (parallel
or perpendicular to habitat bounda-
ries),
4 Cycles in time (daily and seasonal),
and
5 Weather (e g., precipitation, cloud
cover, temperature, wind).
Trapping took place between June 11
and October31,1976. Daily visits to traps
insured sampling of populations without
undue mortality. Altogether, 1227 indivi-
duals representing 28 species of small
mammals, reptiles, andamphibianswere
captured (Table 2). The species composi-
tion of captured animals varied spatially
and temporally, with some species
captured throughout the study and others
captured discontmuously. It would be
desirable to collect data for an entire year,
to provide information on seasonal
changes in populations and their use of
various habitats.
In general, more amphibians were
caught on fences running parallel to land-
water boundaries, while more mammals
were caught on fences running perpendic-
ular to these boundaries. This is because
amphibians tend to travel toward or away
from water, and mammals tend to travel
parallel to water boundaries. With a
longer period for collecting data, observa-
tions on relationships between animal
captures and drift fence orientation could
provide information on migration routes
and changes in habitats with time
The study showed also that temperature
and moisture are important in controlling
movements of small animals, and that
there is interaction among weather
variables. The effect of weather on
trapping results could be incorporated
into a predictive model that would yield
overall population estimates from actual
numbers of animals captured under
specific weather conditions
Conclusions
Plant Communities
The construction of the Columbia
Generating Station resulted in the net
loss of 638 ha of native plant communities
on the 2046 ha site. The largest single
loss was in sedge meadow (481 ha). Four
minor communities (alder thicket, fen,
northern wet forest, and northern wet
mesic forest) were lost completely.
Seepage and upwellmg of cooling lake
water under the dikes is dislodging peat
mats which continues to affect the sedge
meadow community west of the cooling
lake.
Mammals
White-tailed deer populations on the site
declined with the onset of construction
due to increased hunting pressure.
Habitat destruction and plant facilities,
which tend to restrict deer movements
along the Wisconsin River, have continued
to keep deer populations depressed.
Increases in the amount and depth of
water in the sedge meadow should favor
muskrats but may limit the range of voles
and shrews.
Drift fence-pitfall trapping proved a
suitable method for capturing a variety of
small mammals, reptiles, and amphibians.
Capture rates depend on trap size and
shape, orientation, timing, and weather
conditions. The method was useful for
gathering baseline data.
Birds
Construction activities directly affected
bird abundance; however, if the habitat
destruction was modest, abundance
levels in the affected areas returned to
predisturbance levels with the completion
of the construction activity. In the sedge
meadow and old field communities,
construction activities kept species
abundance below preconstruction levels.
Species diversity indices generally
decreased over time in those sampling
stations impacted by construction activi-
ties. This suggests that construction
activities had a larger community level
impact than species abundance changes
alone indicated.
The disturbances on the site seemed to
favor the more common bird species over
the rarer ones. Species which declined in
number during the study period include
harriers, sandhill cranes, and great blue
herons. A great blue heron colony which
used the Columbia sedge meadow for
Table 2. Summary of Pitfall Trap Captures of Small Mammals. Reptiles, and Amphibians
Mammals
Sorex arcticus
Saddlebacked shrew
S cinereus
Cinereous shrew
B/arina brevicauda
Short tailed shrew
Microtus pennsylvanicus
Meadow vole
No. Reptiles
Ophisaurus attenautus
Western glass lizard
446
S tor en a dekayi
Dekay's snake
12 S occipitomaculata
Red-bellied snake
Thamnophis sirtalis
Eastern garter snake
No,
3
34
82
54
Amphibians
Bufo americanus
American toad
Rana ciamitans
Green frog
R pipiens
Leopard frog
R. sylvatica
Wood frog
No.
124
52
185
2
M. Ochrogaster
Prairie vole
Zapus hudsonius
Hudsonian jumping mouse
Peromyscus bairdi
Prairie deer mouse
P gracilis
Woodland deer mouse
Eutamias jacksoni
Wisconsin least chipmunk
79
44
Opheodrys vernalis
Smooth green snake
Heterodon platyrhmos
Eastern hognose snake
Chrysemys picta
Painted turtle
Emydndea blandingi
Blandmg's turtle
Graptemys geographica
Map turtle
Trionyx spmiferus
Spiny soft shell turtle
25
6
20
7
2
1
Pseudacns trisenata
Chorus frog
Hyla crueller
Spring peeper
H. versicolor
Grey tree frog
Ambystoma laterale
Blue-spotted salamander
A tigrinum
Tiger salamander
3
83
8
23
2
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feeding declined from 113 active nests in
1974 to 16 nests in 1977
Polar ordination was useful in consider-
ing how certain environmental param-
eters affect bird species distributions. The
results suggest that polar ordination
could be used to predict how changes in
these parameters might affect species
distribution and abundance.
Recommendations
The baseline data and, consequently,
the results of this study would have been
more useful had they been obtained
before construction began. Unfortunately,
the initial field sampling occurred after
the start of construction.
Methods have recently been developed
to provide before-and-after assessments
in a shorter time frame and at less cost
than the present study. Most notable of
these is the U.S Fish and Wildlife
Services Habitat Evaluation Procedures
(HEP). However, such methods are not
designed to consider impacts to rare
species or unique habitats. In these
cases, direct surveys and measurements
must be used.
Drift fence-pitfall trapping and transect
counts are two conventional methods
that can be easily and cheaply used to
gather baseline data. When conducted
over sufficient time, such methods
effectively monitor and document impacts
to terrestrial communities.
References
1. Bedford, B. and 0. Loucks, 1982,
Response of Carex-Dommated Wetlands
to Altered Temperatures and Flooding
Patterns, Water Resources Center,
University of Wisconsin, Madison, Wis-
consin, 135 p.
2. Jaeger, M J. Predicting Effects of an
Electric Station on Wetland Passerine
Birds, EPA-600/3-80-020, U.S. Environ-
mental Protection Agency, Duluth, Min-
nesota, 25 p.
D. E. Willard, W. W. Jones, and J, Benforado are with Institute of Environmental
Studies, University of Wisconsin, Madison, Wl 53706.
Gary E. Glass /s the EPA Project Officer (see below).
The complete report, entitled "Changes in Terrestrial Ecology Related to a Coal-
Fired Po wer Plant: Wisconsin Power Plant Impact Study," (Order No. PB 84-171
701; Cost: $13.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Duluth, MN 55804
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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