RESTORING CRANE HABITAT ALONG THE PLATTE RIVER OF NEBRASKA
Beverly J. Weddle
INTRODUCTION
Critical habitat for the migration of endangered whooping cranes and
90% of the world's population of lesser sandhill cranes is found in
the Big Bend region of Nebraska's Platte River and the nearby Rainwater
Basin. This region is also critical for 7 to 9 million ducks and geese,
over 200 other species of migratory birds, and endangered or threatened
plant, clam and fish species (Johnsgard, 1991; Farrar, 1992). The Platte River itself is formed in western Nebraska at
the confluence of the North Platte River from Wyoming and the South
Platte River of Colorado. Both of these rivers originate from snow melt
in the Rocky Mountains. Once formed, the Platte flows over 300 miles
eastward and empties into the Missouri River (Hadley et al., 1987). The
Big Bend region, located in south central Nebraska near Interstate 80,
stretches approximately 80 miles from Lexington to Grand Island.
For many migratory birds, the Big Bend region is like the narrowest
part of an hourglass. The widest portions of the hourglass are the
wintering and nesting grounds. In spring, coming from New Mexico, Texas,
Louisiana and other areas, birds of the Central Flyway converge for
several weeks in this small area in Nebraska before flying north to
nesting grounds spread across Canada, Alaska and Siberia. Among the bird
species dependent on the Big Bend region are migrating whooping and
sandhill cranes. Two major areas of concern for these cranes are: 1)
the loss of suitable roosting sites in the river due to encroaching
vegetation and 2) the loss of a dietary source as wet meadows adjacent
to the river are diminished due to agricultural practices. In both
cases, the concerns are very politically charged as they involve water
and land rights, and are affected by alterations in hydrology. This
paper looks at first, the loss of river roosting sites and attempts at
restoration or reclamation of those sites. The remainder of the paper
will be spent discussing the second concern - that of restoration
of wet meadows.
RIVER ROOSTING SITES
The Platte River was once a very broad, shallow braided river
characterized by shifting sandbars with little or no woody vegetation
within or near the river. The riparian zone was not forested, but rather
had extensive wet meadows (Williams, 1978). Cranes fed in the wet
meadows and roosted at night on the sandbars in the river. (Johnsgard,
1991). As settlement occurred in Colorado, Wyoming, and Nebraska, so did
diversion of water and damming of the river occur, particularly for
irrigation and hydroelectric power purposes. With this diversion and
damming of water, stream flows and sediment transport decreased
significantly in the Platte causing channelization of the river, and
growth of woody vegetation that could no longer be eliminated by the once
powerful scours of the streamflow and sand. This growth of woody
vegetation on islands in the river decreased roosting sites for cranes as
they choose open sandbars for roosting. Alterations in the amount of and
timing of flows in the Platte have decreased the once extensive prime
crane roosting sites to a few areas at present. Efforts at restoring
sites in the river are being made particularly by the National Audubon
Society at its Lillian Annette Rowe Sanctuary near Gibbon, NE and The
Platte River Whooping Crane Maintenance Trust, Inc. ("the Trust") at Grand Island,
NE. The Trust, the result of a 7.5 million dollar settlement in the
building of the Grayrocks Dam on the North Platte River in Wyoming, is
designated for acquiring, maintaining and improving habitat for the
endangered whooping crane and other migratory birds. In efforts to restore roosting sites in the
river, bulldozers and other heavy equipment are used to remove trees and
woody vegetation on some islands. Prescribed burns are used when
feasible. This process of removing woody vegetation can be a difficult,
expensive and labor intensive process that does not achieve natural
conditions. Once the vegetation is removed, without the critical flows
in the river to scour the islands, trees and other woody species are
readily re-established. Although debated and controversial, without the
critical flows in the river, the hydrology of the crucial wet meadows
adjacent to the river is altered (Henszey & Wesche, 1993). Because the
successful restoration of crane habitat depends significantly on flows in
the Platte River, restoration groups have become deeply involved in the
politics of water rights and western water law. At present, long-term
re-licensing of Kingsley Dam on the North Platte River in Nebraska is on
hold until a settlement can be made between irrigation and hydroelectric
interests, and scientists, many agencies and environmentalists who want
the timing of the flows in the river to be such as to enhance crane and
other wildlife habitat. In the past two years, a basin-wide Memorandum
of Agreement among the states of Colorado, Wyoming and Nebraska has been
attempted to be worked out regarding instream flows of the Platte and
wildlife habitat. Since settlement of the area in the 1800's, dams and
diversion projects in Colorado and Wyoming have greatly decreased stream
flow, and have altered the timing of those flows into Nebraska. In
addition, projects in Nebraska have further altered the Platte River and
needed wildlife habitat. The parties involved in the Memorandum of
Agreement have been far apart on their expectations and concessions.
WET MEADOW RESTORATION
Historically, cranes fed on tubers of prairie plants and small
invertebrates. As the prairies were converted to agricultural fields,
the cranes had to change food sources. Waste corn in the agricultural fields now
makes up about 90% of the cranes diet. Wet meadows are crucial for
providing snails and other invertebrates. These animals are rich in the
calcium and protein needed to ensure healthy egg production of the
cranes during nesting (Johnsgard, 1991).
Once plentiful, these wet meadows have decreased significantly in number
due to draining for agriculture, and encroaching woody vegetation due to
decreased stream flows and alterations in hydrology. The National
Audubon Society, at its Lillian Annette Rowe Sanctuary near Gibbon, NE
has worked in acquiring and maintaining good crane habitat. Downstream,
at Grand Island, NE the Platte River Whooping Crane MaintenanceTrust Inc. works to
increase the number of, and enhance the quality of, wet meadows for many
avian species. To help meet this goal, four sites in the Big Bend
region of the Platte River were selected by the Trust for restoration and
the progress of these sites is compared to two native wet meadow sites in
the area.
NATIVE WET MEADOW SITES:
The ideal native wet meadow site for cranes is Mormon Island, a 800 ha
wetland complex where 60,000 to 100,000 cranes and other waterfowl have
been observed at one time (Currier, 1995). This site is near Grand
Island, NE. [Note, for exact location of each site discussed, see
Currier, 1995. Note also, that most of the information below is from
Currier (1995) a paper from his presentation at the 1995 Platte River Basin Ecosystem Symposium.] Mormon Island, has been
subject to intensive grazing and some unsuccessful attempts at draining
portions of the area. The Trust acquired this land in 1981 and
implemented a management plan that includes grazing and haying rotations
and prescribed burns. This management plan has resulted in greater plant
production and diversity than existed with the previous management.
The second native site, Binfield, is a 400 ha wet meadow located near
Alda, Nebraska. This somewhat drier site is used for intensive grazing and
haying so there is less species diversity than that found at Mormon
Island. The Trust purchased a conservation easement in 1982 that
specifies no drainage or development of the area. Prescribed burns are
carried out to eliminate woody vegetation.
In the summer of 1989, both the Mormon Island and Binfield sites were
surveyed along transect lines and percent cover of plant species was
estimated. In these native wet meadows, 29 species of grasses, 29
wetland species and 67 forb species were found. Mormon Island had a
wetland species cover of 35%, an amount much greater that the Binfield
site or the restored sites. (See Currier, 1995 for the plant species
lists of each site.)
RESTORATION SITES
Restoration sites range in size from 14 to 130 hectares. One site
was not seeded, while two were seeded with grasses only. The remaining
site was seeded with a wide diversity of grasses and forbs. Attempts at
restoration of hydrology to the four sites ranged from no attempt, to
leveling and reshaping the land to allow for slow drainage. A wind
generated pump was placed at one site. A more complete description of
each restoration site is as follows:
Field - 11 is a 24 ha moderately dry area on Mormon Island that was
cropped for forty years, most recently in alfalfa. In 1988, the site was
enrolled in a Wildlife Habitat Program under state and private auspices.
At that time seeds of big bluestem (Andropogon gerardii), little
bluestem (Andropogon scoparius), indiangrass (Sorghstrum avenaceum) and
switchgrass (Panicum virgatum) were obtained from a commercial source in
eastern NE and drilled into a sorghum stubble. No active seeding of
forbs or wetland species was done; no grazing or haying is carried out on
the site and no alterations in hydrology were attempted. Field-11 is
mowed and experiences an approximately annual prescribed burn.
A 25 ha site near Prosser, Nebraska, Uridil, was tilled for about 20 years,
mainly in corn. This site is adjacent to the south channel of the Platte
River and can experience short term flooding. The Uridil site is
enrolled in the Conservation Reserve Program, and was reseeded with
non-local grass seeds drilled into sorghum stubble in 1990. No forb or
wetland plant species were seeded and no grazing or haying is carried
out. Active management has included a burn in the spring of 1992 and
also placement of a wind-generated water pump in hopes of increasing
surface water ponding at this moderately dry site.
Across the channel from Uridil is Uridil-2, a 14 ha site that was
cropped for the last 20 years, primarily in corn. Previously leveled to
allow gravity irrigation, Uridil-2 is part of a U.S. Fish and Wildlife
Service funded biodiversity study. A portion of the area was scrapped
and reshaped in order to resemble characteristic wet meadow drainage
contours. In 1992, seeds (amount unknown) of more than 100 native
grasses and forbs that had been collected in the Platte River Valley were
spread over sorghum stubble and packed into the soil. Mowing was done in
the fall to control woody species. No grazing, haying, or burning was
done on this moderately wet site that has experienced over-bank flooding.
Located near Elm Creek, NE is the 130 ha Johns site. This area was
formerly part of the river channel but had become riparian forest.
Between 1983 and 1986, trees (40 - 50 years old) were cut and removed. A
Banvel and 2,4-D mix, applied from ground and air; grazing by wild
horses; and burning, were management tools used to limit re-growth of
woody vegetation and noxious weeds. An upstream dike diverts water away from the site for
irrigation. Some sloughs are present, likely created from seepage
beneath the dike. In 1989, dams were built to increase the area of
surface water, but in 1995, they were washed out by high water. This site was not seeded.
The above four restoration sites were sampled for plant species
diversity and percent cover in the same manner as the native sites.
However, Field - 11 was sampled four years after restoration efforts had
begun; Uridil - three years; Uridil- 2 - one year; and the Johns site,
seven years after initiating the restoration. For each site a
dominance-diversity curve (Whittaker, 1975) was calculated.
Not surprising, the highest total number of grass, wetland and forb
species (116) was found at the native Mormon Island site. Uridil - 2, a
restoration site that was heavily seeded, had 105 species while 80 plant
species were observed at Binfield, the other native site. The Field 11,
Johns, and Uridil sites were observed to have approximately 50, 49 and 30
species, respectively.
The dominance-diversity curves, measuring both species richness and
importance, revealed the native sites to be the most diverse and complex
(dominance-diversity values of 42.6 and 39.5). The restored sites
scored much lower using the dominance-diversity curves, with the Uridil
site having the lowest value of 11.4.
The Trust has noted that the percent cover of some plant
species may be the same at restored sites as at reference native sites.
However, the number of grass, wetland, and forb species is significantly
reduced in the restoration sites. (One exception is the Uridil - 2 site
that had been heavily seeded.) In all, the restoration sites have not
reached the diversity of the native wet meadows. Overall, the
restoration sites lacked 63% of the grasses; 78% of wetland species;
and 73 % of forb species that were found in the native wet meadows
(Currier, 1995).
COMMENTARY:
As pointed out by Currier (1995), caution is in order in interpreting the
results, as the restoration sites are only one to seven years old, are
much smaller than the native sites, and seeding or planting did not occur
at all sites. Furthermore, the hydrology of the original wet meadows was
not likely to be found at the restoration sites. Drainage and drawdown
for irrigation and development have occurred and the water table is most
likely further from the soil surface than it was historically (O'Brien
and Currier, 1987). While some efforts were made at pumping at one site,
no mention of exploration of the previously cropped sites for tile lines
and plugging of tiles was mentioned in Currier (1995). According to project managers, tile lines are not commonly used in the Platte Valley. This is in contrast to other parts of the midwest, especially Minnesota and Iowa, where breaking or plugging of tile lines is often necessary for successful wetland restorations.
The goals of these restorations have been to restore, for the greater
than 10 million migratory birds that need this area, a small portion of
the extensive wet meadows that once spread across the Platte River
Valley; to re-establish the diversity of native grass, wetland, and forb
species in these wet meadows; and to re-establish a functioning wet
meadow with the invertebrate and vertebrate species needed by cranes and
other birds. While there is information available on the amount these
wet meadows are used by birds (Savidge and Siebert, 1992), more
documentation is needed. Current efforts are being carried out to sample
the number and diversity of food sources (invertebrates) for cranes in
the wet meadows (Savidge, 1996).
Monitoring of the restoration sites is not as intensive as would be
ideal. Depending on the site, a plant survey was done one to seven years
after the restoration was begun. The use of volunteers to monitor these
restoration sites may be an option given the limited time available to
the staff of the Trust. Colleges in the Big Bend region, native plant
societies or similar organizations are sources of volunteers to survey
plant, bird and invertebrates species.
Overall, seeding of grasses at the restoration sites can be successful,
however the hope that the native species would out-compete introduced
ones has not been realized as of yet. The seeding of forbs, at the
Uridil-2 site, proved to be beneficial in increasing forb species
dramatically. No wetland species were planted at the restoration sites
and recovery of wetland species was poor, except at the Johns site. This
site had been manipulated to increase surface water levels. The
alteration in hydrology, that has occurred in the last 100 years, is
considered the main reason for the lack of re-establishment of wetland
plants in the restoration sites or other wet meadows (Currier, 1995).
Current Political Issues:
Alterations in hydrology of wet meadows and instream flows of the Platte
River are two very politically charged topics. This May, 1996 the
Nebraska Game and Parks Commission ("the Commission") will again consider
the issue of an application for an instream flow right in the Platte
River to enhance wildlife habitat in the river and the adjacent wet
meadows. This application has proved to be controversial as irrigators
and water developers indicated that legal action would occur if the
Commission persisted in its request for a specific instream flow amount
and regime. A "compromise" was worked out with the Commission,
irrigators and other water developers for less instream flow in the river
and for study two wet meadow sites. This "compromise" has been viewed by
many scientists, biologists and environmentalists as inadequate to
maintain flows in the Platte and sustain the hydrology of the wet meadows
for crane habitat. Meanwhile, a Memorandum of Agreement among Colorado,
Wyoming and Nebraska has not been reached, and a lawsuit (Nebraska v.
Wyoming) over instream flows in the Platte River continues in this battle
where there are no clear-cut "good guys" or "bad guys".
I would like to thank Dr. Robert J. Henszey of the Platte River Whooping
Crane Trust, Inc. for his kindness in sending information and speaking
with me regarding wet meadow restoration projects of the Trust.
REFERENCES
Currier, P.J. 1995. Restoration of Functioning Wet Meadows on the
Platte River -- Experimentation with Reseeding, Constructed Wetlands,
and Hydrology. Proceedings of the Platte River Basin Ecosystem System
Symposium. February 28 and March 1, 1995. Kearney, NE.
Farrar, J. 1992. Platte River Instream Flow - Who Needs It?
Nebraskaland. Nebraska Game & Parks Commission. December, 1992.
Hadley, R.F., Karlinger, M.R., Burns, A.W., and Eschner, T.R. 1987.
Water Development and Associated Hydrologic Changes in the Platte River,
Nebraska, U.S.A. Regulated Rivers: Research and Management. Vol. 1.
331-341.
Henszey, R.J. and T.A. Wesche. 1993. Hydrologic Components Influencing
the Condition of Wet Meadows Along the Central Platte River, Nebraska.
Report Prepared for Nebraska Game & Parks Commission by HabiTech, Inc.
Laramie, Wyoming. 84 pp.
Johnsgard, P.A. 1991. Crane Music. Smithsonian Institution Press.
Washington and London. 136 pp.
O'Brien, J.S. & Currier, P.J. 1987. Platte River Channel Morphology and
Riparian Vegetation Changes in the Big Bend Reach and Minimum Streamflow
Criteria for Channel Maintenance. Platte River Trust Report. Grand
Island, NE
Savidge, J., & Seibert, T. 1992. Assessment of Biodiversity and
Indicator Species Groups Along the Platte River. Progress Report
Submitted to the U.S. Fish & Wildlife Service, Grand Island, NE
Savidge, J. 1996. Testimony given at NE Game and Parks Commission
Hearing on an Application for an Instream Flow Right in the Platte River
for Wildlife Habitat. March 22, 1996. Lincoln, NE
Whittaker, R.H. 1975. Communities and Ecosystems. MacMillan Publishing
Co., New York. 375 pp.
Williams, G.P., 1978. The Case of the Shrinking Channels - The North
Platte and Platte Rivers in Nebraska. U.S. Geological Survey Circular
781, 48 pp.
Return to the
Restoration & Reclamation Review Home Page