|
2008 Federal Duck Stamp Contest
Waterfowl Identification Guide Comprehensive Conservation Plan Phone: 218-8474431 |
Prairie wetlands and prairie streams are an important part of the prairie ecosystem. Minnesota is naturally rich in wetland and riverine habitats. Western Minnesota is part of the prairie pothole region, characterized by numerous, shallow wetlands known as potholes. These wetlands provide essential fish and wildlife habitat, permit ground water recharge, and act as filters of sediment and pollutants. They reduce floods by storing water and delaying runoff. The region once included about 20 million acres of these small wetlands. They were unconnected and poorly drained and in the spring they retained water, acting like a great landscape sponge. Over the course of the season, water drained slowly.
Settlers found the shallow wetlands difficult to farm. In addition, the wetlands kept the water table high so much of the land was saturated in a wet year. When the land was converted to farms, the new owners built drainage ditches, straightened streams and drained shallow wetlands off their land. Today, only about 5.3 million acres remain in 2.7 million basins within five states. Now, in the spring, water rushes off the land and floods the streams and rivers. Drainage has been so extensive that in many areas the water table has been lowered and the hydrology of the entire region has been transformed.
More than 78 percent of the remaining wetland basins are smaller than 1 acre in size. Nearly two out of three of the remaining wetlands in Minnesota are privately owned; consequently, they are vulnerable to continued drainage, development, and pollution.
The Wetland Management Districts have focused on saving and restoring the small wetlands of Western Minnesota. They have been remarkably successful in saving a variety of wetland types. Wetland diversity is important because wetlands change continuously; a single wetland cannot be maximally productive all the time. Waterfowl use specific types of wetlands at different times during the breeding season. Laying hens may forage in ephemeral, temporary, and seasonal wetlands early in the season and shift to semipermanent and permanent wetlands after the brood is hatched. Marsh birds need a variety of wetlands in close proximity so they can shift from one wetland to another as the wetlands cycle through different phases. It is very important that natural wetland complexes be preserved. Wetland complexes include a variety of basins, some shallow and some deep, in close proximity. Diverse wetland complexes are rare today because most shallow ephemeral, temporary, and seasonal basins have been drained.
Saving single, isolated wetlands is much less valuable than saving several wetlands in a wetland complex. The Wetland Management Districts focus on acquiring wetland complexes with a variety of wetland types.
The fluctuating water levels in the shallow wetlands are natural to the dynamic pattern of precipitation in the prairie. The changing water level results in circular bands of vegetation around each basin because different plant species have different tolerances for saturated soils. The depth of the basin also affects the kind of vegetation that grows. The drying pattern is one of the features used to classify wetland basins (Cowardin et al.). Deeper basins have perennial emergent vegetation such as cattail and dry every 5 to 10 years. Wetlands that dry every other year or on a several year cycle are called semi-permanent or permanent wetlands. Basins that dry every year are temporary and seasonal wetlands. Some very shallow basins dry early in the spring after the frost leaves the ground and as a result are called ephemeral wetlands.
Freshwater wetlands like those in the prairie pothole region are among the most productive in the world (Weller 1982). The dynamic water cycle creates a rich environment for many waterfowl and other marsh birds. Cycling water accelerates decomposition of marsh vegetation, resulting in a natural fertilizer. When the basins recharge in the spring, the water becomes a soup of nutrients and supports a diverse and healthy population of aquatic invertebrates, which feed reproducing waterfowl and marsh birds throughout the spring and summer. In the larger basins, the vegetation changes from densely closed cattail or bullrush cover to completely open over a period of years (Figure 1). In the process of transition, the cover vegetation moves through a phase, known as hemi-marsh, when clumps of emergent vegetation are interspersed with open water (Weller 1982). In this phase, the structure of the vegetation itself creates habitat and stimulates the production of aquatic invertebrates. The marsh, in this phase, hosts the maximum number of marsh birds. Unfortunately, the phase is only temporary and most wetlands cycle out of it in 1 to 3 years.
Figure 1: Marsh Vegetation Cycles
The prairie potholes are too shallow to be fish habitat but they have been used in the past as hatcheries for minnows and walleye fingerlings. Leeches are also harvested from these shallow ponds. Unfortunately, many of these artificially introduced native species consume the same aquatic invertebrates as waterfowl. Fathead minnows occur naturally in some wetlands in the region and have a significant negative effect on the invertebrate populations of the wetlands (Hanson and Zimmer 1999).
Wetland restoration and management are high priorities in the Districts. In many areas, the entire hydrology of the area has been altered and restoration is not always a straightforward matter of plugging drains and filling in ditches (Galatowitsch and van der Valk 1994). Restored wetlands employ water control structures for water level management to mitigate the disruptive impact of wide scale drainage that has altered natural water cycles. Many wetlands on WPAs are flooded because surrounding wetlands on private land have been drained and the excess water moves into the WPA. Water control structures are often necessary, but these structures require funding to install and staff to maintain. Neither are in adequate supply to do what is needed.
Partners for Fish and Wildlife Program
Wetland Districts in Minnesota have led the nation in the sheer number of wetlands restored through the cooperation of private landowners in the Partners for Fish and Wildlife Program (Private Lands). The program assists private landowners with the improvement or restoration of wildlife habitat on their land. Technical assistance, contracting, cost-sharing assistance, and actual earth work is provided to private landowners throughout the Districts. Since the program's inception in 1987, 12,000 wetlands totaling more than 40,000 acres have been restored. However, some Districts are now finding it more difficult to find landowners willing to restore wetlands. More staff effort is required with longer trips and greater expense to seek out landowners willing to restore wetlands. Managers have also begun to explore assisting landowners with efforts to restore native prairie and riparian areas.
Districts have also restored more than 10,000 acres of native grasslands on private property through the Partners for Fish and Wildlife Program during the same period. In the past 2 years, new funding sources within the Partners for Fish and Wildlife Program have placed added emphasis on riparian and instream habitat restoration, and this has the potential to create additional opportunities for the Districts to accomplish habitat restoration on private lands.
U.S. Department of Agriculture (USDA) programs have created many new opportunities for Districts to assist in the restoration of a variety of trust resource habitats on private lands. The USDA's Conservation Reserve Program (CRP) has placed an emphasis on wetland and native prairie restoration as a condition of enrollment, and many new participants are making their lands available for wildlife habitat restoration. This presents an important role for the Districts to lend their restoration experience and expertise to make these CRP restorations as high-quality as possible. The USDA's Wetlands Reserve Program (WRP) likewise presents opportunities for Districts to accomplish migratory bird objectives on private lands utilizing other agency programs and dollars by making experience and expertise available to implement habitat restoration projects.
The Districts' perpetual easement program, which encompasses both wetland and conservation easements (both wetlands and uplands on a property), has greatly benefited from the success of the Partners for Fish and Wildlife Program over the past 10 years. Many of the private landowners who have restored wetlands on their lands through the Partners Program have since come back to the District seeking establishment of a permanent easement on their property to offer protection to their project in future years. In some Districts it is fair to say that the vast majority of new easements recorded in the past few years first started as Partners projects. This continues to meet the needs of landowners who wish to improve their land for wildlife, for themselves and for future generations.
By providing habitat restoration funds to complete restoration projects initiated by the Districts as well as technical assistance funds to provide restoration experience and expertise to other agencies' programs, the Partners for Fish and Wildlife Program puts the Wetland Management Districts in a wonderful position to accomplish a multitude of, and a variety of, trust species habitat restoration projects over the next 10 years.
Prairie Restoration
Prairie landscapes are much more diverse than they seem at first glance. They contain hundreds of species of plants, invertebrates, and wildlife. Some prairies contain as many as 200 plant species. The landscape is dominated by a relatively small number of widespread, sod-forming bunch grasses such as big bluestem, northern dropseed, and porcupine needlegrass, but flowering plants constitute the greatest number of species (80 percent in some areas). Most abundant members are from the pea and sunflower families such as wild indigos, prairie clovers and scurf peas (pea family); and asters, gay-feathers, goldenrods, coneflowers, and sunflowers (aster family) (Henderson and Lambrecht, 1997).
Over the past decade, virtually all plantings of upland cover on Waterfowl Production Areas have been with native grasses. In recent years, a more diverse mixture of native forbs and warm and cool season native grasses have been used. Plants within a single species vary with latitude (called ecotypes) and an effort is being made to plant local ecotypes in restorations. Harvesting techniques of existing tallgrass prairie and refinement of the cleaning and seeding process has made seed gathering easier. However, many native prairie forbs remain in short supply and are extremely costly for large areas.
Prescribed fire remains a critical tool for maintaining the diversity and vigor of existing and restored prairie plants. Prescribed burns can only be done during a small window of time in the spring, so the number of acres that can be burned each spring is limited. As a result, most WPAs can not be burned on a rotation frequent enough to suppress invading shrubs and trees. Some of the Districts use haying and grazing as additional means of maintaining grassland integrity.
The Districts also manage grasslands through the selective application of herbicides during restoration. In 1990, 15,825 pounds of active ingredients representing 20 herbicides were applied to 15,533 acres of Service-managed lands in Minnesota (USFWS 1990). The most heavily and most frequently used chemical was 2,4-D. In 1987, approximately $100,000 was spent on noxious weed control on approximately 16,000 acres of District lands (USFWS 1992). Because of concern that chemical use could impact water quality (See Issue 9), the Twin Cites Ecological Services Field Office conducted a 2-year study beginning in 1992 to determine the impact of the herbicide application on wetlands in the Districts. The results indicated that concentrations of 2,4-D were consistently low and at concentrations that have not been shown to have an adverse affect on aquatic life (Ensor and Smith 1994).
Rare Communities
Waterfowl Production Areas provide one of the last bastions of grassland and wetland habitat in the prairie area of Minnesota. These areas provide some of the last remaining habitat for threatened, endangered, rare or unique wildlife and plants. Examples include the threatened western prairie fringed orchid and prairie bush clover, and numerous species of grassland and wetland-dependent species that are declining in numbers. There is a need to have better baseline information on what species are present on each WPA, and to monitor the effects of wetland and prairie restoration efforts on these species of special concern.
Minnesota County Biological Survey (Survey) conducted systematic surveys of rare biological features from 1987-1995. The goal of the Survey was to identify significant natural areas and to collect and interpret data on the distribution and ecology of rare plants, rare animals, and natural communities. The Nature Conservancy, through a cooperative agreement with the Service, consolidated these data and the data of the Natural Heritage Information Systems of the Minnesota Natural Heritage, and Nongame Research Program. From this data, the existing protected areas within Minnesota were mapped and community types were identified. Within the northern tallgrass prairie ecoregion (Iowa, Manitoba, Minnesota, North Dakota, and South Dakota), 97 terrestrial natural communities have been documented.
Rare communities most at risk are the mesic, wet, and dry prairie types. Three grassland communities (mesic tallgrass prairie, sedge meadow, and lake plain wet prairie) are critically endangered in the United States (Noss et al., 1995). The tallgrass prairie ecosystem includes the following community types:
-
Dry Prairie Mixed Emergent Marsh
-
Mesic Prairie Shrub Swamp
-
Wet Prairie Aspen Woodland
-
Mesic Brush Prairie Aspen Openings
-
Wet Brush Prairie Dry Oak Savanna
-
Calcareous Seepage Fen Mesic Oak Savanna
-
Rich Fen Oak Woodland/Brushland
Some community types are broken down into subtypes, for example: Sand-Gravel Subtype of the Dry Prairie Type. Others include hill and barrens (dry prairie type), saline (wet prairie type), and prairie (calcareous seepage fen type). The prairie type of Calcareous Seepage Fen is one of the most valued of the rare plant communities in the Districts. These fens typically are surrounded by wet-mesic prairie species. The seepage area itself commonly contains patches of emergent aquatic species such as cattail, hard-stemmed bulrush, and common reed. Such areas occur throughout the Districts but are more common in the Lake Agassiz Beach Ridges.
Prairie community types are diverse, some are rarer than others; but with less than 1 percent of all northern tallgrass prairie remaining, special consideration is warranted for all types and subtypes. It can be argued that all intact prairie plant communities are rare. Tallgrass prairies have the highest percentage (65 percent) of rare community types of any group. The importance and uniqueness of individual tracts become apparent when ecotype variation is considered. For instance, warm season grasses generally vary one day in flowering time with each 9-14 miles in a north-south gradient. No doubt many more subtle ecotype variations occur.
Due to the disproportionate loss of community types, individual plant species of the prairie are becoming rare. For example, the western prairie fringed orchid was historically widespread and common in calcareous mesic to wet mesic prairies and sedge meadows. Wholesale conversion of its habitat to agriculture has resulted in the plant being placed on the Federal endangered species list.
Plant Species of Concern
"Species of concern" is an informal term in this document for species which the Service has incomplete and inconclusive information, but which might be declining in range, numbers, or security. Service biologists confer with state agency botanists and other experts, and use state natural heritage program data bases and other published and unpublished information to follow the welfare of these species. Species of concern have no standing or protection of any kind under the Endangered Species Act (Act) and they are not candidates for listing under the Act. Nevertheless, the Service is interested in them and is alert for need to provide early assistance to these species to avoid the need to list them under the Act.
These species are a diverse group of plants united by two factors: (1) the Service is watching them, and (2) they occur within the general area and thus could appear in or near District tracts. It is impossible to predict which, if any, of the species may occur on tracts managed by the Districts. It is also impossible to predict how the occurrence of one of these species on or near a tract would factor in decisions regarding individual tracts beyond the Service's intent to recognize these species as valid and necessary components of a healthy, functioning tallgrass prairie ecosystem and as indicators of prairie tract quality.
The Minnesota Department of Natural Resources maintains an official state list of plants being watched for changes in abundance and distribution, and of plants that are endangered or threatened and protected by state law. There are approximately 80 such species in the counties of Minnesota. Biologists of the state natural resource agency and the Service maintain ongoing communication regarding these species, some of which are excellent indicators of prairie quality.
Listed Plants
This section describes plants that are federally listed under the Endangered Species Act of 1973, as amended, and are listed as either endangered or threatened.
Prairie bush clover, Lespedeza leptostachya: Occurs in dry, gravelly hill prairies and in thin soil prairies over granite bedrock. Common on prairies with big bluestem (Andropogon gerardi) and Indian grass (Sorghastrum nutans). More sites are known for this species than were known when it was listed and it appears able to grow in disturbed areas. The species may be stable or, if declining, declining slowly. The need for protection remains.
Western prairie fringed orchid, Platanthera praeclara: Occurs in moist, calcareous subsaline prairies and prairie sedge meadows and swales (Coffin and Pfannmuller 1988). The species may be stable, but loss of tallgrass prairie habitat has markedly reduced its original range. Present sites are threatened by human activities and land use changes and by invasion by leafy spurge (Euphorbia esula).
External Threats
Drainage and Pesticides
Waterfowl Production Areas are often islands in a sea of intensive agriculture. Natural drainage patterns have been altered throughout the landscape, increasing the frequency, intensity, and duration of water flowing into many units. Siltation, nutrient loading, and contamination from point and non-point sources of pollution are a serious problem on many WPAs. Waterfowl Production Areas are also threatened by farming trespass, dumping, wildfires, and pesticide applications on adjacent agricultural land. A recent study in Ontario examined the effects of habitat and agricultural practices on birds breeding on farmland and determined that the most important variable decreasing total bird species abundance was pesticide use (Freemark and Csizy 1993).
Recent changes in agriculture have accelerated the impact of pesticides on surrounding land. Genetically altered Round-up ready corn, soybeans, cotton, and sugar beats have expanded the window of opportunity for pesticide applications and promises to kill everything green on fields except the genetically altered crops. Another altered crop, Bt. Corn, contains a genetically engineered insecticide. Even the pollen from this plant can kill certain insects, such as monarch butterflies.
Research has shown that insecticides commonly used for sunflowers, soybeans and corn can kill wildlife directly and indirectly (e.g. by decreasing the amount of food available to ducks). For example, ducks feed on grain much of the year but in the spring they shift to aquatic invertebrates (insect larvae, amphipods, snails, etc. and depend on this food source for reproduction and survival. Even when aerial pesticide applications are done carefully and wetlands are avoided, the chemicals drift into wetlands in measurable amounts and kill aquatic invertebrates (Tome et al. 1991 and Grue et al. 1986).
Insecticides have a direct effect by killing aquatic invertebrates, but herbicides also have an indirect effect on food available to waterfowl. The Service conducted a study of the impact of agricultural chemicals on selected wetlands in four of the Wetland Management Districts (Ensor and Smith, 1994). Herbicides from surrounding agricultural land enter wetlands and disrupt the functional interaction between vegetation structure and aquatic invertebrate life. The changing dynamic reduces food available to breeding waterfowl.
Seasonal and semipermanent wetlands (the majority of WPA wetlands) are the most exposed to agricultural chemicals. These wetlands are small and interspersed with croplands, which increases the probability of pesticides from overspray and aerial drift. Most herbicides and insecticides are applied to crops in the spring and early summer, coincident with maximum runoff and waterfowl breeding. Ensor and Smith (1994) write: "A result of our survey... indicates that prairie pothole wetlands may involve interactions of multiple herbicides (and potentially insecticides) comprising chemical 'soups' unique to individual wetlands."
This study showed that "typical agricultural use" of pesticides on surrounding land had a significant impact in reducing the biological quality of WPA wetlands. Currently, the Minnesota Pollution Control Agency (MPCA) exempts "normal farming practices" from the State's wetland protection.
Invasive Species
Noxious weeds are a continuing problem both ecologically and socially/politically. Invasive species present a daunting challenge to land managers. Canada thistle, leafy spurge and spotted knapweed can displace native vegetation over large areas and are a serious concern to neighboring farmers and county officials. Purple loosestrife can effectively displace cattails and other native wetland vegetation and turn productive marshes into a sea of purple flowers. Carp can destroy native submergent vegetation, which provides the base for invertebrates. Minnows, often from past stockings by bait dealers, can cause serious damage to wetland food chains by reducing invertebrate populations needed by breeding waterfowl and ducklings.
Control of these problem species is often costly, both in terms of chemicals, equipment, and staff time. Managers strive to use a balanced approach in controlling these species. Direct control, such as chemical application or mowing, is often needed on serious problem areas. Once healthy native plant communities are reestablished, they can often compete successfully against invasive weeds. Water level control, including complete drawdowns, can eliminate carp and minnow populations on wetlands where this capability is present. Virtually all Districts are experimenting with biological controls by introducing insects that control the invading plant in its native country.
Rural Development
Rural development also threatens District lands in counties with growing populations, such as Wright County. Lands adjoining WPAs are often seen as highly desirable rural building lots that are purchased as small hobby farms or rural homesites. This can result in the WPA being "ringed" by homes, with a series of negative impacts on the WPA. Such development can limit future management such as prescribed fire; increase trespass on District lands by neighbors using ATVs, horses, or vehicles; increases threats to wildlife from stray pets (cats and dogs); increases use of District land by neighbors for illegal uses such as dumping, gardening, equipment storage, etc.; and can place hunters and neighbors at odds over concerns about safety during the hunting seasons. Large-scale rural development would also bring threats from noise and storm water runoff.
Note: The above information is an excerpt taken from the Detroit Lakes WMD Comprehensive Conservation Plan (CCP). The above cited references and other useful information can be found by reviewing the full plan at the following link: Detroit Lakes CCP.
