Ecosystems Historically in the Watershed

--Lake Michigan Basin Inland Wetlands

Inland Wetland System

The inland wetland system–wetlands away from the Lake Michigan shoreline–is the reservoir for water in the Lake Michigan drainage basin. There are many types of inland wetlands, including fens, bogs, wet meadows, and wet forests. The health of inland wetlands is dependent on the quantity and quality of groundwater and surface water. Inland wetlands help to regulate the basin's volume of water as well as sediments and chemicals. They also store nutrients and serve as the nutrient exchange vehicle for the diversity of species that use inland wetlands as habitat and feeding areas. Both wetland and upland species breed and feed in Lake Michigan's inland wetlands (The Nature Conservancy 1994).

Inland Wetland System: Description

Wetlands are defined in numerous state statutes. For example, Wisconsin statute [Section 23.32 (1)]defines wetlands as areas "where water is at, near, or above the land surface long enough to be capable of supporting aquatic or hydrophytic vegetation and which has soils indicative of wet conditions." Federal wetland definitions are provided by the U.S. Army Corps of Engineers and the National Wetland Inventory.

The inland wetland system is composed of a variety of wetland types. Each wetland type has a different suite of animal and plant species and habitat conditions. For example, the Pine and Popple River area in northeastern Wisconsin is a wet northern forest. It occurs on acid peat and is dominated by black spruce, tamarack, white cedar, and balsam fir, as well as an understory of mosses, sedges, and shrubs.

The Turner Creek Wetlands in the southwestern part of Michigan's lower peninsula, on the other hand, has a wet prairie complex, a grassland of bluejoint grass, sloughgrass, and big bluestem on wet soils (The Nature Conservancy 1994).

The inland wetland system is an important part of the water cycle for all ecosystems in the Lake Michigan basin. They are generally a buffer between lakes and ponds and upland areas. They trap sediments, remove nutrients and soak up floodwaters, thereby functioning to keep water clean. They are discharge and recharge areas for groundwater. They provide diverse habitats for many plants and animals (Wisconsin Department of Natural Resources 1995).

The role of inland habitats in maintaining water quality is perhaps overshadowed by their importance in regulating water flows and levels. From a basin-wide perspective, the inland habitats are the principal collectors of precipitation for the basin. The ability of forests and wetlands to store and release water is critical to moderating tributary and groundwater flows to the lakes (The Nature Conservancy, 1994).

Inland habitats moderate tributary flows, reduce erosion and sedimentation associated with flooding, and thus moderate the seasonal and long-term fluctuations of lake levels. Many animal species move between different habitats, with periods ranging from daily through seasonally to once or twice in their life cycle. In this way, habitats other than the one they are normally associated with, can play a critical role in the survival of the species, especially when normally dispersed populations concentrate in very small areas. In such a case, this habitat becomes far more important than what is suggested by the community of species that are more permanent residents. Examples of several different kinds of periodic use are summarized below.

Migration Stopovers

Historically, the marshes of Wisconsin's Winnebago Pool Lakes, as well as other areas in the Great Lakes such as the Detroit River, Lake St. Clair, Long Point and Western Lake Erie, have been important resting and feeding stops for the eastern population of canvasback duck, which winters on the Atlantic Coast. This population declined from 400,000 birds in the early 1950s to less than 147,000 by 1960 and has just finally recovered to its former levels.

The canvasback duck has rigid habitat requirements and behavioral traits that limit its adjustment to environmental change. It does not tolerate disturbance by boat traffic and depends strongly on wild celery. Densities of wild celery tubers decreased by 72 percent from eutrophication, sedimentation, carp, and pollution at two of five locations where ducks once fed between 1950 and 1985 (Schloesser and Manny 1990; Kahl 1991). Several authors have suggested that the decline in canvasback numbers is at least partially linked to the reduction in forage on their migration routes (Bellrose and Crompton 1970; Mills and others 1966; Trauger and Serie 1974).

Spawning and Nursery

Many of the fishes of the open lake and tributaries move to the shallow waters or wetlands to spawn. In this respect, their needs are very specific: a certain kind of substrate, a certain amount of current, depth and temperature and within a narrow time-window. Often they return to the same places where they hatched. In a manner similar to waterfowl, during spawning a widely-dispersed population becomes concentrated in a habitat of relatively small size. For these populations, these spawning habitats become far more important than their relative size would suggest. An atlas of spawning grounds in Lake Michigan is available at http://www.glsc.nbs.gov/information/atlas/index.htm.

Overall, inland wetlands are exceptionally rich in plant and animal species. Many of these species are threatened or endangered. Plants include, among many, calypso orchid, tussock bullrush, umbrella sedge, and algal-leaved pondweed. Animals include reptiles and amphibians such as the Blanding's turtle, wood turtle, and Massausauga rattlesnake, and Blanchard's cricket frog; birds such as the trumpeter swan, yellow-throated warbler, and red-shouldered hawk; and Lepidopterans such as the silphium borer moth. It is estimated that 32 percent of the State of Wisconsin's threatened and endangered plants and animals are wetland-dependent (Wisconsin Department of Natural Resources 1995).

Inland Wetland System: Assessment

Millions of acres of inland wetlands have been lost in the Lake Michigan basin to agriculture, industry and urban development over the last century. Over the last two centuries, wetland losses in the four states at least partially within the Lake Michigan basin have been disproportionately greater than in many other U.S. regions. Since the 1780s, Lake Michigan basin states have lost an estimated 21.9 million (62.9 percent) acres of wetlands out of their 34.8 million original wetland acres. Wisconsin has lost about 47 percent of its original ten million acres of wetlands (Wisconsin Department of Natural Resources 1995). Illinois has lost approximately 85 percent of its wetland acreage, Michigan has lost greater than 50 percent of its wetland acreage, and Indiana has lost greater than 70 percent of its acreage (U.S. Fish and Wildlife Service No Date). These figures compare with an average loss of 52.8 percent nationwide. There are an estimated 12.9 million acres of wetland remaining in the four states, representing more than 12.3 percent of the wetlands within the lower 48 states (Dahl 1990). Recent historic losses of wetlands in the Great Lakes basin have been estimated to be 20,000 acres/year (Great Lakes Basin Commission 1981).

State and federal regulatory programs have begun to stem the tide of losses; however, exemptions for agriculture, forestry, and other uses do not protect all wetlands from being destroyed. Fortunately, acquisition of major inland wetlands for waterfowl and fishery management was initiated by groups such as Ducks Unlimited and resulted in wetland protection. Management for waterfowl and fish have helped other wetland-dependent species, such as wading birds and sandhill cranes. Restoration of many wetlands is also taking place, although restorations have not proved to be as rich or diverse as the original wetlands.

Text excerpted from the Lake Michigan Lakewide Management Plan, U.S. Environmental Protection Agency Great Lakes National Program Office, 2000.

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