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Wetlands are characterized by the presence of water that saturates the soil or covers the land for most or all of the year. This leads to the development of plant and animal communities that are adapted to these conditions and which differ from those in purely aquatic (lakes, rivers) or dry land environments.
Twelve thousand years ago the last great ice age was coming to an end in Michigan. As the glaciers melted, they left behind a changed landscape. Water was everywhere. New river channels cut through the sands and gravels and drained into broad lowlands, flowing finally into lake basins carved by the glaciers. Massive chunks of ice became kettle lakes, while winds sculpted coastal dunes of shifting sand.
Slowly drainage patterns stabilized, and lake levels fell. Forests returned on the higher ground, while vast grassy marshes spread across the former lakebeds and coastal lowlands. Over time, the shallower kettle lakes filled with plant debris, becoming bogs. Perhaps a third or more of the state was covered by wetland habitats. These new habitats filled with wildlife in great abundance, including mastodons, caribou, and bear sized giant beavers. These species soon disappeared, to be replaced by more familiar creatures.
A succession of American Indian cultures in Michigan made efficient use of wetlands. Open waters of lakes and rivers served as transportation corridors, while swamps and marshes produced wild game and food plants. These native Americans understood the value of wet places. Then, about 200 years ago, an invasion of Europeans arrived, bringing with them the view that the wilderness was an enemy, to be subdued and conquered. Wetlands, in particular, were considered mysterious and forbidding places-wastelands to be drained or filled at the earliest opportunity. The prevailing attitude, reinforced by acts of Congress and State government, led to the destruction of millions of acres of wetlands.
This "reclaim the wetlands" attitude continued to the middle of this century, when nearly three-quarters of the original wetland area in our state (estimated at over 11 million acres) had been destroyed. Michigan's abundant freshwater resources, a gift of our glacial past, have too often been squandered and wasted. Only in recent years have we begun to realize the essential role that wetlands play in nature, and the human economy.
But despite new laws and the efforts of government and private conservation groups, the destruction of wetlands continues, though on a reduced scale.
Wetlands are a blending of lands and water in varying quantities, and many different types have been identified by biologists. The three major types are marsh, swamp, and bog. These can be defined more specifically:
MARSHES have standing water from less than an inch to several feet deep. The amount of water can fluctuate seasonally or from year to year. Marshes might generally be called "flooded grasslands." They are dominated by soft stemmed emergent plants such as cattails, grasses, sedges, rushes, arrowhead, pickerel weed, and smartweed. In deeper water are found lily pads and submerged plants such as elodea, milfoil, and pondweed. Marshes are critical for many fish species that live and/or breed there. Marshes offer primary breeding and feeding habitat for water birds (ducks, geese, herons, cranes, rails) and song birds like the marsh wren and yellow warbler, as well as numerous frog species, reptiles (turtles, water snakes), and mammals such as muskrats, beaver, and otter. In Michigan, marshes are found at the edge of some rivers and lakes, in lowlands and depressions, and in swales between sand dunes.
SWAMPS can best be described as flooded woodlands or shrublands. Unlike marshes, they are dominated by woody plants. The soil is usually waterlogged throughout the growing season, though some swamp soils may become dry during the hot summer months. In Michigan, trees and shrubs found in swamps include red and silver maple, cedar, balsam, willow, alder, black ash, elm, and dogwood. Swamps occur most often along streams or on floodplains, in flat uplands, or shallow lake basins. Numerous wildflower species are found in swamp habitats, including the cardinal flower and yellow ladyslipper. Characteristic of the many swamp living animals are wood frogs, gray treefrogs, salamanders, barred owls, waterthrushes, prothonotary warblers, water shrews, and raccoons.
BOGS occur where accumulations of decaying vegetation form mats that eventually cover and then fill in old ponds or kettle lakes. In some bogs, open water may be surrounded by floating vegetation, while other bogs are totally grown over and consist of spongy, waterlogged peaty soil covered by sphagnum moss. Bog soils are usually highly acidic, and oxygen and nutrient deficient. Acid tolerant plants found in or around bogs include woody plants such as labrador tea, poison sumac, tamarack, and black spruce. Many species of orchids prefer bog habitats, as do insect eating sundews and pitcher plants. Bogs shelter many rare animal species, including the spotted turtle and southern bog lemming.
The bogs most people are familiar with are these acidic bogs. There is, however, a distinctly different type of bog called a fen. Its higher alkalinity and productivity is the result of water passing through calcareous deposits. Fens typically have high plant diversity due to higher nutrient levels; many plants are prairie plants such as prairie white fringed orchid, sweet grass, the bluestems, and blazing star. Unusual animals of fens include the eastern massasauga rattlesnake and rare butterflies such as Mitchell's satyr and the Powesheik skipper.
Vernal Ponds are small bodies of standing water that form in the spring from meltwater and are often dry by mid summer. While not usually considered in official definitions of wetlands, vernal ponds are very important in the life cycles of many wildlife species. In particular, many species of amphibians (frogs and salamanders) depend on these temporary ponds for breeding sites. This allows the vulnerable aquatic larvae (e.g. tadpoles) to mature in a place free of fish predators.
Descriptions and photos of wetland types used by the Michigan Frog & Toad Survey.
The linked table lists some places where the different types of wetlands can be found in Michigan. Remember that wetland habitats are fragile and easily damaged by human activity. It is best to visit them in small groups, and to avoid wading through areas of soft muck soils and shallows where sensitive plants may occur. Many of the areas listed in the table have boardwalks traversing the wetlands or observation towers to improve access, and to reduce human impact.
Because they occur where the dry land meets the water, wetlands play a critical role in the management of our water based resources.
Acre for acre, wetlands produce more wildlife and plants than any other Michigan habitat type. Wetland species also comprise a critically important segment of these species. For example, Michigan boasts about 2300 native plant species; 50 percent of these are wetland species and over 25 percent of the wetland species are threatened or endangered. More than 40 percent of the 575 vertebrate (with a backbone) wildlife species in Michigan live in or utilize wetlands. This includes 10 to 15 of the 66 mammals, 180 of the 370 birds, 22 of the 28 reptiles, and all of the 23 amphibians.
Here are a few other things that wetlands do:
The extent of wetland habitat was once controlled by natural processes. Marshes along the Great Lakes and drowned river mouth lakes vary in size, depending on rainfall trends and Great Lakes water levels. The natural filling of old glacial lakes with plant remains and sediment will create bog habitat. Eventually through continued succession, open water may be eliminated, replaced with a continuous sphagnum bog or a wet meadow. Floodplain swamps may shrink or increase with the normal changes in a river's channel over time. Over the long term, such natural change is inevitable. Wetland areas in Michigan have been growing, shrinking and re forming according to natural cycles since the last Ice Age and before, and these cycles continue today.
The last century has seen a greatly increased rate of wetland loss due to filling and drainage by man. Prior to World War 11, drainage to expand agricultural lands accounted for most of this loss. Recently, much wetland destruction has been caused by commercial, industrial, and residential expansion. The estimated 11 million acres of Michigan wetlands existing in pre settlement times has now been reduced to less than 3 million acres. Recent legislation has slowed the loss rate somewhat but threats to these habitats, particularly the smaller wetlands, continue in many areas.
State and Federal legislation that regulates wetland use and alteration:
Both of the following federal laws are administered by the U.S. Army Corps of Engineers. In Michigan, the Section 404 federal authority associated with interior (inland) waters and wetlands was assumed in 1984 by the Goemaere Anderson Wetland Protection Act. Joint jurisdiction between MDNR and the U.S. Army Corps of Engineers still exists in commercially navigable waters and wetlands contiguous to those waters.
Further Michigan legislation that regulates wetland use and alteration:
Other laws both at the local level and state level affect wetland areas. Contact DEQ before initiating any project involving wetland alteration, or if you have a question concerning a wetland development project in your community.
Freshwater Marshes, Ecology, and Wildlife Management, Milton W. Weller, University of Minnesota Press, Minneapolis, 1987.
Wetlands , The Audubon Society Nature Guides, William A. Niering, Alfred A. Knopf Publishing, New York, January 1987.
Michigan Wetlands Yours To Protect. A Citizen's Guide to Local Involvement in Wetland Protection, Tip of the Mitt Watershed Council, Box 300, Conway, Michigan 49722.
Wetland Protection Guidebook, Michigan Department of Environmental Quality, Lansing, Michigan 48909,1988.
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