Until recent years, wetlands have been regarded as wastelands - sources of mosquitoes, flies and unpleasant odors. Most people felt that they were places to be avoided, or eliminated. It was accepted practice to drain or fill wetlands for other uses, or use them as dumping grounds. As a result, more than half of America''s original wetlands have vanished.The term wetlands includes marshes, swamps, and bogs and are transitional areas between land and water bodies. They may be covered in shallow water most of the year, or be wet only seasonally. Plants and animals found in wetlands are uniquely adapted to these wet conditions. Wetlands can be found in virtually every county of every state in the nation, from arctic tundra wetlands in Alaska, to peat bogs in the Appalachians, to riparian wetlands in the arid West.
Wetlands play important roles in maintaining the health of our ecosystems.
- They provide critical habitats for fish and wildlife, purify polluted waters, and check the destructive power of floods and storms.
- Upland wildlife such as deer, elk, and bear commonly use wetlands for food and shelter.
- Wetlands are particularly vital to many migratory bird species. For example, wood ducks, mallards, and sandhill cranes winter in flooded bottomland forests and marshes in the southern U.S., and prairie potholes serve as breeding grounds for over 50% of North American waterfowl.
- About 35% of all plants and animals listed as endangered species in the United States depend on wetlands for survival.
- Wetlands also provide recreational opportunities such as fishing, hunting, photography, and wildlife observation.
The quality of the environment is directly dependent upon the healthy function of wetlands. Wetlands act as natural water purifiers, filtering sediment and absorbing pollutants in surface waters. In some wetland systems, this cleansing function enhances the quality of groundwater supplies as well. Wetland vegetation binds the soil and slows the downstream movement of sediment by absorbing the energy of storm waves, slowing water currents and store excess water during rainstorms. This reduces downstream flood damage and lessens the risk of flash floods. During periods of drought, stored wetland waters supply rivers and streams helps keep them from drying up.
Where do wetlands exist, and what are the different types?
A wide variety of wetlands have formed across the country due to regional and local differences in climate, geology, topography, hydrology, soils, vegetation, water chemistry, and other factors. Although there are many different wetland types, the two largest divisions is by Non-Tidal and Tidal Wetland types.
Non-Tidal Wetlands, found in-land, account for most of the wetlands of the United States. Peatlands are inland wetlands containing thick deposits of slowly decaying plant material called peat. "Bogs" and "fens," the major types of peatlands, occur in old lake basins or lower land areas in the Great Lakes states, portions of the Northeast, the Appalachian Mountains, much of Alaska, and along the Southeastern Coastal Plain. Unusual plants such as sphagnum moss, pitcher plants, sundews, Venus'' flytraps, and a number of orchid species are uniquely adapted to the nutrient-poor acidic conditions found in bogs. Fens are richer in nutrients and less acidic than bogs, and are more typically covered by sedges, willows, grasses, and reeds.
- Southern Deepwater Swamps are wooded wetlands of the southeastern U.S. that have standing water for the majority of the growing season. The trees found in these swamps are bald cypress, tupelo gum, and water oak.
- Inland Freshwater Marshes include a variety of wetlands that are full of soft-stemmed plants like grasses, rushes, cattails, and water lilies. They can form in isolated depressions such as the "prairie potholes" of the upper Midwest, as fringes around lakes and ponds, or as nearly flat expenses of emergent wetlands such as those found in Everglades National Park. Wet "mountain meadows" are high elevation freshwater wetlands found in mountain regions.
- Riparian Wetlands form on the floodplains of rivers and streams, and are often dry for portions of the growing season. In the southeastern U.S., "bottomland hardwood forests" are the most common type of riparian wetland. In the arid regions of the West, they are common along rivers and springs and often contrast noticeably with the surrounding upland vegetation.
Tidal Wetlands are found along the coasts within reach of the oceans'' tides: Tidal Salt Marshes develop near river mouths, behind barrier islands, in bays, on coastal plains, or in other areas affected by tides and protected from the surf. Typically vegetated by grasses and other salt water plants, they can range from narrow fringes on steep shorelines to nearly flat expanses several miles wide.
- Mangrove Swamps replace tidal salt marshes in subtropical and tropical regions of the world. The word "mangrove" refers to salt-tolerant trees that dominate these wetlands. In the U.S., they are mainly found on the southern tip of Florida and along the coasts of the Hawaiian islands, although small mangrove stands are scattered as far north as Louisiana and Texas.
- Tidal Freshwater Marshes form inland from salt marshes and mangrove swamps, but are still affected by ocean tides. Grasses and floating-leaved aquatic plants typically dominate these wetlands, found in bays, inlets, and along tidal rivers.
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