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Why are Wetlands Important?

Click here to view full size picture The following information is from Living With Michigan's Wetlands: A Landowner's Guide, copyright 1996, Tip of the Mitt Watershed Council

Species Habitat
Fish and Wildlife Habitat
Water Pollution Control
Sediment Control
Erosion Control
Prevent Flooding

Species Habitat

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Not surprisingly, wetland habitats are critical for the survival of threatened or endangered species. Endangered species are those that are in danger of becoming extinct. Threatened species are those that are in danger of becoming endangered. These species represent a unique element of Michigan's valuable natural heritage. More than one-third of all threatened or endangered animal species in the United States are either located in wetland areas or depend on them. This is especially critical considering that wetlands comprise only about five percent of the land mass of the lower 48 United States. Examples of Michigan's threatened or endangered animals that rely on wetlands include the Bald Eagle, Osprey, Common Loon, and King Rail. Of Michigan's total 395 threatened, endangered, rare, and special concern plant species, 194 of them are found in wetland habitats. Thus, nearly 50% of Michigan's plants of management concern reside in less than 15% of Michigan's surface area. Click here to view full size picture

Fish and Wildlife Habitat

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Fish and wildlife habitat is the most widely celebrated and actively enjoyed wetland function. Many landowners own their wetlands solely for the benefits derived from this function. Some species spend their entire lives in wetlands, others utilize them intermittently for breeding or rearing their young. Simply put, wetlands provide critical habitat for Michigan's wildlife.

Most freshwater fish are considered wetland dependent. Fish feed in wetlands or on food produced there. Wetlands serve as nursery grounds for many species whose young take cover there, and many important sport fishes spawn in or near wetlands.

Like fish, many bird species are dependent on wetlands. Birds use wetlands for migratory resting places, breeding or feeding grounds, or taking cover from predators. It is estimated that over one-third of all bird species in north America rely on wetlands for one of these purposes.

Nearly all of Michigan's amphibians are wetland dependent, at least for breeding. Amphibians are sensitive to changes in wetland quality and quantity. Many scientists correlate declines in amphibian populations with wetland degradation worldwide.

Wetlands serve as the preferred habitat for many fur bearing animals such as muskrat, beaver, otter, mink and raccoon. In northern Michigan, cedar swamps are critical to white-tailed deer for many reasons, including winter browse (northern white cedar sustains deer in the absence of other foods) and important thermal cover during harsh winters.
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Water Pollution Control

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A major function of wetlands is water quality protection. Wetlands function like living filters by removing polluting nutrients and sediments from surface and ground water. Although less well-known than providing fish and wildlife habitat, this wetland function is important to landowners and their communities.

Excess inputs of nutrients such as phosphorus and nitrogen can cause severe problems in aquatic ecosystems. You might say, "I thought nutrients were good." Nutrients such as phosphorus are necessary, but can be a classic example of how "too much of a good thing is bad." Excess nutrients can cause an undesirable increase in algae and aquatic plant growth. The result is water that is reminiscent of pea soup, weed-choked lakes, depleted dissolved oxygen levels, and the rapid aging or "eutrophication" of a lake. The massive algae blooms and depleted dissolved oxygen levels of Lake Erie in the early 1970's is a classic example of what happens to an aquatic system under the strain of too many nutrients.

Wetlands retain or remove nutrients in four ways: 1) uptake by plant life, 2) adsorption into sediments, 3) deposition of detritus (organic materials), and 4) chemical precipitation. The most significant of these are the uptake of nutrients by plants (which occurs primarily during the growing season, the same time that lakes and streams are most sensitive to nutrient inputs) and adsorption into sediments.
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Sediment Control

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As sediment-laden water flows through a wetland from the surrounding watershed, the sediments are deposited into the wetland. This reduces siltation into lakes, rivers, and streams. A combination of wetland vegetation and generally flat topography serves to slow water flow and increase deposition of silt and organic matter. Because of the soil chemistry in wetlands, carbon compounds that are deposited in wetlands decompose very slowly. In this manner, wetlands serve as a relatively permanent resting place for carbon compounds. This function of wetlands can help to trap carbon that would otherwise accumulate in the upper atmosphere and contribute to global climate change. Furthermore, there is a strong tendency for heavy metals and other toxic chemicals to attach to the sediment particles found in surface water runoff. Wetlands can trap these human-induced pollutants and remove them from the water column. However, when the natural ability of wetlands to function as filters is overstressed from human inputs, the wetland and its functions can be destroyed. In fact, when overloaded, wetlands can actually become sources of pollutants, exporting materials that have been filtered and stored for centuries.

Erosion Control

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In their natural condition, wetlands function as a barrier to erosion. The root systems of wetland plants stabilize soil at the water's edge and enhance soil accumulation at the shoreline. Wetland vegetation along shorelines reduces erosion by dampening wave action and slowing current speed.

Prevent Flooding

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Wetlands act as a hydrologic sponge, temporarily storing flood waters and releasing them slowly, thus reducing flood peaks and protecting downsteam property owners from flood damage. Wetlands and adjacent floodplains often form natural floodways that convey flood waters from upland to downsteam points. These functions become increasingly important in urban areas where development has increased the rate and volume of runoff.
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