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Wetlands

Losses Of Wetlands

All wetlands have great intrinsic value as natural ecosystems, and they all support species of plants and animals that occur nowhere else. Consequently, wetlands have great value in terms of biodiversity.

Sometimes, the biodiversity-related importance of particular types of wetlands is a matter of their relative abundance, in the regional context. For example, although bogs and fens can be extremely abundant in boreal and sub-arctic regions of northern North America, these types of wetlands are uncommon farther south, where they usually occur as relict, post-glacial ecosystems. In these southern regions, the few bogs and fens that occur have great conservation value as scarce and unusual ecosystems, and because most of their species of plants and arthropods are regionally or locally rare. As such, any proposals to "develop" these wetlands into agricultural or urbanized lands are highly controversial, because these conversions would cause an irretrievable loss of natural values.

Wetlands also provide essential habitat for species of birds and mammals that are hunted, and this gives them economic value. Waterfowl such as ducks and geese occur primarily in marshes and swamps. During the past century the populations of some of these hunted waterfowl were greatly decreased, as a combined effect of overhunting and loss of natural habitats. Consequently, there are now substantial efforts to regulate hunting, and to preserve or enhance the marshes and swamps that are required as habitat by these birds. Some species of waterfowl are responding well to these conservation measures, and their populations are increasing.

Wetlands are also important because they offer other ecological goods and services, in addition to those previously described. For example, wetlands maintain some control over hydrology, helping to prevent extremes of water flow. This service moderates the risks of flooding caused by heavy rain or the spring flush of snowmelt in northern regions. It also helps to extend supplies of water for drinking or irrigation longer into the drier seasons of the year. Wetlands also provide important services by cleansing the water that flows through them of pollutants, including nutrients and toxic chemicals, such as metals and certain pesticides. Furthermore, wetlands are useful in protecting shorelines from erosion, controlling sedimentation, and providing essential habitat for fish, birds, and other wildlife. Wetlands have good aesthetics, and this also contributes to their value as an ecological resource.

Unfortunately, wetlands are being rapidly lost in most of the world. The most important causes of the destruction of wetlands are drainage and in-filling to provide dry land for agriculture, urbanization, and industrialization. Wetlands are also sometimes used as convenient places for the disposal of mine tailings, municipal solid wastes, and sewage. In some cases, wetlands are degraded or lost because economically useful products can be mined from them, especially peat from bogs, and wood from forested swamps. Wetlands are also degraded if they are subjected to large inputs of nutrients through the runoff of agricultural fertilizers or by sewage dumping. These nutrient inputs can cause eutrophication, with a consequent loss of the original ecological values of the wetland.

All of these disturbances, stresses, and ecological conversions result in net losses of wetlands. The ecological consequences include endangerment of natural wetland ecosystems, endangerment of their species of plants and animals, and the loss of many important services that wetlands can provide. The loss of wetlands is an important environmental issue, which can only be resolved by protection of those wetlands that still survive, and in some areas where the losses have been especially severe, by the active restoration of wetlands.

The protection and conservation of wetlands is an important activity of many governments and private organizations. In the United States and Canada, wetlands are among the highest-priority natural habitats for protection by governments at all levels (national, state or provincial, and local). In addition, non-governmental organizations such as the World Wildlife Fund, The Nature Conservancy, the Nature Conservancy of Canada, and Ducks Unlimited have made the conservation and protection of wetlands a high priority in their activities. Internationally, the Convention on Wetlands of International Importance, Especially as Waterfowl Habitat (also known as the Ramsar Convention, after the city in Iran where it was negotiated) is an intergovernmental treaty that provides a framework for worldwide cooperation in the conservation of wetlands. The activities of all of these agencies are important and useful, but much more needs to be done to give wetlands and their species the degree of protection that they require.

Resources

Books

Barbour, M.G., and W.D. Billings. North American Terrestrial Vegetation. Cambridge: Cambridge University Press, 1988.

Barbour, M.G., J.H. Burk, and W.D. Pitts. Terrestrial Plant Ecology, 2nd ed. Ontario: Benjamin/Cummings Pub. Co., Don Mills, 1987.

Finlayson, M., and M. Moser. Wetlands. New York: Facts on File, 1991.

Hamblin, W.K., and E.H. Christiansen. Earth's Dynamic Systems. 9th ed. Upper Saddle River: Prentice Hall, 2001.

Hancock, P. L., and B. J. Skinner, eds. The Oxford Companion to the Earth. Oxford: Oxford University Press, 2000.

Mitsch, W.J., and J.G. Gosselink. Wetlands. John Wiley and Sons, 1997

Sobel, Jack. Marine Reserves: A Guide to Science, Design, and Use. Washington, DC: Island Press, 2003.

Vileisis, A. Discovering the Unknown Landscape: A History of America's Wetlands. Island Press, 1997

Periodicals

"Satellite Remote Sensing of Wetlands." Wetlands Ecology And Management 10, no. 5-5 (2002): 381-402.


Bill Freedman

KEY TERMS

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Alkalinity

—The amount of alkali in a solution. In fresh water, alkalinity is mainly associated with bicarbonates, carbonates, and hydroxides, and it is generally measured by titration with acid to a fixed end point.

Anaerobic

—Environments in which oxygen is not present, or only present in a very small concentration.

Eutrophication

—An aquatic ecosystem process by which increased productivity results from an increase in the rate of nutrient input. Excessive eutrophication and its symptoms are regarded as a type of ecological degradation.

Graminoid

—A generic term for plants with a grass-like growth form, such as grasses (Poaceae), sedges (Cyperaceae), rushes (Juncaceae), and cattails (Typhaceae).

Hydrology

—The study of the distribution, movement, and physical-chemical properties of water in Earth's atmosphere, surface, and near-surface crust.

Minerotrophic

—This refers to wetlands that receive much of their nutrient supply as substances dissolved in water draining from a part of the watershed that is higher in altitude.

Ombrotrophic

—This refers to wetlands with no input of nutrients from ground water or surface water, so that all of the nutrient supply arrives from the atmosphere with precipitation and dust.

Watershed

—The expanse of terrain from which water flows into a wetland, waterbody, or stream.

Additional topics

Science EncyclopediaScience & Philosophy: Well-being to Jan Ɓukasiewicz BiographyWetlands - Swamps, Marshes, Shallow Open Water, Fens, Bogs, Wetland Ecology, Losses Of Wetlands - Types of wetlands