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A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem.〔(【引用サイトリンク】 publisher = State of Florida )〕 The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants,〔 〕〔(【引用サイトリンク】 accessdate = 2011-09-25 )〕 adapted to the unique hydric soil. Wetlands play a number of roles in the environment, principally water purification, flood control, carbon sink and shoreline stability. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life.〔(【引用サイトリンク】 accessdate = 2011-09-25 )〕 Wetlands occur naturally on every continent except Antarctica,〔(【引用サイトリンク】 accessdate = 2011-09-25 )〕 the largest including the Amazon River basin, the West Siberian Plain, and the Pantanal in South America.〔(【引用サイトリンク】 accessdate = 2011-09-25 )〕 The water found in wetlands can be freshwater, brackish, or saltwater.〔 The main wetland types include swamps, marshes, bogs, and fens;〔 〕 and sub-types include mangrove, carr, pocosin, and varzea. The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. International conservation efforts are being used in conjunction with the development of rapid assessment tools to inform people about wetland issues. Constructed wetlands can be used to treat municipal and industrial wastewater as well as stormwater runoff, They may also play a role in water-sensitive urban design. ==Definitions== A patch of land that develops pools of water after a rain storm would not be considered a "wetland," even though the land is wet. Wetlands have unique characteristics: they are generally distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. Specifically, wetlands are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants.〔(【引用サイトリンク】title=Glossary )〕 A more concise definition is a community composed of hydric soil and hydrophytes.〔 Wetlands have also been described as ecotones, providing a transition between dry land and water bodies.〔(【引用サイトリンク】title=Glossary )〕 Mitsch and Gosselink write that wetlands exist "...at the interface between truly terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet highly dependent on both." In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「wetland」の詳細全文を読む スポンサード リンク
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