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. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, 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. Wetlands occur naturally on every continent except Antarctica, the largest including the Amazon River basin, the West Siberian Plain, and the Pantanal in South America. 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 and they also play a role in water-sensitive urban design.
There are two types of mire – fens and bogs. A bog is a domed-shaped land form, is higher than the surrounding landscape, and obtains most of its water from rainfall (i.e., is ombrotrophic) while a fen is located on a slope, flat, or depression and gets its water from both rainfall and surface water.
Also, while a bog is always acidic and nutrient-poor, a fen may be either slightly acidic, neutral or alkaline and either nutrient-poor or nutrient-rich. A mire is distinguished from a swamp by its lack of a forest canopy (though some bogs may support limited tree or bush growth, mires are dominated by grass and mosses), and from a marsh by its water nutrients and distribution (marshes are characterized by nutrient-rich stagnant or slow-moving waters; mire waters are located mostly below the soil surface level) as well as its plant life (marsh plants are generally submerged or floating-leaved; those in a mire are not). ( Full article...)
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