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.
This is a woodland that occurs on poorly drained or seasonally wet soils. They are typical of river valley, the surroundings of mires and raised bog, the transition zones between open water and drier ground, and beside small winding streams. Alder, birches and willows are the characteristic trees found in this type of habitat, as they are able to extract oxygen from the water saturated habitat. The UK contains between 50–70,000 hectares (120–172,970 acres).
Wet woodland supports many types of species. E.g. the humidity favours bryophytes (mosses). Alder, birch and willows support many invertebrates: the beetles Melanopion minimum and Rhynchaenus testaceus, the craneflies Lipsothrix errans, Lipsothrix nervosa, and mammals such as otters.
In the UK Woodland Maintenance and Restoration grants are available to protect this type of Woodland under Natural England's Environmental Stewardship Scheme.
Within the British National Vegetation Classification seven types of Wet Woodland are recognised as part of the Woodland and scrub communities in the British National Vegetation Classification system. (Full article...)
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