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Thursday, December 11, 2008


As defined in terms of physical geography, a wetland is an environment "at the interface between truly terrestrial ecosystems and aquatic systems making them inherently different from each other yet highly dependent on both". In essence, wetlands are ecotones. Wetlands often host considerable biodiversity and endemism. In many locations such as the United Kingdom, Norway and United States they are the subject of conservation efforts and Biodiversity Action Plans.


Hydrologic functions include long term and short term water storage, subsurface water storage, energy dissipation, and moderation of groundwater flow or discharge.

By absorbing the force of strong winds and tides, wetlands protect terrestrial areas adjoining them from storms, floods, and tidal damage.


Nutrient cycling, retention of particulates, removal of imported elements and compounds, and the import and export of organic carbon are all biogeochemical functions of wetlands. Wetlands remove nutrients from surface and ground water by filtering and by converting nutrients to unavailable forms. Denitrification is arguably the most important of these reactions because humans have increased nitrate worldwide by applying fertilizers. Increased nitrate availability can cause eutrophication, but denitrification converts biologically available nitrogen back into nitrogen gas, which is biologically unavailable except to nitrogen fixing bacteria. Denitrification can be detected in many soils, but denitrification is fastest in wetlands soils.

Intertidal wetlands provide an excellent example of invasion, modification and succession. The invasion and succession process is establishment of seagrasses. These help stabilize sediment and increase sediment capture rates. The trapped sediment gradually develops into mud flats. Mud flat organisms become established encouraging other life forms changing the organic composition of the soil.


Wetlands provide a safe and lush environment for many different species of fish, birds, and insects.

Like animals, there are many plant communities that will only survive in the unique environmental conditions of a wetland. In the continental U.S. wetlands account for only 5% of the total land area, but over 30% of the nation's vascular flora occur in wetlands.


Mangroves establish themselves in the shallower water upslope from the mudflats. Mangroves further stabilize sediment and over time increase the soil level. This results in less tidal movement and the development of salt marshes (succession). The salty nature of the soil means it can only be tolerated by special types of grasses e.g. saltbush, rush and sedge. There is also changing species diversity in each succession.

Value to humans

While many of the functions above are directly or indirectly beneficial to humans and society, wetlands are specifically valuable to people as places for recreational and educational activities such as hunting, fishing, camping, and wildlife observation. Wetlands are often filled in to be used by humans for everything from agriculture to parking lots, in part because the economic value of wetlands has only been recognized recently: the shrimp and fish that breed in salt water marshes are generally harvested in deeper water, for example. Humans can maximize the area of healthy, functioning wetlands by minimizing their impacts and by developing management strategies that protect, and where possible rehabilitate those ecosystems at risk.

Wetlands are sometimes deliberately created to help with water reclamation. One example is Green Cay Wetlands in Boynton Beach, Florida, in the United States.

While the U. S. Environmental Protection Agency estimates that human activities are responsible for about 60 percent of methane emissions worldwide, wetlands are among the natural sources. A study by Ohio State University scientists suggests that river floods and storms that send water surging through swamps and marshes near rivers and coastal areas might cut in half the average greenhouse gas emissions from those affected wetlands.


By 1993 half the world wetlands had been drained.

Protection and rehabilitation

Historically, humans have made large-scale efforts to drain wetlands for development or to flood them for use as recreational lakes. Since the 1970s, more focus has been put on preserving wetlands for their natural function—sometimes also at great expense. One example is the project by the U.S. Army Corps of Engineers to control flooding and enhance development by taming the Everglades, a project which has now been reversed to restore much of the wetlands as a natural habitat and method of flood control.

The creation of the treaty known as the Ramsar Convention (1971), or more properly "The Convention on Wetlands of International Importance, especially as Waterfowl Habitat", demonstrates the global concern regarding wetland loss and degradation. The primary purposes of the treaty are to list wetlands of international importance and to promote their wise use, with the ultimate goal of preserving the world's wetlands.

Those responsible for the management of wetland areas often facilitate public access to a small, designated area while restricting access to other areas. Provision of defined boardwalks and walkways is a management strategy used to restrict access to vulnerable areas, as is the issuing of permits whilst visiting.
In the past, wetlands were regarded as wastelands. Education campaigns have helped to change public perceptions and foster public support for the wetlands. Because of their location in the catchment area, education programs need to teach about total catchment management programs. Educational programs include guided tours for the general public, school visits, media liaison, and information centers

Wetlands by country

New Zealand

Since European settlement, over 90% of the wetlands in New Zealand have been drained, predominantly to create farmland. Wetlands now have a degree of protection under the Resource Management Act.

United States

Wetlands of the United States are defined by the United States Army Corps of Engineers and the United States Environmental Protection Agency as "those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetations typically adapted for life in saturated soils. Wetlands generally include swamps, marshes, bogs, and similar areas.

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