Wetlands are areas of land that are a combination of terrestrial and aquatic ecosystems. Inland wetlands include creeks, swamps, marshes, and shallow aquifers while coastal wetlands include estuaries, tidal basins, marshes, deltas and mangroves. These water covered areas are biologically diverse and provide a habitat for a wide variety of fish, amphibians, water fowl and other birds, insects, and mammals.
In addition to their role as a productive habitat, wetlands also play an important role in the larger ecosystem. Because of their dense aquatic and semi-aquatic vegetation and thick mud, wetlands act as a filter, purifying water that passes through them. Water containing pollution such as nitrogen and phosphorus from fertilizers and agricultural runoff, and heavy metals from industrial waste is filtered and detoxified by passing through wetlands. Wetlands also mitigate floods, direct river flow, reduce erosion, and sequester carbon which helps to regulate the climate. There are estimates that the monetary value of the services that wetlands provide is as high as US$14.9 trillion.
In 1971, the Ramsar Convention was signed to recognize the value of wetlands and to promote ecologically sustainable management of these areas. As of October, 2006 there are currently 1,629 Ramsar sites on the Ramsar List of Wetlands of International Importance and 153 contracting parties to the Ramsar Convention.
Map of Wetlands, Dams, and Ramsar Sites in Africa [Source: World Resources Institute]
The high levels of biodiversity and natural beauty of many wetlands attract tourism. The economic benefit of this tourism is significant. In 1996, the Ramsar Convention Bureau stated that in the United States, five million Americans spend more than US$638 million a year visiting waterfowl refuges and that wildlife safaris in Botswana’s Okavango Delta (the world’s largest Ramsar site) are worth about US$13 million a year.
Unfortunately, many wetlands are facing environmental degradation. Threats to wetlands include climate change, pollution from agriculture and industrial manufacturing, and development. While wetlands have the ability to filter and detoxify pollutants, there is a threshold for pollution tolerance, beyond which wetlands die out and become areas of concentrated contamination. The practice of drying out and filling in wetlands to convert them to developable land or draining them for agricultural use destroys wetland ecosystems, and harms the larger ecosystems of which they are an integral part.
EarthTrends has more information on wetlands, including data, maps and feature articles:
Watersheds of the World is EarthTrends’ collection of watershed maps and profiles.
Some helpful EarthTrends features are Freshwater Biodiversity in Crisis and Nutrient overload: Unbalancing the global nitrogen cycle.
Wetland related variables include:
Industrial Water Pollution: Organic water pollutant (BOD) emissions
Ecosystem Area: Permanent wetlands
Protected Areas: Wetlands of international importance (Ramsar sites), number
Multilateral Agreements Status: Ramsar Convention (wetlands)
Other websites that provide useful information on wetlands include:
The Ramsar Convention on Wetlands
Vital Water Graphics -- UNEP/GRID-Arendal
A great report on the current status of wetlands is the Millennium Ecosystem Assessment synthesis report on wetlands: Ecosystem Services and Human Well-being: Wetlands and Water Synthesis
