Wetlands include a wide variety of habitats such as marshes, peatlands, floodplains, rivers and lakes, and coastal areas such as saltmarshes, mangroves, and seagrass beds, but also coral reefs and other marine areas no deeper than six metres at low tide, as well as human-made wetlands such as waste-water treatment ponds and reservoirs.
The Convention on Wetlands is an intergovernmental treaty adopted on 2 February 1971 in the Iranian city of Ramsar. Thus, though nowadays the name of the Convention is usually written ‘Convention on Wetlands (Ramsar, Iran, 1971)’, it has come to be known popularly as the ‘Ramsar Convention’. Its mission is ‘the conservation and wise use of all wetlands through local, regional and national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world.
As of December 2006, 153 nations have joined the Ramsar Convention as Contracting Parties, and more than 1600 wetlands around the world, covering over 145 million hectares (larger than the surface area of France, Germany, Spain, and Switzerland combined), have been designated for inclusion in the Ramsar List of Wetlands of International Importance. Five major wetland types are generally recognized:
marine (coastal wetlands including coastal lagoons, rocky shores, and coral reefs)
estuarine (including deltas, tidal marshes, and mangrove swamps)
lacustrine (wetlands associated with lakes)
riverine (wetlands along rivers and streams)
palustrine (meaning ‘marshy’ – marshes, swamps and bogs).
How much of the earth’s surface is presently composed of wetlands is not known exactly. The United Nations Environment Programme (UNEP)-World Conservation Monitoring Centre has suggested an estimate of about 5.7 million km2 – roughly 6% of the Earth’s land surface – of which 2% are lakes, 30% bogs, 26% fens, 20% swamps, and 15% floodplains.
Wetlands are among the world’s most productive environments. They are cradles of biological diversity, providing the water and primary productivity upon which countless species of plants and animals depend for survival. They support high concentrations of birds, mammals, reptiles, amphibians, fish and invertebrate species. Wetlands are also important storehouses of plant genetic material.
Some recent studies have indicated that ecosystems provide at least US$ 33 trillion worth of services annually, of which about US$ 4.9 trillion are attributed to wetlands.
Wetlands contain only 10% of the water found in lakes and other surface waters.
Wetlands act as sponges, absorbing excess water in times of heavy rain and high tides and releasing water slowly during dry periods.
An often quoted estimate is that about 50% of the wetlands that existed in 1900 had been lost by the late 1990s as a result of the conversion of land to agriculture.
Given high population densities, increased rates of deforestation (particularly in Indonesia) and the large degree of ecosystem fragmentation in India, which has more than 4,000 dams, Southeast Asia’s wetlands are probably the most degraded in the world.