Facts and figures about wetlands

Under the text of the Ramsar Convention, wetlands are defined as: ‘areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres’.


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 as the ‘Ramsar Convention’. The original emphasis of the Convention was on the conservation and wise use of wetlands with the primary goal of providing habitats for waterbirds. Over the years, however, the Convention has broadened its scope to cover all aspects of wetland conservation and wise use, recognizing wetlands as ecosystems that are extremely important for biodiversity conservation in general and for the well-being of human communities.
Wetlands capture and retain rainfall, and prevent valuable sediments from being washed into lakes and rivers. They add moisture to the atmosphere, which falls as rain and cools the environment.

A global review of wetland resources submitted to the Conference of the Parties to the Convention on Wetlands in 1999, while affirming that ‘it is not possible to provide an acceptable figure of the areal extent of wetlands at a global scale,’ indicated a ‘best’ minimum global estimate at between 748 and 778 million hectares.

The 3 largest wetlands in the world by area are those of the West Siberian Lowlands (780,000-1,000,000 km2), the Amazon River (800,000 km2) and the Hudson Bay Lowlands (200,000-320,000 km2).

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.

Some recent economic studies have indicated that ecosystems provide at least US$ 33 trillion worth of services annually, of which US$ 4.9 trillion are attributed to wetlands.

Humans have damaged wetlands by damming, dyking and canalizing rivers, converting floodplains to aquaculture, planting trees on bogs, draining marshes for agriculture, forestry and urban development and ‘mining’ them for peat, often with heavy state subsidy. But throughout history, agricultural activity has been the most important single cause of damage, with wetlands drained to provide croplands.

50% of the world’s wetlands have been lost in the past century alone.

Information from:
Information Paper No. 1 ‘What are wetlands?’ of the Ramsar Info Pack
Information Paper No. 2 ‘What is the Ramsar Convention on Wetlands?’ of the Ramsar Info Pack
the ‘Freshwater Resources’ section from the Vital Water Graphics website
the UNESCO’s New Courier article ‘Save that swamp!’
the Freshwater Wetlands section of the Atlas of Population and Environment by the American Association for the Advancement of Science

Source: UNESCO Water Portal, January 2006

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