Extent, regional distribution and changes in area of different classes of wetland

Abstract

We compiled available data and information on the global and regional areas (Ramsar regions), and changes in area, of 22 classes of marine or coastal and inland wetlands. From those classes for which there is information, inland natural surface wetlands (forming ~77% of total surface wetland extent) are dominated by non-forested peatlands, marshes and swamps on alluvial soils, with peatlands forming ~33% of natural inland wetlands. The smaller area of marine or coastal wetlands (~10% of total wetland extent) is dominated by unvegetated tidal flats and saltmarshes. Largest areas of human-made wetlands for which there is information are rice paddy and water storage bodies, with a much smaller area of tropical oil palm and pulpwood plantations. These human-made wetlands are all increasing in area. The reported decline in global natural wetland area is occurring across almost all classes of inland and marine or coastal natural wetlands. Total global wetland area estimated from these wetland classes is between 15.2×106 and 16.2×106km2, similar to recent global wetland area estimates derived from remote sensing. Given the considerable data gaps for area of wetland classes, even the most recent other estimates of global wetland extent are likely to be underestimates.