Wetlands of South Asia

Abstract

The Indian subcontinent is a natural biogeographic region. Wetlands occur in all climatic zones but a large majority of them are aseasonal in nature due to long dry summer periods. A scheme of wetland classification is proposed to group them into saline and freshwater wetlands and categorise them further according to hydrological factors and vegetation types. Among saline wetlands, mangroves which are coastal and estuarine forested wetlands, are among the world's largest such formations. There are also saline and estuarine shallow lakes and temporarily flooded scrublands. Frequent cyclones and reduced freshwater flows due to river regulation are important factors causing degradation of these wetlands. Freshwater wetlands are dominated by shallow lakes, ponds, and temporary water bodies which become periodically dry. Permanent herbaceous wetlands and forested swamps occur mostly in the sub-Himalayan tract. Seasonal wetlands have a large variety of submerged, floating leaved and emergent vegetation. These wetlands have become infested with exotic free-floating water hyacinth Eichhornia crassipes. Extensive floodplain wetlands occur along all major and medium rivers. Most freshwater wetlands have been converted into paddy fields and fish ponds, and the remaining are being rapidly lost or degraded by filling, drainage, disposal of sewage and industrial effluents. -from Authors