A Wetland is a distinct ecosystem where the land is covered by water, either salt or fresh or somewhere inbetween. It exists all around the world from polar to tropical region and high altitudes to dry regions.Wetlands are the ecotones or transitional zones between permanently aquatic and dry terrestrial ecosystems. Ramsar Convention has defined wetlands 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 meters”. A wide variety of wetlands like marshes, swamps, open water bodies, mangroves and tidal flats and salt marshes etc. exist in our country
Wetlands are areas where water is the primary factor controlling the environment and the associated plant and animal life.Wetlands are integral to a healthy environment. They help to retain water during dry periods, thus keeping the water table high and relatively stable. At the time of flood, they act to reduce flood levels and to trap suspended solids and nutrients to the lakes than if they flow directly into the lakes. Compared to tropical rain forests and coral reefs, wetlands are remarkable in their biological productivity. With respect to species richness and species diversity, these ecosystems stand higher than most other ecosystems. Wetlands are diverse and unique in structure, characteristics and functions, probably much more than other ecosystems. Wetlands are dynamic and complex and are under the influence of an array of biotic and abiotic factors. The most significant factor that determines the nature of a wetland is its hydrologic regime. Even for minor changes in the hydrologic regime of wetlands, biota may respond at times markedly in terms of species composition, richness, trophic relations and ecosystem productivity.