tamilnadu Wetland
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. exists in our country.
Wetlands are integral to a healthy environment. They help to retain water during dry periods, thus keeping the water table high and relatively stable. During periods of flooding, 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. Nevertheless, the single most important 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.
Ecosystem services offered by wetlands include floodwater storage and control, recharge of aquifers, treatment of waste water and pollution abatement, general water quality improvement, habitats for fish, wildlife and several other animals and plant species, and biological productivity. In addition, wetlands are of high aesthetic and heritage value providing opportunities for recreation, research, and education.
The trade-off between environmental protection and development is most acute in dynamic and complex ecosystems such as wetlands. Wetlands face a range of anthropogenic threats. The chief indirect drivers of change are human population growth around wetlands coupled with growing economic and commercial activities. Major direct threats for inland wetlands are infrastructure development (dams, dykes, road, residential and commercial buildings), land reclamation and over-harvesting. Major indirect ones are aquaculture, agriculture, reduced water flow, depletion of ground and surface water supplies, introduction of invasive alien species, and organic and inorganic pollutants
In India, momentous losses of wetlands have resulted from conversion to industrial, agricultural and various other developments. These have caused hydrological perturbations and its various reverberations, pollution and several after effects. The above threats can also be distinguished as biotic and abiotic pressures as given below.