Wetlands

Wetlands are the major contributors to global biodiversity. They contribute more than 20% of the world's taxa and genetic resources although occupying only about 6% of the world's surface. Wetland is defined as submerged or water saturated land, the depth of water being less than six meters for the major portion of the year. Such areas include swamps, marshes, fens, peat lands, lagoons, lakes etc. Ecologically, wetlands are important eco-tones endowed with definite structural and functional attributes and specific ecological roles.

Wetlands have been variously described as "kidneys of the landscape", and "biological supermarkets". They provide unique habitats for a wide variety of flora and fauna including thousands of migratory waterfowl.

Wetlands are among the most threatened ecosystems being subjected to severe anthropogenic pressure. Industrial effluents, intensive aquaculture, excessive use of chemical fertilisers and pesticides in agriculture pollute the down stream wetlands. Fishing is an important activity in fresh water lakes, large rivers and estuaries. Human dependence on wetlands is high, and human settlements are concentrated near the sea coasts and shores of lakes or rivers in order to take advantage of the range of benefits that wetlands provide.

The importance of the wetlands is on account of their role in:-

- flood control,
- water storage and purification,
- protection of shorelines and hinterlands,
- habitat for varieties of flora and fauna
- economic sustenance to the people,
- recreational facilities, etc.

Orissa is endowed with a variety of wetland types including mangrove swamps, lakes and reservoirs, estuaries, mudflats, marshes, etc. Because of the State's extensive coast line (over 480 km length) coastal wetland types are more prominent. Other types are also well represented, such as freshwater swamps and marshes, river basins, reservoirs and dams, lakes, lagoons, etc.

Mangrove swamps:

The river systems draining into the Bay of Bengal form extensive deltas which support mangrove forests. The mangrove forests occur over six river deltas, namely Subarnarekha, Budhabalanga, Brahmani, Baitarani, Mahanadi and Devi and cover total area of 219sq.km. The Bhitarkanika area (a Sanctuary/National Park) in Brahmani-Baitarani delta is the largest (150 sq.km approx.) compact block of mangroves and harbours India's richest mangrove forest in terms of species diversity. The diverse climatic condition of mangrove wetlands provide ideal habitat for a variety of invertebrate and vertebrate fauna (lizards, snakes, Saltwater crocodiles, varieties of waterfowl, mammalian species, etc.). Mangroves in other river mouth areas are degraded by a variety of impacts, the most significant of which is conversion to brackish water fish ponds, or to paddy cultivation.

Estuaries are semi-enclosed water bodies which have connections to the sea and in which sea water is diluted by freshwater from land drainage. Estuaries are high productive areas because of the nutrients which they receive from the land and the sheltered environments that they provide. Extensive mudflats are often associated with the estuaries.

The river basins include small, medium and large, of which Mahanadi basin is the largest.

A large number of swamps and marshes are seen all over the state because of the extensive network of six major rivers and the location of the state close to Bay of Bengal.

There are a number of small, medium and large reservoirs in the state. Hirakud in Sambalpur district and Balimela in Maikangiri are two large reservoirs.

Chilika and Anshupa are two well known lakes of the state. The former is a brackishwater lagoon while the latter is a dying freshwater lake close to river Mahanadi in Athgarh sub-Division of Cuttack district.

In February, 1971, in the Iranian city of Ramsar, an important inter-governmental treaty on wetlands was adopted. It is a global treaty on conservation of wetland resources, and is popularly known as the 'Ramsar Convention'. While initially there was emphasis on providing habitat for water birds, over the years, the scope of the Convention has broadened to cover the entire range of issues on use of Wetlands. The Convention came into force in 1975. India joined the convention in 1982. Nineteen wetlands from the entire country have been designated Ramsar sites including Chilika and Bhitarkanika from Orissa state.