Saroar M. Mustafa
Concept, Types and Status of Wetlands in Bangladesh:
The Ramsar Convention (1971) has defined wetlands as - areas of marsh, fen, peat-land, 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 metres. The Ramsar definition of wetlands lumps together a wide range of contrasting habitats like fluvial, coastal and marine. Nevertheless, the Ramsar definition has been adopted and being used in Bangladesh. Wetlands of Bangladesh are classified on the basis of their hydrological and ecological functions and land types. Broadly wetland in Bangladesh is divided into estuarine and freshwater systems, which again further subdivided by soil type and plant life. Thus wetlands include areas of marsh, fen, bog, flood plain, and shallow coastal areas. Wetland area is characterized by sluggish or standing water that can create an open water habitat for wildlife.
As I mentioned earlier wetlands in Bangladesh are represented by both inland freshwater and estuarine/tidal salt-water wetlands. Flood plains, beels (low-lying depressions in the flood plain), haors and baors (oxbow lakes) represent the inland freshwater wetlands (Khan et al. 1994). The haors are bowl-shaped natural depressions between the natural levees of the river subject to monsoonal flooding every year. While the haor itself is a seasonal water body formed during the monsoon, the beels are low-lying depressions of the haor system retaining water even during the dry months of the season. Thus, the haor system is a complex of both lacustrine and palustrine wetlands depending on the hydraulic behavior in different seasons. The ecology of the haor system is principally driven by seasonal hydraulics. During the monsoon, the entire haor system becomes a single body of open water linked to the river system. When floodwater recedes, the beels become isolated and remain as standing water bodies till the next rainy season. They differ from a true lake system in that the main source of waters in tropical lakes is rainwater, while a haor system depends on both precipitation and floodwater as sources of water.
Estuarine/tidal salt-water wetlands constitute about 25 per cent of the land area and are represented by mangroves, salt marsh, lagoons, deltaic islands, sand dunes and beaches, barrier islands, sea grass and coral habitats.
In the following table major types of wetlands of Bangladesh are presented.
1.Saltwater wetlandsa) Marine permanent shallow waters at low tide, eg bay coral reefs, eg St Martin's reef b) Estuarine intertidal mud, sand or salt flats with limited vegetation, eg newly-accreted land intertidal marshes intertidal forest wetlands including mangroves, eg Sundarbans c) Lagoonal brackish to saline lagoons with narrow connection with sea 2.Freshwater wetlandsa) Riverine wetlands permanent rivers and streams including some char land, temporary seasonal rivers and streams b) Lacustrine wetlands There are thousands of lakes of varying sizes in Bangladesh, the greatest concentrations being in the main delta region covering the districts of Rajshahi, Pabna, Khulna, Jessore, Faridpur, Comilla and Noakhali. c) Palustrine wetlands permanent freshwater marshes and swamps with emergent vegetation, permanent peat-forming freshwater swamps, freshwater swamp forest, eg hijal forests of lowland 3.Man-made wetlands aquaculture ponds (brackish and freshwater) irrigated land and irrigation channels salt pans hydro-dam, eg Kaptai Lake
However, the areal extent of wetlands in the above classification is not available. A different classification is show to give idea about the wetland in Bangladesh which is rather indicative than exact as primarily because size of each wetland varies depending on season; Monsoon,...