Wetlands are among the most important ecosystems on earth. Wetlands generally include swamps, marshes, bogs and similar areas. Wetlands are everywhere from the tundra to the tropics. The UNEP – World Conservation Monitoring Centre has suggested an estimate of about 570 million hectares-roughly 6% of the earth’s land surface – of which 2% are lakes, 30% bogs, 26% fens, 20% swamps and 15% floodplains. They have been valuable as sources, sinks and transformers of a multitude of chemical, biological and genetic materials. They have been found to cleanse polluted waters, protect shorelines and recharge ground water aquifers. They play a major role in the landscape for providing unique habitats for a wide variety of plants and animals. Wetlands are important carbon sinks and climate stabilizers on a global scale. Though wetlands cover a small are on the surface of the earth, but contain around 35% of the global terrestrial carbon. Wetlands act as sinks for carbon dioxide and other greenhouse gases (GHGs). Wetlands can remove from 70 to 90% of nitrates from the environment.
The land, where an excess of water is the dominant factor determining the nature of soil development and the types of animal and plant communities living at the soil surface. Wetland spans a continuum of environments where terrestrial and aquatic systems intergrade.
This definition includes three aspects such as hydrology, hydric soil and hydrophytes. Wetlands predominantly have undrained hydric soils with prolonged water saturation and low oxygen content which leads to anaerobic chemical environment. Wetlands predominantly have specialized vegetation such moss, sedges, reeds, cattail, and horsetail, rice, mangroves and cypress. The root zone consists of peat saturated with water.
Types of wetlands
Wetlands may be natural or artificial, permanent or temporary, with water static or flowing, fresh, brackish or salt water. There are 5 kinds of wetland systems (Schot, 1999).
1. Marine – (coastal wetlands)-coastal lagoons, rocky shores and shallow coral reefs.
2. Estuaries – deltas, tidal marshes, mudflats and mangrove swamps.
3. Riverine – (wetlands along rivers and streams)-floodplains.
4. Lacustrine – (wetlands associated with lakes) – reed beds, dammed river channel.
5. Palustrine- (meaning marshy, non-tidal wetlands) – marshes, swamps and bogs.
Wetlands can also be grouped as marine and coastal wetlands, inland wetlands and human-made wetlands. The human- made wetlands include fish and shrimp ponds, farm ponds, irrigated agricultural lands, salt pans, reservoirs, gravel pits, sewage farms and canals.
A water filtering system –wetlands filter and purify water. They remove contaminants, suspended solids and excessive nutrients from runoff or storm waters- “The kidneys of the landscape.”
A habitat for variety of organisms – It is a home for many special plants, migratory birds, fish and frogs. It is a nesting, feeding and staging ground for water birds, reptiles and amphibians. It is a spawning and nursery grounds for many species of fish. Wetlands support extensive food chain and rich biodiversity –“Ecological supermarkets.” They are a habitat for some species of threatened fauna.
A reservoir for water storage – wetlands support agricultural activities by providing a source of water for irrigation and livestock and for domestic consumption. Wetlands provide a natural water balance in the landscape.
A source of oxygen and water vapour – wetlands play a vital role in natural atmospheric and climate cycles.
A barrier for erosion and flood control – wetlands slow down runoff water and control the erosive forces of moving water along lakes and steam banks. Wetlands reduce the risk of flooding. Wetlands support sustainable forestry.
A venue for research and education – wetlands provide opportunities for scientific research and are a source of education for the community.
A popular location for tourism and recreational activities – wetlands provide wild environment for hiking, bird watching, and fishing, swimming and boating.
Wetlands provide tremendous economic benefits such as water supply, fisheries, agriculture, energy resources, wildlife resources, transport, and tourism opportunities. Wetlands are the most productive ecosystems on earth. They are the cradles of biological diversity and storehouse of plant genetic material particularly rice. They are essential for the health, welfare and safety of people, who live in or near them.
Wetland loss is the loss of wetland area and wetland degradation is the impairment of wetland functions. Some estimates show that the world may have lost 50% of the wetlands that existed since 1900. Similarly U.S also lost nearly 50% of its wetland resources, since 1700s. Approximately 85% of the Asian wetlands are threatened (Scott and Carbonell, 1985). Based on Ramsar database, 84% of the wetlands are threatened by global ecological change. Drainage for agricultural production is the principal cause of wetland loss. It was estimated that 56-65% of the available wetland had been drained for intensive agriculture in Europe and North America (1985 data). The figures for tropical and subtropical regions were 27% for Asia, 6% for South America and 2% for Africa, making a total of 26% worldwide.
The convention on wetlands was signed in Ramsar, Iran in 1971 called The Ramsar convention on wetlands. The Ramsar convention is an intergovernmental treaty, which provides the framework for national action and intergovernmental cooperation for the conservation and wise use of wetlands and their resources. The Government of India instituted National Wetland Conservation Programme (NWCP) in the year 1985-86 to lay down policy guidelines for the conservation and management of wetlands in the country.