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.
Definition
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.
Explanation
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.
Wetland functions
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.
Wetland values
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
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.
Wetland conservation
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.
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