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Sunday, March 27, 2011

Wetlands and their roles in the evironment

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The cycling of nutrients is also performed by wetlands and aquatic plants. These help in the recovery of resources also, since these produce biomass that can be harvested and utilized as a source of energy and food for the efficient recycling of nutrients. Wetlands are instrumental in decreasing both the nutrient load and high biochemical oxygen demand (BOD) levels of the wetlands and Lakes. Different native aquatic plants such as emergent, floating leaved, submerged and free-floating vegetation colonize lakes and wetlands, and are the sources for the formation of different niches occupied by variety of micro flora and fauna. The lake plays a major role in the removal, recycling of nutrients, and also controlling water pollution through physical, chemical and biological means.

Image 1 Wetland-  credit Encyclopedia of Earth

Image 2  wetland with a dependent animal

What are wetlands? Well, Wetlands are marshy areas where there is much moisture in the soil. Wetlands are sometimes covered in water. Swamps, marshes, and bogs are some of the names used for wetlands. In other words, "Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or where water shallow covers the land and where at least one of the following attributes holds-
·         the land predominantly supports aquatic plants at least periodically;
·         untrained hydric soils are the predominant substrate; and
·         at some time during the growing season, the substrate is saturated with water or covered by shallow water." Definition by Environmental Protection Agency, U.S.A.

Ecological Roles of Wetlands
Wetlands are among the most productive ecosystems in the world, comparable torainforests and coral reefs. An immense variety of species of microbes, plants, insects, amphibians, reptiles, birds, fish, and mammals can be part of a wetland ecosystem. Physical and chemical features such as climate, landscape shape (topology), geology, and the movement and abundance of water help to determine the plants and animals that inhabit each wetland. The complex, dynamic relationships among the organisms inhabiting the wetland environment are referred to as food webs.

The functions of a wetland and the values of these functions to human society depend on a complex set of relationships between the wetland and the other ecosystems in the Watershed. A watershed is a geographic area in which water, sediments, and dissolved materials drain from higher elevations to a common low-lying outlet or basin a point on a larger stream, lake, underlying aquifer or estuary.

Wetlands play an integral role in the Ecology of the watershed. The combination of shallow water, high levels of nutrients, and primary productivity is ideal for the development of organisms that form the base of the food web and feed many species of fish, amphibians, shellfish, and insects. Many species of birds and mammals rely on wetlands for food, water, and shelter, especially during migration and breeding.

Wetlands' microbes, plants, and wildlife are part of global cycles for water, nitrogen, and sulfur. Furthermore, scientists are beginning to realize that atmospheric maintenance may be an additional wetlands function. Wetlands store Carbon   within their plant communities and soil instead of releasing it to the atmosphere as carbon dioxide. Thus wetlands help to moderate global climate conditions.

Economic benefits of wetlands
Only recently have we begun to understand the importance of the functions that wetlands perform. Far from being useless, disease-ridden places, wetlands provide values that no other ecosystem can, including natural water quality improvement, flood protection, shoreline erosion control, opportunities for recreation and aesthetic appreciation, and natural products for our use at no cost. Wetlands can provide one or more of these functions. Protecting wetlands in turn can protect our safety and welfare.

Water Quality and Hydrology
Wetlands have important filtering capabilities for intercepting surface water run off   from higher dry land before the runoff reaches open water. As the runoff water passes through, the wetlands retain excess nutrients and some pollutants, and reduce sediment that would clog waterways and affect fish and amphibian egg development. In performing this filtering function, wetlands save us a great deal of money. For example, a 1990 study showed that without the Congaree Bottomland Hardwood Swamp in South Carolina, the area would need a US$5 million waste water treatment plant.

In addition to improving water quality through filtering, some wetlands maintain stream flow during dry periods, and many replenish Ground Water.  Many Americans and yes, most of Indians depend on groundwater for drinking.

Flood Protection
Wetlands function as natural sponges that trap and slowly release surface water, rain, snowmelt, ground water  and flood waters. Trees, root mats, and other wetland vegetation also slow the speeds of flood waters and distribute them more slowly over the floodplain. This combined water storage and braking action lowers flood heights and reduces erosion. Wetlands within and downstream of urban areas are particularly valuable, counteracting the greatly increased rate and volume of surface water runoff from pavement and buildings.

The holding capacity of wetlands helps control floods and prevents water-logging of crops. Preserving and restoring wetlands, together with other water retention, can often provide the level of flood control otherwise provided by expensive dredge operations and levees. The  bottomland hardwood  riparian wetlands along the Mississippi River once stored at least 60 days of floodwater. Now they store only 12 days because most have been filled or drained.

Shoreline Erosion
The ability of wetlands to control erosion is so valuable that some states are restoring wetlands in coastal areas to buffer the storm surges from hurricanes and tropical storms. Wetlands at the margins of lakes, rivers, bays, and the ocean protect shorelines and stream banks against erosion. Wetland plants hold the soil in place with their roots, absorb the energy  of waves, and break up the flow of stream or river currents.

More than one-third of the United States' threatened and endangered species live only in wetlands, and nearly half use wetlands at some point in their lives. Many other animals and plants depend on wetlands for survival.
Estuarine and marine fish and shellfish, various birds, and certain mammals must have coastal wetlands to survive. Most commercial and game fish breed and raise their young in coastal marshes and estuaries. Menhaden, flounder, sea trout, spot, croaker, and striped bass are among the more familiar fish that depend on coastal wetlands. Shrimp, oysters, clams, and blue and Dungeness crabs likewise need these wetlands for food, shelter, and breeding grounds.

For many animals and plants, such as wood ducks, muskrat, cattails, and swamp rose, inland wetlands are the only places they can live. Beaver may actually create their own wetlands. For others, such as striped bass, peregrine falcon, otter, black bear, raccoon, and deer, wetlands provide important food, water, or shelter. Many of the U.S. breeding bird populations—including ducks, geese, woodpeckers, hawks, wading birds, and many song-birds—feed, nest, and raise their young in wetlands. Migratory waterfowl use coastal and inland wetlands as resting, feeding, breeding, or nesting grounds for at least part of the year. Indeed, an international agreement to protect wetlands of international importance was developed because some species of migratory birds are completely dependent on certain wetlands and would become extinct if those wetlands were destroyed.

Natural Products for Our Economy
We use a wealth of natural products from wetlands, including fish and shellfish, blueberries, cranberries, timber, and wild rice, as well as medicines that are derived from wetland soils and plants. Many of the nation's fishing and shellfishing industries harvest wetland-dependent species; the catch is valued at US$15 billion a year. In the Southeast, for example, nearly all the commercial catch and over half of the recreational harvest are fish and shellfish that depend on the  estuary -coastal wetland system. Louisiana's coastal marshes produce an annual commercial fish and shellfish harvest that amounted to 1.2 billion pounds worth US$244 million in 1991. Wetlands are habitats for fur-bearers like muskrat, beaver, and mink as well as reptiles such as alligators. The nation's harvest of muskrat pelts alone is worth over US$70 million annually.

Recreation and Aesthetics
Wetlands have recreational, historical, scientific, and cultural values. More than half of all U.S. adults (98 million) hunt, fish, birdwatch or photograph wildlife. They spend a total of US$59.5 billion annually. Painters and writers continue to capture the beauty of wetlands on canvas and paper, or through cameras, and video and sound recorders. Others appreciate these wonderlands through hiking, boating, and other recreational activities. Almost everyone likes being on or near the water; part of the enjoyment is the varied, fascinating lifeforms.

Human impacts on wetlands
 Human activities cause wetland degradation and loss by changing water quality, quantity, and flow rates; increasing pollutant inputs; and changing species composition as a result of disturbance and the introduction of nonnative species.

Hydrologic Alterations
A wetland’s characteristics evolve when hydrologic conditions cause the water table to saturate or inundate the soil  for a certain amount of time each year. Any change in hydrology can significantly alter the soil chemistry and plant and animal communities. Common hydrologic alterations in wetland areas include:
·         Deposition of fill material for development;
·         Drainage for development, farming, and mosquito control;
·         Dredging and stream channelization for navigation, development, and flood control;
·         Diking and damming to form ponds and lakes;
·         Diversion of flow to or from wetlands; and

·         Addition of impervious surfaces in the  watershed, thereby increasing water and pollutant runoff  into wetlands.

Pollution Inputs
Although wetlands are capable of absorbing pollutants from the surface water, there is a limit to their capacity to do so. The primary pollutants causing wetland degradation are sediment, fertilizer, human sewage, animal waste, road salts, pesticides, heavy metals, and  Selenium. Pollutants can originate from many sources, including:

·         Runoff from urban, agricultural, silvicultural, and mining areas;
·         Air Pollution from cars, factories, and Power Plants, Old landfills and dumps that leak toxic substances; and
·         Marinas, where boats increase turbidity and release pollutants.

Vegetation Damage
Wetland plants are susceptible to degradation if subjected to hydrological changes and pollution inputs. Other activities that can impair wetland vegetation include:

·         Grazing by domestic animals;
·         Introduction of nonnative plants that compete with natives; and
·         Removal of vegetation for peat mining  
·          Harold Ornes is Dean of the College of Science at Southern Utah University (SUU) in Cedar City, Utah (since 1999)

Key Words : wetland, biodiversity, vegetation,Grazing, pat colony.

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