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COVER STORY

     Wetlands - Nature's Neglected Lot: do we need them?
Rajinikanth R and T.V. Ramachandra

Wetlands are fragile ecosystems, vulnerable even to small changes in the composition of their biotic and abiotic factors. In recent years, there has been increasing concern over the continuing degradation of the world's wetlands, particularly, rivers and lakes. Wetland sustains all life forms and performs some useful functions in the maintenance of overall balance of nature. Representing the interface between land and water systems, they are among the most productive and biologically rich ecosystems on earth and also the most endangered.                           

"Wetlands" is the collective term for marshes, swamps, bogs, and similar areas. They have been described as the "kidneys" of the landscape as they filter sediments and nutrients from surface water, and "biological supermarkets" as they support all life forms through extensive food webs and biodiversity. They are dynamic ecosystems, continually undergoing natural changes like infilling with sediments and nutrients, subsidence, sea level rise, etc., and the direct and indirect human activities, have also considerably altered the rate of change of wetlands.

Humans depend on water, plants and animals for their survival. Many people in India depend on the biological wealth found in their immediate environment for food, fodder and fuel. The diverse biological resource is a true renewable resource, which is being threatened today. Due to lack of proper management, most of the world's biological resources are being lost which cannot be regenerated. With advancement in science, these bio-resources rich in diversity have tremendous potential in the pharmaceutical, food and other industries. 

Wetlands are of two basic types: Inland (also known as non-tidal, freshwater wetlands) and coastal (tidal, salt water or estuarine wetlands). In addition to these, artificial or man-made wetlands have also been included under wetland classes. Inland wetlands receive water from precipitation, snowmelt, ground water, and runoff. Coastal and estuarine wetlands receive water from precipitation, surface water, tides and ground water discharge.

ARE WETLANDS IMPORTANT FOR OUR FUTURE? 

Wetlands are amongst the earth's most productive ecosystems, which directly or indirectly support millions of people and provide goods and services to them. Their important functions include the movement of water through the wetland into streams or oceans; decay of organic matter; release of nitrogen, sulphur and carbon into the atmosphere; removal of nutrients, sediment and organic matter from water moving into the wetland; and growth and development of all organisms that require wetlands for life. Their direct benefits are as components/products such as fish, timber, recreation, water supply, etc. The indirect benefits arise from the functions occurring within the ecosystem such as flood control, ground water recharge, shoreline stabilization and storm protection, and sediment and nutrient retention. Apart from these, their mere existence may be of great significance to some people, being a part of their cultural heritage.

One of the important benefits provided by wetlands in improving water quality is by filtering sediments and nutrients from surface water. Wetlands act as natural purification mechanisms, enhancing the water quality in the vicinity. Swamps and marshes are particularly good at filtering sediments and nutrients, which are the major cause for wetland degradation. Wetland vegetation plays a major role in removing 90% of dissolved nutrients such as nitrogen and phosphorus and to some extent heavy metals. In addition to functioning as a purification mechanism, they also play a valuable role in reducing turbidity of floodwaters (as runoff and surface waters pass through wetlands, pollutants are removed or transformed through physical, chemical and biological processes).

Apart from these, the socio-economic values provided by wetlands through water supply, fisheries, fuel wood, medicinal plants, livestock grazing, agriculture, energy resource, wildlife resource, transport, recreation, tourism, etc., are significant. The functional properties of wetland ecosystem demonstrate clearly its role in maintaining the ecological balance. 

WHY ARE WETLANDS BEING DEGRADED AND LOST?

Wetlands are dynamic eco-systems that are in continual change through ongoing processes of subsidence, flooding, erosion, drought, sea level rise, infilling with sediment or organic material. Many wetlands are temporary features of the landscape and will change and eventually disappear.

Wetlands are estimated to occupy around 8.6 million km2 (6.4 %) of the earth's surface. Out of these, about 4.8 million km2 are found in the tropics and sub-tropics. The wetland area of the world has reduced by 50% compared to what existed in 1900. The major activities responsible for the wetland loss can be attributed to urbanization, drainage for agriculture and water system regulation (IUCN, 1999). Development activities like excavation, filling, draining, etc., are the major destructive methods, which have resulted in a significant loss of wetland acreage throughout India.

The impacts on wetland may be grouped into five main categories: loss of wetland area, changes to water regime and water quality, overexploitation of wetland products and introduction of exotic or alien species. 

Wetlands are under increasing stress due to urbanization, technology development, economic growth and various other anthropogenic activities, which have accounted for their over exploitation and degradation. They are threatened by excessive loading of silt and nutrients from various sources (point and non-point sources) due to the removal of vegetation cover in the catchment area. Vast areas of wetlands have been encroached for various purposes such as agriculture, settlements, etc., leading to shrinkage of wetland area. Weed infestation and colonization by water hyacinth causes further degradation of much of the wetland ecosystem.

Wetland waters are diverted for farming, public water supply, hydroelectricity and navigation, which can change its water regime.

Effluents from industries, uncontrolled use of fertilizers in the surrounding agricultural lands, discharge of domestic wastes and sewerage from human settlements contribute to the water quality deterioration of these systems.

Such decrease in the quality and quantity has contributed to decline in the diversity of flora and fauna, migratory birds and also the productivity of the system. Several thousand species have now become extinct and many other sustainable species, products like fish, timber, medicinal plants, water transport and water supply are over exploited.

Major threats faced by wetlands are hunting and associated disturbances; encroachment; human settlements; reclamation for urban and industrial development; pollution from industries, domestic and agricultural areas; fishing and associated disturbances; commercial logging and forestry; removal of vegetative layer in the catchment and consequent soil erosion; weed infestation; conversion to aquaculture ponds; diversion of water for farming; water supply; hydroelectricity generation, etc. It has been estimated that nearly 1 hectare of the world's wetland area is getting degraded every minute. 

HOW TO RESTORE DEGRADED WETLANDS?

Restoration is required to improve the quality of water and its catchment conditions in order to ensure sustainable use of wetland resources. The necessary steps to be implemented in restoring lakes for their long-term sustenance include:

·Pollution impediment: Wastewater, and solid and semi-solid wastes entering the lake from external sources must be stopped before any restoration work is implemented.

·Harvesting of macrophytes: Water hyacinth and other nuisance vegetation present in the lake, the cause for eutrophication, must be removed manually or mechanically. Weed infestation can also be controlled chemically with methyl-chlora-phenoxy-acetic acid, hexazinore, diuron, and high speed diesel oil, etc., and biologically controlled by introducing Pila globosa (tropical snail), Chinese grass carp (fast growing fish) and Manatee (sea-cow) that feed on many aquatic plants.

·Draining of water: The water present in the lake must be cleaned or drained completely.

·Desiltation: Dredging of the sediments in the lake to improve soil permeability, water holding capacity and ground water recharge.

·Intervention in the lake ecosystem: It is desirable to oxygenate the entire lake (from top to bottom) in order to reduce the oxygen depletion that occurs in the hypolimnion due to decomposition of organic matter and kill sulfur-reducing anaerobes. 

·Reduction in the external loading: A reduction of the external loading can be carried out either by elimination of the total wastewater input to the lake or by use of wastewater treatment methods like screening, grit chamber, chemical precipitation, activated sludge process, etc.

Restoration with an ecosystem viewpoint helps in correcting point and non-point sources of pollution. This along with regulations and planning for wildlife habitat and fishes helps in arresting the declining water quality and the rate of wetland loss. These restoration goals require profound planning, legislation, funding and active involvement from all levels of organization [Governmental and Non-Governmental Organizations (NGOs), research organizations, media, etc.] through interagency and intergovernmental processes, made favorable by allowing them to innovate and undertake restoration programs. A network of educational institutions, researchers, NGO's and the local people is suggested to help restore the fast perishing wetland ecosystem and conserve those at the verge of death by formulating viable plans, policies and management strategies. 

A century of neglect has already resulted in the loss of 50 % of these precious ecosystems. The present and future generations have that much less resources to share among themselves. We need to restore, conserve and manage this neglected lot of NATURE. To neglect further will only hasten the destruction of all wetlands of the earth, and ultimately humankind's doom.