INTRODUCTION
Two third of this world is surrounded by waterbodies. Wetlands occupy an estimated amount of 6.4% of the earth's surface(IUCN Environmental Policy and Law paper No.38). Wetlands are among the earth's most diverse and productive ecosystems. Wetland sustains all life and performs some useful functions in the maintenance of overall balance of nature. As a result of rapid urbanization, increase in population, technical development, economic growth and various anthropogenic activities, more and more waste materials were discharged into the natural sources of water bodies apart from conversion of wetlands for anthropogenic activities. Due to this, declination of wetland quality and quantity takes place and the requirements for water have also increased along with greater demands for higher quality water. Hence it is imperative to conserve and preserve these wetlands to make it fit for local consumption and to maintain the ecological balance.
Definition
'Wetland' denotes any area covered with water, which includes all rivers, lakes, paddy fields and periodically flooded lands. As per the definition given at Ramsar Convention (Ramsar, 1996), 'Wetlands are 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 salty, including areas of marine water the depth of which at low tide does not exceed 6m'.
Importance of Wetlands: Funtions and Values
Wetlands are amongst the Earth's most productive ecosystems. Wetland systems directly or indirectly support millions of people and provide goods and services to them. The growth and development of all the organisms that require wetlands for life. Wetlands may benefit directly as components / products such as fish, timber, wild life, fertile land for agriculture, water transport, recreation and water supply or indirect benefits which arise from the functions occurring with in the ecosystem such as flood control, ground water recharge, storm protection, shore line stabilization, water quality improvement, sediment and nutrient retention. The mere existence of wetlands may be of a great significance to some people because it is a part of their cultural heritage. Apart from these, some socio-economic values through water supply, fisheries, fuel wood, medicinal plants, livestock grazing, agriculture, energy resource, wildlife resource, transport, recreation and tourism etc., is significant,and in maintaining the ecological balance of the ecosystem.
Wetland Loss and Degradation
Wetland constitutes important features of the landscape and subjected to constant change due to urbanisation and in some cases has led to disappearance. The impact on wetlands may be grouped in to five main categories: loss of wetland area, changes in water quality, changes to water regime, overexploitation of wetland products and introductions of endangered or alien species.
Wetlands are facing problems due to major proportion of the population in the catchment area, urbanization and industrialization; and various human activities, which has accounted for the over exploitation and leads to degradation of wetlands.
Wetlands are threatened by excessive loading of silt and nutrients from various sources(point and non-point sources)due to removal of vegetation cover in the cacthment area. Vast areas of wetlands have been encroached for various purposes such as for agricultural purposes, for settlements etc., due to rapid urbanization. These threats are resulted in shrinkage of area. Weed infestation and colonization by water hyacinth causes further degradation of most of the wetland ecosystem.
Effluent from industries, uncontrolled use of fertilizers in the agricultural lands, discharge of domestic wastes and sewerage from human settlements, all contribute to the water quality deterioration to these systems. Wetland waters are diverted for farming, public water supply, hydroelectricity and navigation, which can change its water regime.
Apart from these quality and quantity declinations,it has also decreased the Biological diversity of flora and fauna, migratory birds and also the productivity of the system. Simultaneously several thousand species are now endangered and many other sustainable species, products like fish, timber, medicinal plants, water transport and water supply are over exploited.
Status of Wetlands in Bangalore
Bangalore has many man-made wetlands, that were artificially built for various hydrological purposes and mainly to serve the needs of irrigated agriculture. The number of man made lakes has fallen from 262 in 1960, to some 81 lakes at present (Lakshman Rao, N. et al 1986). The quality of water has reduced due to discharge of industrial effluent and domestic sewage ( Shivshanker, T.V. et al, 1985). Many lakes have been lost by converting wetlands for residential, agricultural and industrial purposes ( Venkataraman R.,1997). More than 28 % of lakes suffered from various degree of eutrophication and nearly 30% of vegetables were grown in untreated water(Krishna, M.B. et.al).Earlier investigations also revealed that,for nearly 40% of the lakes, sewage was the main source, 13% lakes surrounded by slums and loss of catchment for nearly 35% lakes surveyed between 1973 and 1996 (Deepa,R.S, et.al,1996).Now it has become necessary to preserve and conserve these vanishing ecosystems, which is important for various purposes and to achieve ecological sustainability.
