Status of Indian Wetlands With Special Reference to Pesticides and Their Impact

Introduction

Wetlands are the precious life-sustaining water resources in India. Besides playing a vital role in the hydrological cycle, wetlands are the most productive ecosystems of the world and a potential source of carbon sequestration, although they covers about 4% of the earth’s ice-free land surface (Prigent et al., 2001). Ramsar Convention on Wetlands, which is an international treaty signed in 1971 for national action and international cooperation for the conservation and wise use of wetlands and their resources, defines wetlands as “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres”.

Globally, the areal extent of wetland ecosystems ranges from 917 million hectares (Lehner and Doll, 2004) to more than 1275 m ha (Finlayson and Spiers, 1999). One of the first widely used wetland classifications systems (devised by Cowardin et al., 1979) categorized wetlands into marine (coastal wetlands), estuarine (including deltas, tidal marshes, and mangrove swamps), lacustarine (lakes), riverine (along rivers and streams), and palustarine (‘marshy’– marshes, swamps and bogs) based on their hydrological, ecological and geological characteristics.

The Ramsar Classification is exhaustive, given under three broad groups as Marine/Coastal wetlands, Inland wetlands and Human-made wetlands. There are twelve categories under Marine/Coastal wetlands, twenty categories under Inland wetlands and ten categories under Human-made wetlands, as given below:

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  Marine/Coastal wetlands

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  Inland wetlands

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  Human-made wetlands

Wetlands are ecologically sensitive and adaptive systems (Turner et al., 2000). Wetlands exhibit enormous diversity according to their genesis, geographical location, water regime and chemistry, dominant species, and soil and sediment characteristics (Space Applications Centre, 2011). However, many wetlands which perform potentially valuable functions are continued to be ignored in the policy process. As a result many freshwater wetland ecosystems are threatened and many are already degraded and lost due to urbanization, population growth, and increased economic activities (Central Pollution Control Board, 2008) (Figure 1). Wetlands being dynamic and influenced by both natural and man-made activities, need frequent monitoring. Regular updation of the status of the wetlands is all the more significant in view of the accelerating pressure on the very existence of these resources due to developmental activities and population pressure being witnessed currently.

Figure 1.

Wetlands under threat

Status Of Wetlands In India

India with its annual rainfall of over 1,300 mm, varying topography and climatic regimes, supports diverse and unique wetland habitats (Prasad et al., 2002). The available estimates about the area extent of wetlands in India vary widely from a lowest of 1% to a highest of 5% of geographical area (Space Applications Centre, 2011).

Natural wetlands in India consist of the high-altitude Himalayan lakes, followed by wetlands situated in the flood plains of the major river systems, saline and temporary wetlands of the arid and semi-arid regions, coastal wetlands such as lagoons, backwaters and estuaries, mangrove swamps, coral reefs and marine wetlands. With the exception of bogs, fens and typical salt marshes, Indian wetlands cover the whole range of wetland ecosystem types elsewhere. In addition to the various types of natural wetlands found, a large number of man-made wetlands also contribute in sustaining the faunal and floral diversity.