tamilnadu Wetland
Wetlands are increasingly being recognised for their vital role in nature and in natural processes that extend far beyond their geographical locations and boundaries. They are the highest producers of biomass compared to any other ecosystem type worldwide, far outstripping River estuaries, tropical rain forests and even coral reefs (Ricklefs and Miller 2000). India is the seventh largest country in the world, occupying only 2.4 % (i.e.3.28 million sq km) of the world's land area and supports over 16% of the world's population. The wetland ecosystems in India are spread over a wide range of varied climatic conditions, variously estimated to be occupying 1-5% of the geographic area supporting about a fifth of the known biodiversity. Like any other place in the world, there is a looming threat of unsustainable human pressures to the Indian wetlands. Looking into the urgent need for sustainable management of these assets, the Government of India has initiated many steps in terms of policies, programmes and plans for the preservation and conservation of these ecosystems.
The total wetland area estimated by the Space Applications Centre (SAC, ISRO), Ahmedabad is 15.26 M ha, which is 4.63% of the geographic area of the country. As per the 2011 National wetland atlas, Tamil Nadu has 6.92% of its land mass categorized under wetlands. These wetlands resources are mainly replenished by the seasonal rainfall during the northeast monsoon. The state is among the five Indian states that have over-exploited their ground water resource (Narayanamoorthy, 2010). According to Parvathi (2011), with a per capita water availability less than the national average, Tamil Nadu is one of the water starved states.
The Central government notified the Wetland (Conservation and Management) Rules, 2010, as a significant step to conserve, manage and to maintain the ecological character of the wetlands, without curtailing and restricting the legitimate and wise use of these ecosystems. The ammended Wetland Rules 2017 are in line with the ‘Wise Use’ philosophy of the Ramsar Convention, and they accord greater emphasis on maintaining ecological character and integrity of wetlands.
The Wetland Rules as specified in Rule 3 require the State Governments/UT administrations to prepare a wetland inventory within their jurisdiction and identify / prioritize wetlands for notification by the Central Government. Further, the State Governments/UT administrations are required to submit a brief document for each of the identified/prioritized wetlands.
The primary objective of the framework is to identify/prioritize wetlands for conservation. This will have to be supported by a brief document on each of the wetlands giving the information as specified in Rule 6 as follows.
For the present project funded by the State Planning Commission Tamil Nadu State Land Use research Board (SPC-TNSLURB), Sálim Ali Centre for Ornithology and Natural history (SACON) proposed that 100 wetlands would be prioritized for conservation after the preparation of the brief document for wetlands. To achieve the target we identified 141 wetlands. The wetlands were selected based on the SACON ATLAS (Prasad et al., 2004), Scientific Literature, internet based bird data and Google imagery. The SACON Atlas did not have wetlands prioritized for almost 16 districts, while our emphasis was to give a fair representation to all the 32 districts of Tamil Nadu. Moreover, the Wetland Rules 2017 ruled out the wetlands form Protected Areas (PAs) or under the jurisdiction of the forest department, hence the reason for selecting 141 wetlands in total.
During the present study we prepared the brief document for maximum number of wetlands form the Kanchipuram District (15 wetlands) while a minimum of two wetlands were documented for the Nilgiris district. We physically visited all the wetlands selected and observed that almost 34 wetlands were completely dry for a minimum of three years to 10 years. This was attributed to lack of rainfall and diversion of channel waters. The wetlands however showed hydric soil characteristics indicating their importance in the landscape. Among the wetlands with water, we recorded Eutrophic, Mesotrophic and Oligotrophic wetlands that supported over 444 species of plants representing 95 families. The flora comprised of 31 Alien Invasive species including five invasive aquatic species, 27 fresh water plants and six marine plants. The 401 types of fauna were represented by Insects – 50 species, 82 species of Butterflies, 34 species of Odonata, six species of spiders, 34 species of fish species, four species of Amphibians, seven species of reptiles, 170 species of birds (92 Terrestrial, 60 Wetland birds and 18 Wetland dependant birds) and 14 species of domestic and wild mammals. Moreover the common problems that we documented for most of the wetlands include Reduction in area (Shrinkage), Reduction in depth (Siltation), Encroachments (Local Residents/Builders/Government), Algal blooms, Aquatic weeds, Decline or Loss of Fisheries, Eutrophication, Organic Pollution and Toxic Pollution. Apart form these, we observed illegal hunting of wild birds in around 20 wetlands.
For helping in managing the wetlands we mapped the zone of influence for each of the wetlands by plotting the contour maps along with the landscape elements. We marked a fixed 2 km buffer around the wetlands using Arc map, the SRTM data was downloaded form USGS to generate the elevation and contours around the wetlands while the Land Use Land Cover data of 2004-2005 was used form Landsat 5 and Resourcesat satellites. Based on the findings and the landscape characteristics around the wetlands we have suggested some remedial measures which include lake water quality treatment, installation and management of sewage treatment plants, weed removal, shoreline protection and management of catchment areas to check erosion.
Moreover, based on our primary studies we have calculated the Wetland Health Status score for each of the 141 wetlands taking into consideration the Ecosystem services, Land use patterns, threats and biodiversity values recorded during our field visits. Simultandously we have ranked the wetlands based on the score and have found that out of the 141 wetlands 23 wetlands need immediate attention while four among the 23 are in a critical state. Thirty two wetlands are in a fairly healthy state, although we recommend that all the wetlands be wisely used and sustainable conservation management plans be implemented.