Areal extent analysis of Ramsar sites in India
The wealth of the wetland ecosystem in India is enormously enriched with diverse flora and fauna. The wetlands of India play an important role in providing ecological services and goods to a greater extent of the society. Rapid urbanisation, industrialization and agricultural extension have been leading to the decrease in the areal extent of the wetlands. But from the last few years, management and conservation of the wetlands have got the highest attention in the national water sector (Bassi et al. 2014). According to the Ramsar Convention water bodies such as the rivers, lakes, coastal lagoons, mangroves, peat land, coral reefs are considered natural and water bodies such as the ponds, farm ponds, irrigated fields, sacred groves, salt pans, reservoirs, gravel pits, sewage farms and canals are considered manmade are included wetland ecosystem of India. The following figures (Figs. 1, 2) show the potential of wetland in India and their areal extent. Sundarban has the highest wetland area of 423,000 hectares (ha), which is also one of the world heritage sites designated by UNESCO providing livelihood to thousands of villagers. Following Sundarban, the top 4 wetlands of India in terms of areal extent are Vembanad-Kol Wetland (151,250 ha), Chilka wetland (116,500 ha), Kolleru lake (90,100 ha) and Bhitarkanika Mangrove (65,000 ha).
Wetlands of India has been designated as the Ramsar site in different time of the year since the nineteenth Century. The number of wetlands designated as the Ramsar site at different time has been shown with help of the cartographic representation (Fig. 1) (Ramsar 2020, https://rsis.ramsar.org/). From the list of 37 wetland designation years of each has been classified into the four-time period that is 1981–1991 (6), 1992–2000 (0), 2001–2011 (19) and 2012–2020 (12). From Fig. 1, it can be seen that the highest time (49%) of designation is from 2001 to 2011 which signifies the period when more attention towards conservation and sustainable development of the wetland has been looked upon. This period also witnessed the beginning of the water crisis both surface and groundwater throughout the world. Of the 37 wetland areas classification (ha) has also been and has been divided into 4 classes that is < 1000 (14), 1001–25,000 (16), 250,001–50,000 (3) and > 50,000 (5) (Fig. 2). The highest number of the wetland is found under the areal extent of 1001–25,000 ha. In recent years areal extent of wetlands is decreasing because of the climate change with greater intensity of drought, which leads to drying of surface water bodies (https://www.ramsar.org/).
Present situation of wetlands in India
Hindukush and Himalayan mountain ranges play an important role in the spatial and temporal inconsistency in precipitation and temperature aspects of the tropical and sub-tropical regions of Asia including India. Most of the rivers of India is fed the melting glaciers and the deposition of huge sediment can be seen at the mouth of the rivers. This climatic variability and the geomorphic diversity have led to the enrichment of the wetlands in India. Based on the climatological aspects and drought intensity in India, it can be concluded that the eastern and central part of India (West Bengal, Madhya Pradesh, Konkan, Bihar and Orissa), the frequency of drought is one in five years. Whereas, drought occurs once every four years in the parts of southern Karnataka, eastern Uttar Pradesh and Vidarbha region (Nath et al. 2017) (Fig. 3). In the area where the intensity of the drought is higher, chances of the drying up of the wetlands are common (Fig. 4). Figure 3 signifies the intensity of drought is higher in the south, central and eastern parts of India. Wetlands located in those zones are the most vulnerable. The areas where the drought intensity is high will lead to the drying of both the surface and groundwater zone. Low precipitation will also lead to a decrease in the groundwater recharge over the region. The low precipitation together with the drying of the surface water bodies leading to the exploitation of groundwater. This led to alteration of the hydrological regime of wetlands which are associated with the aquifers and has made significant deterioration of their ecological characteristics (Froend et al. 2016). From both Figs. 3 and 4, it can be witnessed the Kolleru wetland is located within the drought-prone zone thereby requiring sustainable management otherwise it will lead to the degradation of the ecological and societal character of the wetland.