Predicting possible landcover changes in the coral islands of Gulf Mannar due to climate change induced sea-level rise- a remote sensing based study

Corals are among the most diverse and beautiful natural system in the world. They are also the source of many flourishing species of flora and fauna. In the present scenario, coral reefs in Gulf of Mannar can be categorized as “degrading”. The causes for the rapid degradation presently witnessed include the anthropogenic activity and natural causes such as sea-level rise and climate change. Comparing the previous data with the present data is the only way to analyze the ecosystem and assess the changes caused by nature and human influence. The purpose of this study is to use satellite remote sensing as a tool to monitor and estimate the prominent changes that have taken place in the coral islands of Gulf of Mannar over the past three decades. Satellite images of 6 islands namely Van, Koswari, Vilangushuli, Anaipar, Vaalimunai, and Talalari acquired between 1979 and 2009 were chosen to assess the various changes in the ecosystem. Landcover maps were generated by interpreting the multi-date images and digitizing, using GIS software, according to common interpretation key. SRTM DEM of the area is used to model the possible effect of future sea-level rise as a result of climate change. The possible effects are seen as submergence of the beaches, marsh land, sea grass, dunes and other types of coastal and island vegetation. Though the limitations of SRTM DEM are realized, this study has been attempted since it is only at the reconnaissance level. The image processing approaches adopted for visual interpretation and prediction of loss of land due to sea-level rise are linear contrast stretching, Gaussian stretching, density slicing etc. Analysis of the above mentioned data warns us of the need to manage an ecosystem of high biological diversity from threats including climate change induced sea level rise.