Detection of Coral Reefs Degradation using Geospatial Techniques around Saint Martin’s Island, Bay of Bengal

Saint Martin’s is a unique island located in the Bay of Bengal where coral species are abundant due to its favorable and unique environmental conditions. Coral communities are in great danger due to global climate change, direct commercial coral extraction and unplanned tourism around the island. The present study attempts to identify the coral zone and mapping of coral reefs from the period of 1980 to 2018. The study utilized five sets of multi-temporal Landsat satellite images to examine the changes of coral reefs in Saint Martin’s Island during the study timeframe. Geospatial and image processing software was used for spatial coral colony mapping and data analysis. Satellite images processed to remove water depth impacts and supervised classification technique using the maximum likelihood decision rule suggested the spatial change of coral colonies over time. The result of the study indicates that coral colonies decreased steadily throughout the study period. A total area of 0.9342 km2 of coral colonies disappeared during the study period from 1980 to 2018. Field observations around Saint Martin’s Island indicates that destruction of coral reef habitat was basically caused by anthropogenic activities like tourism and extraction of coral by fisherman. Analysis of the historical data regarding tourism, population and households, and Sea Surface Temperature (SST) along with field observations of these parameter during 2018, suggests that anthropogenic factors are more significant than natural factors for causing coral reef degradation. It is very crucial to raise consciousness not only in the vicinity of Saint Martin’s Island but more widely regarding the significance of the biodiversity of the Island.