Spatio-temporal analysis of mangrove loss in vulnerable islands of Sundarban World Heritage Site, India

Abstract

Mangroves are unique ecosystem found mainly in tropical coastal region in saline environment and under tidal influence. It has enormous ecological and economic value to the environment and local people. However, the problems are arising in tropical coastal region like Sundarban, where both natural and ever increasing anthropogenic activities have complicated the growth and development of mangroves. Therefore, spatio-temporal monitoring of mangroves has huge importance for their conservation in Sundarban World Heritage Site, the largest mangrove population in the world. Remote sensing has been proven as an important tool to monitor such ecosystem, but the traditional pixel based approach has several drawbacks. Recently, Object-based Image Analysis (OBIA) approach in remote sensing has helped to overcome such drawbacks. The present study attempts to analyse the status of mangroves over the time period of 40 years (1975–2015) in the study area using Landsat time series images through OBIA. The result reveals that the mangroves are gradually reducing over the last 40 years and about 4% mangrove area has been converted into water. It is a major indication of increase in sea water level, making many islands vulnerable. The time series analysis in some islands, like Bhangaduni, Bulchery, Dalhousie and Halliday shows the land area as well as mangroves have been destroyed more than one-third. If the process continues at the same rate, these islands may soon completely disappear.