GIS-based Valuation of Ecosystem Services in the Lower Delta Plain of West Bengal with Special Reference to Indian Sundarbans

Abstract

The Indian Sundarbans partly hosts the world’s largest mangrove forest and support the livelihood of almost five million people. The Holocene delta of Indian Sundarbans was formed by the river Ganges. The decay of the distributaries of the river Ganges in deltaic West Bengal began with the eastward avulsion of the river Ganges. The rivers of Sundarbans now stand disconnected from their sources and therefore do not get a significant amount of freshwater from upstreams. The people of Sundarbans depend on the services of the Sundarbans ecosystem which is directly linked to the upstream freshwater flow, rainfall and groundwater. The scarcity of freshwater during dry seasons, high salinity of surface water and soil, siltation and drainage congestion are major constraints on livelihood security in this area. The biodiversity of Sundarbans is also threatened by water stress. To ensure the sustainable conservation of the rich biodiversity and well-being of the people of Sundarbans, improving ecosystem services in the region is extremely essential. From this perspective, the present study aims to identify major flow-dependent ecosystem services in the region and estimate the value of those ecosystem services using geoinformatics. The land use land cover (LULC) maps have been prepared for the years 1990, 2000, 2010 and 2020 from Landsat images for the valuation of major ecosystem services. Accuracy assessment has been performed using high-resolution satellite images and field data. Change detection analysis has been done to understand the changing land use pattern in the study area. The LULC-based valuation of the ecosystem services has been carried out for the years 1990, 2000, 2010 and 2020. The area under each LULC class has been multiplied by the global Ecosystem Service Value (ESV) of that class to calculate the total ESV of the specific LULC class. The study reveals that the ESVs are the highest for freshwater bodies including rivers, and estuaries followed by forests. With the decreasing upstream freshwater flow and deteriorating mangrove health, the services of flow-dependent ecosystems have changed drastically.