Sundarban mangroves: Impact of water management in the Ganga River Basin

Abstract

Sundarban, the single largest contiguous area of mangroves in the delta of Ganga, Brahmaputra and Meghna, is shared between India and Bangladesh. The landscape consists of a network of tidal creeks, waterways, marshes and pools, low and high mangroves, strands of grasses and islands which disappear and reappear twice a day with the tides. Like other mangroves, the Sundarban has enormous ecological value as it stabilizes the coastline and protects against cyclonic storms, hosts very rich biodiversity, supplies forest products, hosts and supports coastal and near-shore fisheries, sequesters carbon disproportionate to its areal extent and serves the ecotourism. Sundarban is the only mangrove habitat of tigers, an endangered species. Sundarban was declared as a reserve forest by the British in the mid 1800s for the sake of resource exploitation. However, after independence, India established three wildlife sanctuaries that were later merged into a national park. In late 1970s, Bangladesh also set up wildlife sanctuaries in its part of Sundarban. The entire Indian part of Sundarban has now been designated as a biosphere reserve whereas some parts in both India and Bangladesh were also inscribed on the World Heritage list in 1987 and 1997 respectively. Despite the conservation status, the Sundarban mangroves are increasingly impacted by various land use and water management practices throughout the GBM basin through a complex interaction between hydrology, salinity and sediments. Hydrological alterations caused by the Farakka barrage affect the salinity gradients, transport of sediments, nutrients and pollutants, and accretion-erosion dynamics. Consequently, these changes impact the biodiversity, productivity, agriculture and people and their livelihoods. The projected climate change-induced sea level rise is another major threat looming large over the Sundarban. While our understanding of the functioning of the Sundarban mangrove ecosystems remains poor and influenced by terrestrial approaches, their future depends upon the management of land and water resources throughout the Ganga-Brahmaputra basin, that in turn requires an integrated river-basin-wide appropriate strategy backed by political will.