Human pressure remains the largest threat to the Sundarbans like any other mangroves across the world. Though Sundarbans is claimed to be pristine in state, more than 50% of the north-western parts and intertidal lands of Sundarbans delta have been continuously cleared for human habitation and settlement, agriculture and brackish water fisheries. Landuse change, pollution from industrialization and economic activities e.g. shipping port close to the forest, intensive aquaculture and over-extraction of resources remain the major threat to the forest.
Sundarabans lies in the Khulna administrative zone – a major industrial hub for the country, offering sound strategic location for shipping yards, paper mills and port. Unchecked pollution from these sources, intensification of economic activities and landuse change in recent years have further aggravated the decline of its ecosystems despite the fact that, Sundarbans is a proven natural coastal barrier saving the forest and inland. Surely as cyclones become more frequent with global warming, significance of such natural protection increases exponentially.
Dry season freshwater flow into the mangrove dominated western Sundarabns is reduced from the construction of Farakka barrage on the distributries of teh Ganges river since 1975. Freshwater starvation, of both natural and anthropogenic, led the major macrofauna (arboreal primates, gavial, large cats) of the system threatened. Even more alarmingly, it alter the natural salinity of the forest system allowing salinity intrusion. Major mangrove species of the Sundarbans is Heriteris fomes, more suited to lower salinity level. Salinity intrusion into the western Sundarbans in India already has eliminated this low salinity tolerant species from the zone. Assumably, a similar fate looms for the species in Bangladesh as well as freshwater flow gets increasingly squeezed due to the barrage.
Waste discharges from the trawlers, fishing boats and cargoes, unchecked sludge disposal from the industries add to already contaminated water in the rivers of the Sundarbans delta. A major oil-spill from a capsized cargo in Shela river in the Sundarbans in 2014, draw huge public attention. The disaster exposed zero-preparedness in disaster management. World alarmingly observed its slap on the biodiversity and its ecosystem as locals started oil-recovery under a health-hazardous condition. Little has improved since then. Neither the cargo-shipping through the rivers of the Sundarbans have ceased nor has the disaster management seen any improvement.
Furthermore the government in Bangladesh has undertaken a coal-based thermal power plant at Rampal, close to the Sundarbans. Despite the government assuring environmental impact assessment of the project, experts are doubtful and concerned about the future of the forest.
Nutrient enrichment is a major threat to marine ecosystems. Although mangroves have been proposed to protect the marine environment from land-derived nutrient pollution, nutrient enrichment can have negative consequences for mangrove forests and their capacity for retention of nutrients may be limited(Reef et al., 2010).
Non-point source pollution from agricultural fields and yet more alarmingly, the booming aquaculture industry in and around the Sundarbans enrich river water with nutrients. Consequence of such nutrient enrichment e.g. hypoxia , yet unobserved in the area, cannot be invalidated. In fact, Manna et al. (2010) already reported eutrophication and its possible consequences on the sea from in Indian part of Sundarbans.
Reef, R., Feller, I. C., & Lovelock, C. E. (2010). Nutrition of mangroves. Tree Physiology, 30(9), 1148-1160.