The natural ecosystem of the Sundarbans mangrove wetlands is under threat due to human activities, including the dumping of industrial and domestic waste, as well as burnt oil from engine boats, launches, and ships.
The Sundarbans, the world’s largest mangrove forest, covers an area of about 10,000 square kilometres, which includes a section in India (West Bengal). Experts have indicated that the ecosystem has become vulnerable to pollution from oil spills, heavy metals, and agrochemicals, which may have altered the biogeochemistry of the mangrove ecosystem.
The Bangladesh portion of the Sundarbans spans 6,017 square kilometres and is located south of the Khulna, Bagerhat, and Satkhira districts along the Bay of Bengal. Of this total area, 4,143 square kilometres of land, including 1,874 square kilometres of water. The forest serves as a sanctuary for 425 species of trees, herbs, and creepers, as well as 246 species of wild animals, including the spotted deer, estuarine crocodile, and the famous Royal Bengal Tiger.
The mangrove ecosystem of the Sundarbans plays a crucial role in climate change mitigation by acting as a net sink (absorber) for climate-warming greenhouse gases. However, the mangrove ecosystem of Bangladesh, recognised as a highly diverse and productive area, faces increasing pressures from urbanisation and industrialisation. The factors affecting these mangroves include oil spills, heavy metals, agrochemicals (such as pesticides, herbicides, fungicides, and fertilisers), and nutrient pollution from domestic sewage and industrial effluents.
Human disturbances affect the flow patterns in the various channels and introduce pollutants into the mangrove ecosystem. Moreover, human activities lead to the overexploitation of natural resources.
Sources indicate that untreated water and effluents from different frozen food industries and sewage from Khulna city are routinely dumped into the Bhairab River. Additionally, waste from hospitals, clinics, poultry farms, kitchens, fish markets, and riverside residences also ends up in the river, which flows into the Bay of Bengal through the Sundarbans.
If an effective waste management system is not implemented, the regeneration processes of both forest and wildlife resources will be severely impacted, jeopardising the ecosystem of the forest.
Significant quantities of solid and liquid waste are discharged into the rivers daily from the coastal districts of Khulna, Satkhira, and Bagerhat, as well as from the Mongla and Payra seaports. This waste accumulates in the forestland, driven by the tidal flows of the rivers. Water transport and various small to medium-sized industries discharge toxic liquid and solid waste into the river daily, causing severe pollution and endangering aquatic life and biodiversity in the region.
Moreover, used petroleum products such as petrol, diesel, and oil are released from trawlers, motorised boats, barges, oil tankers, and ships, both domestic and foreign, at the Mongla and Payra ports, significantly affecting the forest’s ecosystem.
Fish traders report that solid wastes, including plastic bottles and cans, are often found floating in the rivers and canals that flow through the Sundarbans.
Tranquillity is essential for the natural growth and reproduction of vegetation and terrestrial animals in forests. Sanjoy Saha, Senior Scientific Officer at the Institute for Integrated Studies on the Sundarbans and Coastal Ecosystem (IISSCE) of Khulna University, stated, “The dumping of waste increases toxin levels in the water, which severely obstructs the growth and reproduction of aquatic creatures.”
Professor Dr Rezaul Haque from the Chemistry Department of Khulna University noted that burnt fuel is also detected inside the forest, posing a risk to the ecosystem of the Sundarbans. Dr. Haque conducted research to identify harmful elements in the soil, water, and aquatic animals in the region. His findings revealed the presence of various harmful substances in the soil, river water, and bodies of some aquatic species.
“I even found nickel—a substance typically found in waste from dry cell battery factories—in the bodies of oysters and hilsa fish,” Dr Rezaul added.
Mihir Kumar Doe, Conservator of Forests (CF) for the Khulna circle, noted, “Sundarbans vegetation is responding by changing productivity, canopy closure, tree coverage, and species diversity, or by migrating. Pollution diminishes the potential for natural regeneration by reducing seed viability, seedling germination, and seedling recruitment.”
Doe also stated, “The tree mortality rate is accelerating due to increased pollution. Additionally, the production of new leaves, leaf longevity, leaf area, net photosynthesis rate, stomatal conductance, and transpiration rate of leaves are all being adversely affected. Pollution is a significant factor in the growth and distribution of the mangrove forest.”
