The Sundarbans — the world's largest mangrove forest and a UNESCO World Heritage site — faces a triple threat from industrial accidents, rising salinity, and climate-induced habitat loss. Using satellite imagery analysis, Bangladesh Forest Department data, and UNESCO monitoring reports, we document the accelerating degradation.
- ▸The Sundarbans, spanning 10,277 square kilometres across southwestern Bangladesh and India, is the largest contiguous mangrove forest on Earth.
- ▸It is home to the Bengal tiger, the Irrawaddy dolphin, and over 300 species of birds.
- ▸It also serves as the primary storm surge buffer for 35 million people living in the Ganges-Brahmaputra delta.
- ▸> UNESCO monitoring data from 2025 shows that the Sundarbans has lost 12.4% of its forest canopy cover since 2010 — an average loss of 82 square kilometres per year.
- ▸At current rates, critical ecological thresholds could be breached within 25 years.
The Sundarbans, spanning 10,277 square kilometres across southwestern Bangladesh and India, is the largest contiguous mangrove forest on Earth. It is home to the Bengal tiger, the Irrawaddy dolphin, and over 300 species of birds. It also serves as the primary storm surge buffer for 35 million people living in the Ganges-Brahmaputra delta. By multiple measures, it is in decline.
"UNESCO monitoring data from 2025 shows that the Sundarbans has lost 12.4% of its forest canopy cover since 2010 — an average loss of 82 square kilometres per year. At current rates, critical ecological thresholds could be breached within 25 years.
The Oil Spill Threat
On December 9, 2024, an oil tanker collision in the Shela River spilled an estimated 350,000 litres of furnace oil into the Sundarbans waterway network — the second major spill in the region in four years. A previous spill in December 2020 released 350,000 litres of heavy fuel oil into the same waterway system.
According to the Bangladesh Forest Department's impact assessment, the 2024 spill contaminated 48 kilometres of waterways and 12 square kilometres of mangrove vegetation. Despite a containment operation involving 600 personnel and 15 vessels, the department's follow-up survey in March 2025 found that 23% of affected mangrove stands showed crown dieback and reduced regeneration capacity.
Salinity Intrusion
The more insidious threat is salinity intrusion. Data from the Bangladesh Water Development Board (BWDB) shows that the salinity front in the Sundarbans has advanced inland by 8.7 kilometres since 2010. Soil salinity measured at 24 monitoring stations increased by an average of 34% between 2010 and 2025.
A 2025 study by the Bangladesh Forest Research Institute (BFRI) found that heritiera fomes (sundari), the dominant tree species that gives the forest its name, has experienced a 43% decline in basal area per hectare since 2000, with the highest mortality rates in high-salinity zones. The study projects that if current salinity trends continue, 68% of the current sundari habitat will be unsuitable by 2045.
Cyclone Buffer Degradation
The storm surge protection function of the Sundarbans is measurably declining. A joint study by the Institute of Water Modelling (IWM) and the University of Dhaka, published in 2024, found that a 1-kilometre reduction in mangrove width results in a 15-22% increase in storm surge height inland. With the forest's average width declining from 42 kilometres in 2000 to 36 kilometres in 2025, the surge protection provided to the 35 million people in the cyclone zone has diminished by approximately 18%.
Tiger Population
The Bengal tiger population in the Sundarbans was estimated at 114 individuals in the 2024 camera trap survey conducted by the Bangladesh Forest Department and WildTeam — up from 106 in 2020 but still critically below the estimated carrying capacity of 200-250. The primary threat is habitat shrinkage and prey base depletion, with the spotted deer population declining by 27% since 2015 due to habitat loss and poaching.
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