Study Finds 15% of Sundarbans Losing Climate Resilience Over 25 Years

A study published in Communications Earth and Environment finds that 10 to 15 per cent of the Sundarbans UNESCO World Heritage mangrove forest, equivalent to 610 to 990 square kilometres, has experienced a measurable loss of ecological resilience between 2000 and 2024. The decline, driven by cyclone damage, climate change, and human pressure, manifests as critical slowing down, where ecosystems take progressively longer to recover from disturbances.

The most severely affected zones lie in the central and south-eastern Sundarbans, particularly seaward areas from the Satkhira to Sharankhola ranges in Bangladesh and India's western mangrove stands near northern boundaries. Following cyclones Sidr, Rashmi, and Aila between 2007 and 2009, areas covering 820, 732, and 1,138 square kilometres respectively shifted from resilient to moderately resilient categories. A new hotspot of resilience loss has also been identified in the north-eastern region, where long-term analysis shows steep declines along coastal boundaries. The Sundarbans spans over 10,000 square kilometres across India and Bangladesh.

Rising temperatures reduce resilience by affecting species richness and canopy characteristics, while erratic rainfall patterns undermine the hydrological balance that sustains mangroves. The dominant Sundari tree (Heritiera fomes) has been affected by a top-dying disease since the 1960s, converting portions of the forest from a carbon sink to a carbon source. Reduced freshwater flow from upstream dams increases porewater salinity, forcing plants to expend energy on osmoregulation rather than growth. Encroachment, shrimp farming, and illegal logging of large canopy trees are further degrading structural complexity and recovery capacity.

Researchers estimate an annual loss of approximately $16.72 million in timber value from the Sundari disease alone. The study links Sundarbans trends to broader resilience loss in other tropical forests including the Amazon. Recommended interventions include protecting mature trees from poachers through strengthened patrolling, involving local communities in awareness and monitoring programmes, and incorporating climate impact assessments into forest management policy. For India, effective management of the western Sundarbans requires cross-border coordination with Bangladesh and integration with Namami Gange river rejuvenation priorities.

Key figure — $16.72 million annual timber value loss from Sundari tree disease