The world’s largest mangrove forest, the Sundarbans, is increasingly becoming vulnerable to rising sea levels and frequent natural disasters.

The Sundarbans form an archipelago straddling India and Bangladesh, and are part of the delta of Ganga, Brahmaputra and Meghna basin. The Indian part of the delta comprises of 102 islands (of which only 54 are inhabited) in 19 blocks in West Bengal.

About a million people in the Sundarbans coexist with 26 species of true mangroves, 234 species of birds and 47 species of mammals including the Royal Bengal tiger (uniquely inhabiting a mangrove forest) all of which face a threat from global warming.

Researchers of the School of Oceanographic Studies, Jadavpur University, estimate that annual sea level rise is from 3.14 millimetres recorded till 2000 to about 8 mm in 2010.

Professor Sugato Hazra, director, School of Oceanographic Studies said that 50,000 people were left homeless in the wake of cyclone Aila in May 2009, but there are no figures on how many of these climate change refugees returned.

“Indian Sundarbans Delta: A Vision” a report prepared by the institute as well as World Wide Fund For Nature - India (WWF) estimates that nearly one million people will become climate change refugees by the year 2050. The report suggests a planned retreat from vulnerable areas and planting of mangroves in those areas.

Anurag Danda, the WWF’s head of Sundarbans Landscape said that there is evidence that building embankments along the vulnerable islands will prove futile. Over the past decades some islands, both inhabited and uninhabited, have disappeared. While an inhabited island, Lohachara, was lost to the sea in 1990, by 2000, the uninhabited New Moore island was submerged. One estimate by the United Nations Development Programme in 2010 says that 15 per cent of the Sundarbans will go under by 2020.

Professor Hazra said a persistent threat lies over all islands. Severe erosion has reduced the land mass of Ghoramara island where 400 families reside.

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