Due to global warming and consequent sea level rise all human-inhabited islands in Sunderbans, the largest deltaic region in the world, face the threat of getting submerged if the dykes are breached during high tide.

"The dykes were constructed a century ago to settle people and prevent islands from getting submerged. Now the waters rise above the dykes and innundate islands during high tide, which happens twice a day," Badal Mallick, aged 65, an island dweller says.

In August, September and November, the swelling rivers fed by monsoon rain, strong winds and rising sea level led to water overflowing the dykes of 54 human-inhabited islands of Sunderbans flooding. The floods caused damage to the standing paddy crops, releasing fish from the ponds, flattening mud houses, killing livestock and making the farmland saline by sea water.

Ocean scientists say rising sea level caused by global warming has already submerged Lohachara island and Suparibhanga or Bedford island and many more are shrinking as the rising water breaches the dykes and another dyke is built inside the previous, thus losing a part of the island.

"We've grown up seeing tides and ebbs in the rivers but now rivers rise much above the usual level and nibble at the bottom of the dykes to breach them," Kabita Patra says.

"Creating mangrove forest on the riverfront is the only way to stop embankment erosion and save lives. Mangroves hold the soil in the thick network of roots and soak more carbon di-oxide from the atmosphere," Director, School of Oceanographic Studies in Jadavpur University in Kolkata, Prof Sugata Hazra says.

Islanders are slowly realising the need to grow and protect the mangrove species like Baine, Geona, Hetal which otherwise they would fell for firewood and log.

As August ends, the residents of Madanganj village go out to collect the floating seeds of mangroves from the rivers and estuaries to plant them. Men collect mangrove seeds, dig trenches to collect mudbeds on the riverfront during high tide and women plant the germinated seeds on the mudbeds when the river ebbs.

Sunderbans Development Board and several NGOs have come forward to give money and technical expertise to the villagers to plant mangroves, which is being considered as the main protector of the dykes.

A research team led by Prof Hazra has found 82 square km land has gone under water in the estuarine island system over the past three decades.

The team found erosion and submergence have been taking place in the twelve sea-facing southern Islands of the Sunderbans in West Bengal, including the largest island of Sagar where a large number of pilgrims gather at Kapilmuni Temple during Ganga Sagar fair in January.