New research claims rising sea levels are not a threat to the Sunderbans

Kolkata: As new islands are still taking birth in Sundarbans delta through a natural process of erosion and accretion, rise in sea level due to global warming is not a major threat to survival of the archipelago, claims a new research, contradicting previous studies. "Compared to the much publicised belief, the islands of Sundarban are not facing similar threat from the impacts of global warming.

"While the predicted sea level rise will have marginal impact on the Sundarban islands having mangrove cover, formation and emergence of new islands, through accretion and deposition of silt load, gives a new dimension to the profile of this estuary," says a report by a group of foresters and scientists. Atanu Raha, the lead author of the study, also the former principal chief conservator of forests of the state, points out that if sea level rise is at play in the Sundarbans, then the effect of shrinking will be noticed on all sides across islands.

"But in some places we see erosion and at others we see accretion. So it means the net loss of land is due to a natural process of formation of estuary and delta through the cycle of twice a day floods," Raha told PTI. An archipelago group of 102 islands, the low-lying Sundarbans delta is home to 42 lakh people and also 76 tigers, according to the last census. Based on the UN's climate science body IPCC's report that the sea had risen on an average by 3.2 mm per year since 1993, a number of research reports had so far claimed the sea level rise is causing havoc in the Sundarbans, a UNESCO World Heritage site.

After the loss of Lohachara and Suparibhanga islands in the last two decades, the Sundarbans came to be known as the 'vanishing islands.' The researchers contradicted the theory by analysing satellite imageries from the National Remote Sensing Centre, Hyderabad. The report emphasises that general predictions of gradual vanishing of the Sundarbans due to sea level rise may be a bit too far extension of the "imaginary threat" as the dynamics of this estuary has made it extremely resilient. A study of island formation process for Thakuran Char shows the island started coming up only in 1986 and since then it has matured into a beautiful mangrove forest island of more than two sq km.

Similarly, large 'char' (accretion) lands have come up in the coastal regions near Kalas, Chaimari and Baghmara under the Sundarban tiger reserve, while erosion of river banks and coastal region has taken place in Goasaba blocks and Sagar island. Many small islands like New Char, Haribhanga etc. have come up within or just outside the estuary over the last few decades. Lothian island also has shown gradual increase in size over the years. "Sundarban estuary is still in the process of formation. As per the natural process, silt carried from the catchment of the rivers draining into the estuary, get deposited and islands are built up," the report says.

Simultaneously, because of tidal waves and oceanic current, shape of the islands keeps on changing as accretion and erosion go hand-in-hand. The Sundarban estuary is acting as a sediment sink and may be largely offsetting the effects of sea level rise in terms of land loss, it says. A three-hour drive from Kolkata, Sundarbans is a complex network of streams, rivers, tidal creeks and channels.