Not conserved

The last frontier of the Bengal floodplains, the Sunderbans is a sprawling archipelago of several hundred islands, some large, some minuscule, stretching nearly 300 km between West Bengal and Bangladesh. It is part of the world's largest delta (80,000 sq km) formed from sediments deposited by three great rivers—the Ganges, Brahmaputra and Meghna—as they empty into the Bay of Bengal, and is also among the world's largest mangrove forests.

The region is crisscrossed by a maze of tidal rivers, estuaries and creeks that carry saline water nearly 300 km inland from the Bay of Bengal. The islands are low, marshy alluvial plains that are still in the process of being formed and reformed by continuous siltation and powerful tidal currents. What land the waters swallow from one end, they spit out as sandbanks and new islands at another.

The West Bengal part of the Sunderbans makes up 60 per cent of India's mangroves and comprises 102 islands, of which 54 are inhabited.Most of them were reclaimed and inhabited under the British, who, in the late 1700s, undertook a massive drive to clear the forests and make the land cultivable, so that people could be settled there and the government's revenues augmented.

Over two centuries of converting mangrove forests into paddy land, the exploitation of the area's natural resources, and hunting and poaching have all contributed to the degradation of this region, making it increasingly prone to erosion and vulnerable to storms and cyclones.

The 54 inhabited islands have no forest cover left. However, about 10,000 sq km of the Sunderbans are still covered by swampy mangrove forests (40 per cent of these lie in India and the rest in Bangladesh), much of which vanish under water for several hours a day during high tide. These dense, almost impenetrable estuarine forests have an amazing biodiversity. They are home to over 100 plant species and a variety of animals including Royal Bengal tigers, estuarine crocodiles, sharks, spotted deer, wild boar, Gangetic dolphins, otters, Olive Ridley turtles and numerous species of birds and snakes. These mangroves also act as a natural shield for the Bengal coastline, protecting it from storms, cyclones and tsunamis by absorbing much of their destructive force.

Sugata Hazra, director of Jadavpur University's School of Oceanographic Studies. His team's research on the Sunderbans has revealed the enormity of the catastrophe that is waiting to happen. Opting for understatement, he says climate change and tidal erosion are an "alarming development'. Unfortunately, the state is in denial

The Sunderbans, however, is best known for being the largest remaining natural habitat of the Royal Bengal tiger. It was the realisation that the big cat's numbers were fast dwindling that triggered India's wildlife conservation movement in the 1960s. By then, the changing landscape had already resulted in the disappearance of the leopard, wild water buffalo, Javan rhinoceros, one-horned rhinoceros, swamp deer, hog deer and several plant species. In 1973, the Indian government declared 2,585 sq km of the Sunderbans a tiger reserve under Project Tiger. In 1985, the area was included in unesco's list of world heritage sites and in 1989, India designated 9,360 sq km of Sunderbans a biosphere reserve.

Mysterious forest
While these measures helped safeguard what remained of the Sunderbans, they also helped promote its image as a mysterious and exotic forest. An image that relegated the region's human inhabitants to the background and obscured the fact that the Sunderbans supports a population of 3.9 million people, most of whom eke out a precarious living on these fragile, flood- and cyclone-prone lands by farming, collecting forest produce and fishing. This pit the protection and preservation of the mangroves against the needs of the local inhabitants. The population density here is high. Government figures peg it at 1,200 people per square kilometre.

Yet human settlements are hard to access, subject largely to the ebb and flow of tides and the availability of ferry rides. The 45,000 sq km of inhabited area has only 280 km of paved roads and a mere 42 sq km is accessible by rail.

On most of the islands, van rickshaws are the main mode of transport. Lack of basic infrastructure such as electricity, drinking water, hospitals and roads makes the Sunderbans one of the state's poorest regions. The per capita income here is Rs 10,000 a year.

As Sugata Hazra, jusos director puts it, the Sunderbans "is a unique case where the most socially and economically vulnerable population... lives on most vulnerable land'.

In the past 20 years, the sea has claimed two islands, Lohachara and Suparibhanga, the latter uninhabited. If scientists can be believed, Ghoramara and Sagar are following suit.

Mangrove factor: local warning on global warming
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Hazra and his team of researchers, who have studied the  region for several years, compiled a study—‘Preparatory Assessment of Vulnerability of the Ecologically Sensitive Sunderban Island System, West Bengal, in the Perpective of Climate Change'—in 2003 in which they say an annual 3.14 mm rise in sea level due to climate change is partly responsible for eating away these islands on the southern fringes of the Sunderbans. The higher than average rise in sea level (which is about 2.0 mm annually worldwide) is because of land subsidence (the caving in or sinking of an area of land through tidal erosion) which is typical of deltaic regions, Hazra says.

Other factors that contribute are:

• Depletion of mangroves. In 1885, the area of the Sunderban forests was about 20,000 sq km. Now it is about 9,600 sq km of which less than 4,200 sq km is mangrove forest

• Population: a 234 per cent increase since independence. At this rate, the numbers may reach five million by 2020 and 10 million by 2050, exceeding the system's carrying capacity.

• Reduction in sediment supply from the rivers: silt gets blocked in the dams built along these rivers up north

• 3,500 km of man-made embankments that, while protecting the island from erosion, prevent silt deposition and hamper islands' vertical growth. Most of the rivers draining into the Sunderbans estuary have lost contact with their original sources, and there is hardly any inflow of freshwater. During high tide, seawater inundates the islands, but river water finds no ingress because of embankments.

This causes salt deposition, which hampers cultivation and mangrove regeneration

All these factors, in turn, "make the system even more vulnerable to any further bio-geophysical perturbation related to climate change', Hazra and his team report.

Using an analysis of 15 years of tide gauge data from the Sagar island observatory, the researchers deduced that at this rate, the mean sea level in Sagar and adjoining areas of the Bay of Bengal would rise 20 cm by 2050. Club this with a corresponding rise in temperature over land and sea (the observed rise over the Bay of Bengal is at the rate of 0.019°c per year, which adds up to 1°c by 2050) and change in rainfall patterns (they found a "marginal increase' in monsoon and post-monsoon rainfall over the past decade but didn't detect any definite pattern), and "there's a strong probability that the sea level will rise by 50 cm at that time', they say.

The scientists, through statistical analysis of erosion and accretion rates of the Sunderbans islands and mathematical correlation studies, have found a link between relative rise in sea level and higher coastal erosion rates in the region. Based on this, they have identified the 12 southernmost islands in the region (including Ghoramara) as "most vulnerable in terms of coastal erosion, submergence and flooding'.

Data from the state irrigation, forest and agricultural departments as well as local government records indicate that property worth Rs 130.6 crore and about 485 lives have been lost in the past two decades. "These numbers,' says Hazra, "are likely to increase manifold in the future.'

Hazra says his team's study is a "preliminary assessment', but he insists that climate change is affecting the Sunderbans'. He calls it an "alarming development'.