If the current situation prevails for a couple of more years then Sunderban will be known as Goranban. Sundari trees (Heritiera fomes), from which Sunderbans derives its name, is reeling under great threat with the rise in sea level and subsequent increase in the salinity of rivers that feed Sunderbans.
Of the 60 varieties of mangroves and mangrove associates that are found in India, the Sunderbans accounts for 50, many of which are rare. Known for its biodiversity, the region has been identified as a World Heritage Site by the International Union for the Conservation of Nature. But with the increase in the salinity many fresh water mangroves are being replaced by more salt-tolerant species like Ceriops decandra (Jhanti Goran) gradually colonizing the saline blanks.
Forest officials claim that indiscriminate felling of trees has been stopped totally. But substantial increase in the region’s population had led to the exploitation of the Sunderbans. In 1951, the area’s population was 11,59,559; by 1991 it had risen to 32,05,552. Today it stands at approximately 40 lakhs.
The villagers are not the only one to be blamed for this catastrophe. “There is a major racket being run in the Sunderbans by timber merchants, who bribe forest officers and workers and get a free hand in collecting as much timber as they wish,” said a member of a local NGO working in the Sunderbans. He further added that Sundari tree has become one of the prime targets of the timber merchants and is vanishing.
The ecological significance of the Sunderbans is immense. Apart from serving as a shield against natural calamities, it checks atmospheric pollution. It has a seemingly unlimited capacity to absorb pollutants from both air and water. A recent study revealed that every day more than 23 kg of pollutants are dumped into the estuaries in the Sunderbans. Untreated urban waste and oil slicks from passing tankers could also cause an unmanageable disaster. Although the Sunderbans has an enormous capacity to absorb industrial effluents and other forms of pollutants, experts feel that if the present situation continues for long, it might affect the ecosystem adversely.
Atanu Kumar Raha, State’s Principal Chief Conservator of Forests, said: “About 220 sq km of land area has been eroded away in Sundarban Tiger Reserve only, over a period of 70 years till year 2000. Southern parts of Jambudwip, Mayadwip 4 and 5 compartments and south-eastern part of Goasaba Block are suffering progressive erosion. While accretion/new formation of Char land are taking place at South Sagar Sand, lower long Sand islands in Muriganga estuary, in Muriganga, Saptamukhi and Thakuran rivers within the boundary of Reserved Forest.”
“Even 150 years ago, the Sunderbans was the home of the one-horned Indian rhino, the Javan rhino, wild buffaloes and even river dolphins. All these are now extinct,” Raha said.
The rivers Matla, Saptamukhi and Thakuran have practically no connection with their original mother streams and are now inlets of the sea. The sources of all the rivers in the western part of Sunderbans have been progressively silted up, thus disconnecting the inflow of fresh/sweet water into the mangrove delta. This has resulted into increased salinity of the river waters and making them shallower over the years.
On the other hand, during the ebb tides, the receding water level causes scouring and creates innumerable number of small creeks, which normally originate from the centers of the islands. The receding water, while draining into the Bay of Bengal, carries large volumes of silt load. This silt, on the other hand, gets deposited along the bank of the rivers and creeks during high tide, resulting into increase in height of the banks as compared to interior of the islands. As a result, high tide cannot normally reach the interior of home of the islands.
Mr Raha said: “Construction of a large number of dams and barrages in the Damodar river catchments and the Ganges has resulted into decreased silt load and lesser deposition of the debris in the down stream and into the estuaries. Most of the rivers draining into the Sunderbans estuary have lost contact with their original sources, and there is hardly any inflow of fresh/ sweet water with silt load into the Sunderbans. During the peak high tide, highly saline sea water inundates the numerous islands while during other times, the water fails to reach the interior of the islands due to raising of bank levels and due to lack of normal fresh water flow in the river systems.”
“On the other hand, during the ebb tide, the receding water from the interior of the islands scour the top soil and from channels connecting with the rivers/creeks. These eroding actions of ebb tides are more prominent in some of the islands of Sunderbans as compared to others. With passage of time, these eroded channels keep on extending further inwards and result into formation of muddy blanks. As these blanks are not regularly flooded by high tides, capillary action of the clayey soil and excessive heat during dry time results into deposition of salt crust at the surface and turns them into saline blanks and prevents natural regeneration of mangrove species,” he explained.
An official of the Propagation Centre for Endangered Mangroves at Jharkhali, Sunderbans, said that prawn seed collectors have done considerable harm to their efforts to replant mangrove. Over two lakh people in the Sunderbans are engaged in collecting tiger prawn seeds, using nylon nets, which are dragged along the river banks. In the process, apart from destroying mangrove seedlings and eliminating the possibility of a regeneration of mangroves along the river banks, at least 74 species of fish are also destroyed.
A survey conducted in 1994 by the S.D. Marine Biological Research Institute, 24-Parganas (South) revealed that on an average in the process of collecting 519 prawn seeds, at least 5,103.25 gm of other seed varieties that sustain different categories of fish are destroyed.
The steady destruction of so many varieties of fish, in turn, has adversely affected animals, which depend on them. It is also threatening to endanger the different species of crocodiles, which form one of Sunderbans’ major attractions.
Sundari trees that constitute about 70% of the forest have been dying for the past 30 years, while 20% are afflicted with a disease that kills the trees from the top down. Experts are not ruling out the possibility that the Sundarbans will be completely destroyed unless destructive human activities are stopped and better monitoring of environmental degradation is conducted.