Sundarbans, the world’s largest mangrove forest
By Kazi Motahar Rahman
As unknown disease has struck the world’s largest mangrove forest.
More worrying is that the awesome disease is killing the spices which make up more than half the tree population of Sundarbans off Khulna coast.
The disease catches the Sundari trees, after which the forest is named, from the top. Leave and branches are the first to get dry before finally choking the roots to the bewilderment of experts.
Scientists have named the disease “top-dying” but failed to pinpoint, despite, series of studies, what really causes it.
“The cause is yet to be identified,” says Latifur Rahman, a researcher at the mangrove Culture Centre in Khulna.” There are several hypotheses, however, with the growing salinity in rivers along the forest being the major suspect. Experts are yet to detect the cause and prescribe the remedies, Sundari population is fast withering. According to forest officials, top dying has already destroyed nearly 20 percent of the Sundari Plantation, while 50 percent are clearly endangered.
Zinnatul Islam, senior Scientific Officer of Bangladesh Space Research and Remote Sensing Organization, recently conducted a study on the Sharankhola range of the Sundarbans. He found 17 per cent of Sundaritrees destroyed. He also detected that 50 percent of the sundari trees in the range has been afflicted by the aliment.
According to a 1956 survey by the Forest Department, Sundari trees covered 60 per cent of the total area of the Sundarbans. The percentage dwindled to 53 per cent in 1994.
The forest department points to the Farkka barrage that India has built on the river Ganges.
The dam severely limits downstream flows of the rivers to the Bay of Bengal along the sundarbans causing salinity upstream.
Salinity in the rivers are thus rising, and experts find a logical link between the top dying and rising salinity in Sundarbans rivers.
“Sundarbans is purely a mangrove forest. Salt water flushes most part of it twice a day. So the volume of salt in water must have a great impact on the forest spices,” said one forest official.
For normal growth of Sundari trees, the water, must contain 12 part per Trillion (a measurement of salt in water and soil) and soil must contain between 8 and 10 PPT. But the latest study shows that Sundarbans river now contain upto 28 PPT salt, specially during dry season, while the soil contains between 16 and 20 PPT.
Experts find the salt ratio dangerous for survival of the sensitive mangrove spices.
One foreign experts, Dr. Gibson once said repeated natural calamity, excess salinity and massive silatation in and around the forest might be causes of top dying disease. Her recommended chopping of the upper portion of the effected trees to prevent it.
As per Gibsons prescription, the Government has cut off about two million cubic feet of the affected Sundari plantation.
Situation has not improved much.
With top dying threatening the Sundari population, forest officials see it a major blow to the forest resources.
` “This is not only a big threat to the forest itself, also to the economy. Sundari trees account for 60 percent of the marketable timber in the Sundarbans and a major source of fuel wood in southern region,” one forest official said.
Forest officials and experts are worried about the disease spreading to ther spices gradually and cause a disaster in mangrove ecology.
Said prof M Aminul Islam of University of Rajshahi: “Many animal spices are facing extinction besides trees, because of abnormal level of salinity. All these will inevitably lead to an utter imbalance in the eco-system. An environmental disaster looms large.”
Researcher Rahman cautioned that the Sundarbans mangrove might be a “thing of the past” like Chokoria mangrove unless something is done urgently to put a break on the dying process.
“We hardly can afford to lose the sunderbans when total forest area is far less than the required level,” he said.
The government claims 16 per cent of Bangladesh is forest but unofficial estimates put the figure at below 10 percent, environmentally unsafe.