Shahenoor Akther Urmi

The ecosystem of the Sundarban has drastically changed compared to 20 years ago and if it continues the forest will lose almost 29 percent of its productivity within 2050. Climate change, especially salinity, is one of the main reasons behind the damage while the numbers of big trees are declining gradually, Dr Swapan Kumar Sarkar, Professor of Forestry and Environment Department, Shahjalal University of Science and Technology was explaining his recent visit to the mangrove forest Sundarban.

In his newly published research paper called ‘Salinity reduces site quality and mangrove forest function. From monitoring to understand’ Dr Swapan along with other researchers observed that Salt-intolerant climax species like Sundori declined in high saline areas, while salt-tolerant species like Gewa and Goran trees increased.

The mangrove forest is called Sundarbad because of the tree name ‘Sundori’ and the number of the tree has been declining, so he chose the forest.

Salinity also decreased species-specific leaf area, whereas wood density has been increasing, Dr Swapan said, adding that added, salinity increases significantly impede forest growth, resulting in less productive ecosystems dominated by dwarf species and reducing stand structural properties, soil carbon and macronutrient availability in the soil.

In another researched paper titled ‘solving the fourth-corner problem: forecasting ecosystem primary production from spatial multispecies trait based model’ Dr Swapan along with two more researchers had applied integrated approach and find that the world’s largest mangrove forest’s ecosystem impacted simultaneously by climate change and multiple types of human exploitation. The paper also adds that Changing seawater levels from the south and freshwater damming from the north cause extensive variations in the Sundarbans’ environmental variables, such as salinity and siltation.

Muhammad Abdur Rahaman Rana, an environment scientist said “Sundarban is situated on the Ganges estuarine of the triangular shaped Bay of Bengal and the continental shelf of the Ganges estuarine flows to the Bay of Bengal sharply. As a result, brackish water can easily access the coastal areas of Sundarban and its adjacent land areas.”
“Brackish water intrusion has increased recently in Sundarban due to sea level rise and exploitation of the natural ecosystem and adjacent water bodies. So, biodiversity of the forest and rivers of the areas cannot tolerate high salinity,” he said, adding that almost 195 species of different fishes, trees, flora and fauna have already faced extinction from the Sundarban areas.
Meanwhile, brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with freshwater, as in estuaries, or it may occur in brackish fossil aquifers.

Abdur Rahaman, who is the Director of Center for People and Environ also said that fresh water fishes are declining fast in Sundarban while some of them migrated themselves from the area as the salinity is likely to adversely affect their reproductive cycle and capacity, extent of suitable spawning area and their feeding and breeding.

According to the World Bank Report, the different salinity tolerance ranges for 14 varying dominant mangrove species detected in 2013 satellite images of the Sundarban with the expected salinity for alternative scenarios of climate change by 2050.

The report also relieved that the Sundarban’s ecosystem induced by rising salinity are likely to change the prospects for forest and fishery-based livelihoods, resources should be directed to the development of alternative livelihoods for ecosystem-dependent households.

Mohon Kumar Mondol, Executive Director of Local Environment Development and Agricultural Research Society (LEDARS), said “scanty rain and increased salinity are also reasons for the losses of livelihoods and fishes. Monsoon becomes one month and sometimes due to heavy downpour, floods damage crops and paddy fields.”

He also said people of Shyamnagar upazila under Satkhira district have scanty fresh water. Some tube-wells and ponds are the main sources for fresh water but those are insufficient for the area.
Soil salinity is likely to lead to a significant decline in the output of high-yielding varieties of rice which ultimately impacts on the poor farmers’ livelihood.
Mondol said, “The Government has allocated a budget to the Union Parishad under the Ministry of Local Government, Rural Development and Cooperation for development. But Chairmen are focusing on infrastructures rather than fresh water resources.”

Edited By-SPT