Having 2,118 sq km of total mangrove forest cover, the Indian Sunderbans have soaked in 4.15 crore tonnes of carbon dioxide, valued at $79 billion in the international market, researchers from the University of Calcutta said.
“Mangrove trees act as a natural tank for carbon dioxide storage and absorb carbon for their own needs. The more such biomass we have on the earth, the more CO2 will be pulled from atmosphere, ultimately resulting in controlling the rise of atmospheric temperature and the subsequent climate change,” Prof Abhijit Mitra, who led the research, told Deccan Herald here.
The process of removing carbon from the atmosphere and depositing it in a reservoir is known as carbon sequestration. As a primary greenhouse gas, large-scale CO2 emission is responsible for global warming as it leads to a rise in sea levels and temperature, affecting agriculture, fisheries and human health.
With funding from the Union Ministry of Earth Science and the state forest department, the two-year-long study of the carbon sequestration efficiency of the mangroves was done by the university's marine science department.
Of the total amount of carbon tied up in earthbound forms, an estimated 90 per cent is contained in the world's forests. For each cubic foot of merchantable wood produced in a tree, it has been estimated that about 15 kg of carbon is stored in total tree biomass.
To evaluate carbon stocks in the above-ground biomass of three dominant mangrove species (Sonneratia apetala, Avicennia alba and Excoecaria agallocha) in the Sunderbans, carbon content in stem, branch and leaf biomass was estimated using laser beams. The estimates done in the study, however, exclude the below-ground biomass found under the soil.
Atanu Raha, the state's principal chief conservator of forests, said in the core forest area, there has been no degradation due to human intervention. Only a few forest trees have been lost due to natural reasons beyond our control.
The study has also found that the central part of the Sunderbans is a poor carbon sink as compared with the western part of the delta.
“The fresh water of Himalayan glaciers fails to reach the central part due to heavy siltation and clogging of the Bidyadhari channel. This has affected the growth of productive mangrove vegetation,” Mitra said.
Effective soil management, tidal interactions and sufficient flow of fresh water into the mangroves can improve the biomass production of mangrove species. If the social forestry project is taken up extensively in the Sunderbans, it might even help the government earn carbon credit points and sell them for cash using the carbon emission trading system under the United Nations Framework Convention on Climate Change.
“Himachal Pradesh has already done it. In the international market, one tonne of carbon is valued at $19. So the Sunderbans can be valued at around $ 79 billion in terms of the amount of carbon dioxide it sequesters,” Mitra pointed out. The carbon trading system has been recognised by the UN as a method to reduce greenhouse gas emissions by giving it a monetary value.
