Mangrove forest destruction caused as much as 122 million tonnes of carbon to be released to the atmosphere globally between 2000 and 2015. As a result of 3,957 hectares of mangroves being deforested between 2000 and 2015, India ranked eighth worldwide for the amount of carbon stock loss.
However, since India has been effective in its efforts to curtail mangrove deforestation, it is also among the top 20 for the amount of soil carbon storage in mangrove forests globally.
Carbon stock refers to the amount of carbon stored in the forest ecosystem. It helps mitigate the impact of greenhouse gases, which lead to global warming and climate change. Soil carbon – the amount of carbon stored in soil – is the basis of fertility.
A study by USA-based think tank Woods Hole Research Center (WHRC), used satellite (30-meter resolution) remote sensing data to estimate soil carbon emissions.
According to the India State of Forest Report 2017 compiled by the Forest Survey of India (FSI), mangrove cover in India was calculated at 4,92,100 hectares, which 0.15% of the country’s geographical area. FSI estimated soil carbon stock for mangrove forests in India to be 3,979 million tonnes. Overall, carbon stock from all forests in India is 7,082 million tonnes.
Loss of soil carbon depends on how the land is used. Sanderman said, “Deforestation due to wood harvesting or conversion to rice will results in much lower losses of the soil carbon than conversion to shrimp aquaculture or draining, filling for urban development.”
In India, the study found that soil carbon storage in mangrove forests varied dramatically depending upon location.
“The Sundarbans in West Bengal have very low soil carbon stocks primarily due to the fact that there is high sediment input from the Ganges River system. A similar system is observed along the west coast of India. Whereas, mangroves down the coast in Tamil Nadu, such as the Pichavaram mangroves, contain almost four times as much carbon in a given hectare of forest due to low sediment deposition,” said Sanderman.