Less than 1% of India’s mangrove cover deforested in 15 years: Global study

Mangrove cover over the Mumbai region (WOODS HOLE RESEARCH CENTER, EUROPEAN SPACE AGENCY)
Mangrove cover over the Mumbai region (WOODS HOLE RESEARCH CENTER, EUROPEAN SPACE AGENCY)

India has the 10th largest mangrove cover in the world and according to a recent study, less than one percent of it was deforested between 2000 and 2015.

“We found that less than 1% of the Indian mangrove forests were deforested between 2000 and 2015 (4,000 ha). This rate of loss is only half the global average, meaning India has done an excellent job since 2000 of protecting its remaining mangrove forests,” said Jon Sanderman, lead author of a study of the state of mangroves all around the world.

Published earlier this month (May 2018) by USA-based think tank Woods Hole Research Centre (WHRC), the study analysed satellite maps and found that of the 4,52,676 hectares of mangrove forests in India, only 0.87% or 3,957 hectares were lost over 15 years. Globally, 1.67% of the world’s mangrove cover was lost.

Although India is in the ninth place globally for maximum mangrove area lost between 2000 and 2015, it has been able to conserve its mangrove forests better than other countries on the list. Indonesia is in the top spot, with a loss of 1.15 lakh hectares, followed by Malaysia, Myanmar, Brazil, and Thailand.

Mangrove swamp, partly underwater image showing the root system
Mangrove swamp, partly underwater image showing the root system

Sanderman said there is usually pressure to develop mangroves for urban or agricultural uses because mangroves tend to occur in locations with high human population density. “Mangroves surrounding large cities such as Mumbai have been lost primarily due to urban growth. Natural disasters such as tsunami led to mangrove loss in southern regions such as Tamil Nadu, Odisha and Puducherry. In other regions, conversion of mangrove areas into aquaculture farms or for fuel wood harvesting are the primary drivers of forest loss,” said Sanderman.

According to the central government, the current mangrove cover in India amounts to 4,92,100 hectares.

Sanderman emphasised the need to conserve mangroves because they help mitigate climate change and are critical nursery habitats for fish, birds and marine mammals. Mangroves also act as buffers from storms for coastal communities and even benefit them economically. “It is estimated that the mangrove ecosystem service benefits are at an average of $4,200 US per hectare per year in Southeast Asia,” said Sanderman.

Carbon stock loss in mangrove forests: India ranks 8th

A map of the Indian Sunderbans, showing the boundaries of the protected areas, conservation and lodging centres, subsistence towns, and access pointsMangrove 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.

WHRC used satellite (30-meter resolution) remote sensing data to estimate soil carbon emissions.

“Our analysis revealed that soil carbon stored in mangrove forests across the world holds more than 6.4 billion tonnes of carbon globally, which is about 4.5 times the amount of carbon emitted by the US economy in one year,” said Jon Sanderman, lead author of the study and associate scientist at WHRC.

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. (Hindustan Times)

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