Mumbai’s mangrove cover up by 20% in 15 years, reveals study
The mangrove cover in Mumbai increased from 55 sq km in 2000 to 65.9 sq km in 2015 — a 20 percent rise — a satellite study by the National Institute of Oceanography (NIO) revealed. Mangrove forests cover one-tenth of Mumbai. In 1972, there were just 45.3 sq km of mangroves in Mumbai.
The study was released on World Mangrove Action Day on Wednesday at the Silver Jubilee National Mangrove Conference at Dona Paula, Goa, by the Mangrove Society of India and NIO.
Thane, Sewri-Mahul and Mahim creeks have seen a rise in mangrove forests. However, Malad creek, which covers locations such as Versova and Oshiwara, and other areas of Andheri have seen a drop in mangrove cover.
The figures from NIO are significantly higher than estimates by the state mangrove cell in Mumbai. According to the mangrove cell, Mumbai has 54.7 sq km of mangroves. NIO officials said that considering the number of mangrove destruction cases in 2016-17, the mangrove cover has declined by less than 1 sq km.
Speaking at the conference, Dr R Mani Murali, senior scientist, NIO, said, “Apart from Andhra Pradesh, parts of Sunderbans in West Bengal and Andaman and Nicobar Islands, there has been a rise in mangrove cover across the country. For Mumbai, areas from Sewri to Thane have seen a high sedimentation over the past decade, which has allowed the development of mudflats and more mangrove trees.”
Spread over 1,690 hectares, the northern end of Thane creek was notified as a protected flamingo sanctuary in 2015. It is home to 10 mangrove species and over 200 bird species.
Murali’s findings are a part of an unpublished study, currently being peer-reviewed. The satellite information was collated using remote sensing technology (Landsat satellite images) by NIO over the years. “Satellite remote sensing and Geographical Information System (GIS) is a very useful technology. It needs to be adopted by all state governments for real-time detection of mangrove destruction,” he said.
He added that apart from natural causes there were a number of minor reasons that have helped mangroves thrive over the past five years.
“While laws are very strict now and authorities are vigilant, there is more awareness among people to raise issues related to mangrove destruction,” said Murali.
On October 6, 2005, the Bombay high court banned construction or reclamation within 50 metres of mangroves.
The mangrove cover of Goa and Odisha have also increased. In Odisha, it increased from 206.7 sq km in 2010 to 222.92 sq km in 2015 while Mandovi in Goa has seen an increase from 149.45 ha to 1,059.77 ha in the same period. The cover grew from 142.95 ha to 676.12 ha along Zuari (including Cumbarjua canal) in Goa. “Our attempt now is to document mangroves species using remote sensing,” said Murali.
The Mumbai Metropolitan Region will lose 106 hectares of mangrove forests, which equals 72 Wankhede Stadiums, for the proposed Navi Mumbai airport. Also, 33.17 hectare of reserved mangrove forests will be lost at the northern side of the Coastal Road Project — almost
three-and-half times the size of Oval Maidan (9 ha) in south Mumbai.
N Vasudevan, additional principal chief conservator of forest, state mangrove cell, said, “The reason why the increase is visible is that because of siltation, the creek is getting narrow and allowing the growth of new mangroves on both sides. We have also protected mangroves over the past five years.”
“Wanton destruction of mangroves, which was earlier widespread, has come down as more people are aware of the law. However, dumping of debris and proliferation of slums within mangroves need to be controlled.”
Meanwhile, some environmentalists expressed scepticism about the study. “Instead of dispersing, the silt is stagnating and accumulating in one part. While mangroves might be growing, these areas will become mangrove swamps and reduce the number of places where flood water and sewage can discharge,” said Stalin D, director projects, NGO Vanashakti.