mumbai

Updated: Aug 05, 2019 01:09 IST

Mumbai has set aside 224 hectares (ha) of mangroves as reserve forests. About 40 ha of these newly-protected areas are along the Mithi river, which is choked by illegal construction. Other forests that have received protection are in Charkop, Vikhroli and Versova, locations that are threatened by encroachers. The latest notification brings the total mangrove forests under protected status to 3,948 ha — almost 40 square km.

Areas notified as reserved forest under the Indian Forest Act, 1927, get better protection from destruction and encroachers.

The International Union for Conservation of Nature says mangrove forests, along with other coastal wetlands like tidal marshes and seagrass meadows, are long-term carbon sinks, storing carbon in the plants themselves but more importantly in the soils below for thousands of years. This process is called carbon sequestration and it can help control global warming by reducing carbon dioxide (CO2) levels in the atmosphere, according to scientists.

These ecosystems also are important in coastal protection, habitat, food security, biodiversity and tourism. The world is losing coastal wetlands on a large scale.

Studies have shown that the city is losing its mangrove forests. A study by Godrej & Boyce estimated that private mangrove forests in their industrial estate in Vikhroli absorbed 50,000 tonnes of CO2 annually. It found that mangroves and the soil they are rooted in have absorbed thousands of tonnes of CO2 from Mumbai’s air, effectively cleaning the air of emissions released by vehicles, industries and unsafe burning of wastes. The study showed that mangrove cover in this area has increased, leading to an increase in biodiversity.

An earlier study by the Thane-based BN Bandodkar College of Science found that mangroves along the Thane creek store 2,38,417 tonnes of carbon. To study the carbon content, researchers collected fresh and fallen mangrove leaves from creek sides in Bhandup and Airoli. A study called ‘Carbon footprints of 13,000 cities’ in 2017 estimated that the Mumbai Metropolitan Region, which has a population of over 20 million, released 32 million tons of CO2 annually, with a per capita emission of 1.5 tonnes. Mumbai’s per capita CO2 emissions are low compared to New York’s 17.1 tonnes and London’ 10.4 tonnes, but as vehicle ownership increases and electricity consumption rises, the city’s greenhouse gas emissions will go up.

Much still needs to be done to save Mumbai’s mangrove forests. According to the Bombay HC order of September 18, 2018, approximately 700 ha have to be given the status of reserve forests. After the recent notification on 224 ha of mangrove cover, 475 ha remain unprotected. The forest department says they are in the process of identifying locations that need protection. As per the Forest Survey of India, Mumbai has 6,600 ha of mangrove cover, with 6,400 ha in the suburbs and 200 ha in south Mumbai. Of this, close to 4,500 ha is on government-owned land and remaining in private areas.

Mumbai has overlooked and abused its mangrove forests and before environmental laws became more stringent, destroyed large tracts for land reclamation projects, slums and dumping sites. Landsat images from 1988 and 2017 show the destruction of mangroves along Thane creek, with the expansion of the Deonar garbage dump and new construction. The Forest Survey of India estimates that Thane creek still has more than 59 sq km of mangroves.

There is a debate about the health of Mumbai’s mangrove forests. Some environmental groups have said that about 70% of Mumbai’s mangroves have been destroyed due to various development activities, but satellite imagery, which has recorded decline in mangrove forests in many areas, have also reported another development. Sedimentation is narrowing Mumbai’s waterways, including the Thane creek. The new mudflats created by the sediments are being colonised by mangroves, thus expanding the green cover in certain areas.