NASA study highlights loss of mangroves at creek near Mumbai over three decades
Two comparative satellite images show how mangrove cover has been destroyedmumbai Updated: Dec 10, 2017 00:31 IST
Satellite images from the National Aeronautics and Space Administration (NASA) have compared how the mangrove cover at Thane creek or Mumbai’s Flamingo Sanctuary has changed over the past three decades.
The two images juxtaposed together - one captured in 1988 and the other in 2017 - shows how urban development encroached on mangroves on the northern portion of the creek and the increase in area of the Deonar dumping ground ate into the southern portion of the creek, resulting in destruction of mangroves at the reserved forest (see images). The study was released earlier this month on NASA’s Earth Observatory.
The study incorporated reports by Hindustan Times from 2017 (see box) to identify the threats to the mangrove cover in Mumbai and Thane creek, cleanup of mangrove areas, proposed construction of a wall around Mumbai’s mangroves, using drones and satellites with the help of Indian Space Research Organization (ISRO) to monitor the coastal ecosystem.
“The Landsat images offer an example of how satellite imagery can be used to track changes to mangroves. These images are centered on Thane Creek — a key waterway that runs through the city. Both images were captured around high tide,” read the study. “Between 1988 and 2017, urban development encroached on mangroves in several areas. For instance, the Deonar landfill spread significantly, and new residential and commercial developments emerged along the northern stretches of Thane Creek.”
Mangrove forests have historically been overlooked in Mumbai, the study said. “Large tracts of mangroves were removed as part of land reclamation projects, and many of the mangroves that remain have become dumping grounds for garbage and targets for developers and squatters,” it read.
The study also took into account a research paper by the department of geography, Ryerson University, Toronto that examined the changes in Mumbai’s mangroves since 1970s. “We have seen stark declines in mangroves in Mumbai in recent decades. Of the entire mangrove system in the Mumbai Metropolitan Area, 36% has been lost to urban land since 1973,” said Eric Vaz of Ryerson University, author of the paper.
The Mumbai Mangrove Conservation Unit, under the state mangrove cell, was given the responsibility for the management of the Flamingo Sanctuary. When state mangrove cell was alerted about the report, they said a drive to remove encroachments from the northern end of Thane creek will be carried out between December and January. “We will be taking up the issue with the civic body about the rise in Deonar dumping ground area, eating into the reserved mangrove forest,” said N Vasudevan, additional principal chief conservator of forest, state mangrove cell.
The NASA images also illustrate a positive trend for the Thane creek with rise in mangrove cover at certain pockets owing to siltation. “Over time, the deposition of sediment has narrowed the channel and allowed some mangroves to spread closer to the center of the creek, even as research papers suggest long-term decline,” read the study.
“The Thane creek is currently a winter home ground for migratory birds such as flamingos, and if proper measures are taken to protect it, the creek will become a nesting ground for these birds. All our actions should work towards preserving the biodiversity and the ecosystem of this area and ensure there is no reduction in mangrove cover,” said Satish Gavai, additional chief secretary, state environment department.
Mumbai and Thane creek mangrove cover
Mumbai’s mangrove area spreads across 5,800 hectares (ha) of mangrove cover – 4,000 ha on government-owned land and 1,800 ha in private areas. While Navi Mumbai and the eastern end of Thane creek have a total cover of 1,471 ha, for the western bank of Thane creek it is 1,500 ha.
In August 2016, the state government declared the northern part of Thane creek that includes Airoli and Vashi as a Flamingo Sanctuary that is spread over 1,690 hectares, which includes 896 hectares of mangroves and 794 hectares of land adjacent to a water body, to safeguard the flamingo population.