‘MMR has lost 107.6sqkm of waterways and agricultural land’
The Mumbai Metropolitan Region (MMR) has lost 107.6 square kilometre (sqkm) of waterways and agricultural lands along its coast between 1990 and 2019, according to preliminary results from an ongoing study by Pune-based NGO Srushti Conservation Foundation (SCF). The cumulative area is larger than Sanjay Gandhi National Park, which encompasses 103sqkm.
The SCF study is led by Dr Deepak Apte, former director of the Bombay Natural History Society (BNHS),
Due to increased rate of siltation over the past 30 years, Apte explained, these areas have now turned into mudflats or mangrove forests, leading to shrinking and even shallowing of the city’s creeks. About 47sqkm area has been lost in the Mumbai-Thane creek itself, which in the future may pose a threat to the area’s avian biodiversity (including flamingos). The coasts in Mumbai, Thane, Navi Mumbai and Uran have all been affected by this process.
“As a result, existing waterways and coastal lands may turn into extremely shallow swamps or even dry lands in many parts, which will become unfit for navigation, reduce their storm water drainage capacity, and render the habitats unsuitable,” Apte said, warning that there will also be consequences for urban flooding.
Shrinking creeks spell bad news for Mumbai, especially at a time when previous studies have indicated rising sea levels of 0.5 to 3mm per year in the Arabian Sea, along with of extreme rainfall events in the foreseeable future.
Simply put, shallow creeks cannot hold as much water; so even with a slight increase in sea level rise and precipitation levels, the combined impact of high-tide and heavy rainfall with lead to a spill-over of water into the city, disrupting the lives and livelihoods of coastal populations and exacerbating degradation of otherwise productive coastal lands.
Apte recommended that the National Centre for Coastal Research (NCCR) under the Ministry of Earth Sciences be roped in for “drawing up a comprehensive plan for conservation/ restoration of the ecosystem using scientific study”. NCCR, in collaboration with the Brihanmumbai Municipal Corporation (BMC), last year developed a flood warning system called i-flows for Mumbai to mitigate adverse impacts during monsoons and extreme weather events.
To be sure, this is not the first time that researchers have attempted to make an assessment of Mumbai’s shrinking waterways. As yet unreleased data from the mangrove cell under the forest department found that Thane Creek has shrunk by an average of 0.6sqkm every year between 1972 and 2020. The unpublished study also found that in a business as usual scenario, the mouth of the Ulhas river may entirely shut in the next 30 years, by 2050. Published studies, such as one from January 2020 in the Journal of Coastal Conservation and another by the Salim Ali Centre for Ornithology and Natural History (SACON) and the BN Bandodkar College of Science, Thane, have also noted or demonstrated the siltation issue.
“Considering the seriousness of this issue where the width of creeks are reducing owing to excess siltation, scientific removal of mangroves will have to be carried out to protect the original coastline. SCF’s findings seem to be accurate as mangrove cell has also carried out a similar internal satellite mapping study of Thane creek, which shows tremendous rise in mangroves with the width of these waterways decreasing. We are fine tuning this report and it will be published soon,” said Virendra Tiwari, additional principal chief conservator of forest (mangrove cell) and executive director, Mangrove Foundation.
SCF’s analysis shows that surface waters across Mumbai and Thane creeks along the eastern seafront dipped from 400sqkm in 1990 to just over 350sqkm in 2019. However, between 1995 and 2019, the average flamingo population, as reported by BNHS in multiple releases to the press, rose from about 20,000 in 1995 to about 120,000 in 2019.
“Flamingos and migratory waders are presently benefiting from the shrinking waterways as their population increase is being witnessed in the same trajectory as the expansion of mudflats and mangroves. This in combination with high sewage load that MMR is pumping into the creek as well as warm water from refineries and power plants make it a perfect feeding ground, with nutrient rich flora and fauna,” said Apte.
Another factor aiding the abundance of flamingos (in Thane Creek and satellite wetlands in Navi Mumbai) is the loss of other wetlands in MMR and Uran, which has reduced their available space. The Thane Creek, Apte said, is still relatively safer and cut off for the birds. However, once the accreted land is taken over by mangroves in combination with reduction in tidal prism during non-monsoon months, soft mudflats turn into hard and barren land. “Thus, flamingos could permanently move away from the area,” he said.