For the past three years, a group of 20-25 researchers and field workers have lived at the Bombay Natural History Society (BNHS) field station in Airoli, which was set up in 2017 to conduct scientific studies in and around Thane Creek and Navi. to enable Mumbai. For three consecutive days a month, depending on when the tides are most favorable, the researchers set out to study 46 kilometers of marshes that line the banks of Thane Creek, a coastal cove off the city’s eastern waterfront separating them from the mainland of Maharashtra.
Armed with rubber boots, life jackets, binoculars, cameras and various data sheets, the group breaks into smaller teams at the Airoli jetty. Some team up with local fishermen who help them wade into the tidal flats on long wooden planks, where researchers use a tube-like device called a grapple to extract columns of the loose, slushy sediment that makes up the creek’s tidal flats. Each excursion lasts between three and five hours. Samples and data collected on site are then returned to the BNHS campus for laboratory evaluation.
During the months when flamingos and other migratory shorebirds arrive to feed on the algae, cyanobacteria and small crustaceans living in the streambed, the group ventures into deeper waters to count, photograph and monitor these birds in their habitat observe. The ultimate goal, the researchers explained, is to create an evidence-based conservation plan for the ecology of Thane Creek, which many believe is at risk from pollution and upcoming infrastructure projects.
It is also part of an ongoing long-term study – the first of its kind – to assess the populations and behavior of flamingos and other wading birds in Thane Creek.
Closing the gap
Flamingos have flocked to Mumbai for nearly three decades, and although experts claim they likely visited them earlier in smaller groups, the first large gathering (around 8,000 birds) was not observed until 1994. Their numbers have since risen to hundreds of thousands and migrate annually from their breeding grounds in the Rann of Kutch to the countryside in and around Thane Creek, usually arriving in November and staying until early June.
Otherwise, little is known about why they visit them and how they relate to the city’s environment.
The BNHS conducted a preliminary assessment of the area’s bird species diversity and produced a report in 2015 when it was commissioned to conduct a 10-year study on the Mumbai Trans Harbor Link (MTHL) – a 22 km long bridge to be built across the mouth of Thane Creek from Sewri in southeast Mumbai to Chirle in uranium in the Raigad district – received the go-ahead.
In September 2015, before then Prime Minister Devendra Fadnavis visited Japan to meet with the main sponsors of the project – the Japan International Cooperation Agency (JICA), the state accepted a key condition set by the Union Ministry of the Environment, excluding those of MTHL the mandatory environmental approval (EC) required for the start of the work would have been refused.
The condition was that a long-term monitoring study of flamingos and other shorebirds in Thane Creek be outsourced to BNHS, which would track their numbers in parallel with the construction and operation of the MTHL. The BNHS study (which started in 2017) will be completed in 2027.
Get to know waders
The researchers highlighted four general goals of their ongoing study. First, they are trying to gauge the true extent of the creek’s flamingo population, with recent estimates ranging from 100,000 to 150,000 per year. The second is to assess the availability and distribution of food in the creek’s Wadden Sea.
The third goal is to learn more about the flamingo’s hiking trails. Although mostly native to Gujarat, researchers now believe that some birds fly over from Kazakhstan and Iran as well.
A total of 39 birds in the stream were marked with aluminum rings with unique ID numbers and can be seen again in other countries. Two birds tagged in Mumbai have been tracked from Tamil Nadu and Rajasthan in the past two years, and researchers also plan to tag around 10 flamingos with radio collars by December 2021.
Finally, the researchers also hope to understand the relationship between birds and the stream. You now know that the birds are used to feeding grounds and that a group of flamingos look for food in the same place every day. Researchers also know that the largest groups congregate in Sewri, Mahul and Airoli and that they use satellite wetlands in Bhandup, Navi Mumbai and Uran as resting places at high tide when the water level rises in the creek.
“We are also studying the behavioral responses of birds to disorders such as MTHL construction and fishing,” said Mrugank Prabhu, a scientist at BNHS and one of the residents of his Airoli field station. At this point, however, it is too early to draw any conclusions from his team’s work, added Prabhu. When asked specifically whether the ongoing MTHL construction work would have an impact on the flamingo numbers in Sewri and Nhava, he emphasized that “the birds have not left the area despite the project”.
“They keep a safe distance from the construction site and feed there in large numbers. The disruption may be temporary, but only long-term monitoring will reveal it, ”added Rahul Khot, associate director at BNHS.
“There is a lack of historical data on the subject of flamingos and the ecology of the creek, an incredibly dynamic system. Our ecological long-term monitoring study is a showcase project for shaping the nature conservation policy of the future. We are finally producing the necessary critical data for this, ”said Khot.
The lack of a proper study is a sticking point for environmentalists. Had such a long-term monitoring study been carried out prior to the construction of the MTHL, the impact of the project would be easier to assess and mitigate. “The state was content to use these flamingos as tourist attractions, but it did not think about investing in nature conservation until it absolutely had to,” said Stalin D, director of the non-governmental organization Vanashakti.
Raise concerns
The main objection of the environmentalists to the MTHL was its direct passage through the Sewri-Mahul Wadden Sea, which provides a habitat for up to 15% of the near-threatened Lesser Flamingos (Phoeniconaias minor) in South Asia.
In its preliminary assessment, the BNHS recommended that this section be redirected, but the proposal was not accepted by the state government.
However, based on the demands of environmentalists and a recommendation from the Union’s Ministry of the Environment, in 2015 the state declared 1,690.5 hectares of the creek – in Mulund, Vikhroli, Bhandup, Kanjur and parts of the village of Mandale – a flamingo sanctuary even a 10- Annual management plan drawn up. Since MTHL cuts through a considerable part of the habitat of migratory birds in Sewri and Nhava, the nature reserve has demarcated a zone north of the MTHL, in which further development and infrastructure projects would be restricted.
However, experts also warned that the MTHL isn’t the only thing to watch. Pollution from domestic sewage, sewage from over 4,000 industrial plants lining the creek, and hot water discharges from the Tata thermal power station and the BARC nuclear research reactor cause an edge effect: rapid ecological changes between two habitats (such as land and water) that can create a range of specific conditions that allow certain species to thrive. In this case, the rapid pollution and silting in Thane Creek leads to a proliferation of food (and food) grounds and increases the number of flamingos.
“It is paradoxical that pollution helps flamingos thrive. The real question is to what extent the stream can sustain these processes before risking their survival? ”Asked Dr. Prasad Karni, a biologist and member of the Paryavaran Dakshata Mandal, a Thane-based environmental protection group.
The rapid silting up makes the stream shallower and narrower. HT reported on June 14 that a study by the State Forest Department’s mangrove cell indicated that Thane Creek has lost 30 km² of its water span since 1972, turning most of that area into fresh mudflats. These are believed to support flamingos for a while, but soon they are overgrown by mangroves that take root in the silt.
“Flamingos and migratory waders benefit from the shrinking waterways, as their population growth can be observed in the same course as the expansion of the mudflats and mangroves. This in combination with the high wastewater pollution that MMR pumps into the stream, as well as the warm water from refineries and power stations, make it a perfect food source with a nutrient-rich flora and fauna, ”said Dr. Deepak Apte, a marine biologist who ran the MTHL flamingo surveillance program as a former director of BNHS.
“In my opinion, MTHL isn’t as big a problem as these other changes in the creek. Heavy silting already promotes the growth of mangroves, which, if not controlled, exceed the space available for birds to forage. This is not good news for flamingos who prefer flat mud flats over mangrove forests, ”said Apte, calling for an ecological restoration plan to be implemented for Thane Creek.
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