Heat, drought, floods, cyclones. Could a bio-shield be the answer?
Cyclone Amphan, which hit West Bengal in May 2020, was the first supercyclone in the Bay of Bengal since 1999, and one of the fiercest to hit the state in 100 years. Exactly a year on, Cyclone Yaas hit.
West Bengal has always had more than its share of hydro-meteorological disasters — floods and cyclones, downpours and lightning strikes. It has the highest death toll from such events of any state in India, according to 2021 data from the Union ministry of earth sciences, with an estimated 964 deaths between April 2018 and March 2021.
Kolkata, the state’s capital, sits at sea level, along the Hooghly river, 125 km from the coast. It has been listed as one of the seven megacities in Asia most vulnerable to disaster-related mortality. It is now at risk from fiercer storms, more intense heat waves, flooding, drought, outbreaks of vector-borne diseases, distress migrations into the city, and a further dipping of land levels as groundwater levels plummet.
For centuries, the city and the state were protected by the Sunderbans, the world’s largest mangrove delta. But the Sunderbans has been losing its very dense mangrove cover, as a result of intensifying storms and rising salinity.
In one sweep, 1,600 sq km of mangrove forest were damaged by Cyclone Amphan.
While an IPCC report from 2019 states that sea level is rising by 3.6 mm every year, the Sunderbans delta is subsiding by 2.9 mm every year. “These two figures put together show that water is gobbling up land at the rate of 6.5 mm per year,” says Kalyan Rudra, river expert and chairperson of the West Bengal Pollution Control Board.
Intensifying heat waves are set to raise the risk of drought. “With rising temperatures, cases of vector-borne diseases such as malaria and dengue are also expected to rise,” says Tuhin Ghosh, director of the School of Oceanographic Studies at Jadavpur University.
Is Kolkata prepared to handle the crises? Human activity continues to eat away at carbon sinks and natural aquifers. “Unbridled development has obstructed the natural drainage system into the East Kolkata Wetlands, which act like the kidneys of the city. As groundwater levels across the city plunge, this may result in gradual subsidence of land,” Ghosh says. Meanwhile, the city’s stormwater drains, like Mumbai’s, date back a century, to colonial times.
The state’s forest department is now working to create a “bio-shield”, a sort of sea wall made up of various plant species that can absorb the impact of storms and protect coastal areas, including the Sunderbans.
“There has to be a combination of strengthening green and blue infrastructure. While green infrastructure includes urban greening and biodiversity protection for different climate anomalies, blue infrastructure refers to protecting and enriching water bodies, cascading lake systems, streams and rivers,” says Anjal Prakash, a climate scientist and co-author of the recent IPCC report. “It is important going forward for Kolkata and other cities to focus on resilience plans.”