The elderly Bengali fish farmer Tapan Kumar Mondal, who spent his life in the wetlands east of Calcutta, worries about the urban pressures exerted today on this vital ecosystem for the Indian megalopolis, nicknamed: "the kidneys of Calcutta ".
"We are gradually destroying the environment," laments the 71-year-old former fish farmer to AFP, "the pressure exerted by the population, now more numerous than before, harms the natural environment".
For more than a century, these wetlands, which extend over 125 km2, have served as a "biological treatment plant" for the Indian agglomeration of 14 million inhabitants, thanks to the practice of fish farming.
"This is a unique case, because the city's wastewater is naturally treated there," K. Balamurugan, head of the environment department of the state of West Bengal (east), told AFP.
"That's why they're called Calcutta Kidneys," he adds.
Every day an ingenious system of canals conveys approximately 60% of the wastewater produced by the capital of West Bengal, or 910 million liters, to the basins of the wetlands.
"As the water level does not exceed 1.50 m, the sunlight combined with the wastewater causes an explosion of plankton in fifteen or twenty days", explains Mr. Balamurugan.
This rich and abundant plankton feeds the fish ponds operated by fish farms, which breed carp and tilapia in particular.
The effluents from these bodies of water, covered with water hyacinth, are used to irrigate the rice fields and the organic waste is used as fertilizer for vegetable production.
The practice of fish farming thus not only makes it possible to treat the city's wastewater for free, but also to supply it with some 150 tonnes of vegetables per day and 10,500 tonnes of fish per year at a lower cost.
In this region of the Ganges delta, bordered by the Indian Ocean and threatened by rising waters, wetlands play a crucial role in flood control.
"Kolkata has never faced a problem of flooding as the wetlands act like a sponge by absorbing excess rainwater" during the monsoons, adds Mr Balamurugan.
These wetlands are on the list of the intergovernmental Ramsar Convention, which is concerned about "urban expansion" threatening this mini-biosphere.
According to Dhruba Das Gupta, a researcher at SCOPE, a non-governmental organization for research on ecosystems, these wetlands are "much more than the kidneys of Calcutta (...) they represent its lifeline".
They help to regulate local climatic conditions, in particular rainfall and temperature, with favorable effects for agriculture and the conservation of natural ecosystems, including the wetlands themselves.
"Wetlands must be preserved because of the coolness provided by the bodies of water present," Das Gupta told AFP. "It is a fundamental element in stabilizing the climate of the city, preventing warming".
A virtuous circle is at work there and, according to the expert who has been concerned with it for 25 years, fish farmers are the main guarantors.
Also, Ms. Das Gupta is currently seeking to fund a study to determine the precise area of fish ponds that are still "fully active", the number of people who work there all year round and the yield of fish production.
Thanks to fish farming, the Kolkata Municipality (KMC) saves the equivalent of $64.4 million per year in the cost of treating its wastewater, according to a study by the University of Kolkata published in 2017.
This makes Calcutta, in the words of the first defender of its wetlands Dhrubajyoti Ghosh, an "ecologically subsidized city".
"The wetlands have shrunk", adds the specialist, "but the most important thing is the total number of hectares of water bodies remaining".
Production levels have changed, the population has increased, buildings are encroaching on production spaces while land prices are soaring.
"The land is being taken away from people," said Sujit Mondal, a 41-year-old fish farmer.
But K. Balamurugan argues that since 95% of wetlands are privately owned, the authorities are only entitled to prevent bodies of water from being filled in and uncontrolled construction.
“Private property is on paper but in practice there are many land issues,” replies Das Gupta.
"Panchayats, rural communities, are very corrupt," she continues, "residents often accuse them of granting unofficial building permits to developers for money."
Only the Wetland Management Authority (EKW Management Authority) is empowered to issue building permits.
Henchmen even go so far as to steal fish from the ponds in the middle of the night, to ruin the fish farmers and push them to leave.
"They put pressure on fish farmers to give up their livelihood," she adds, "and then they take control of the land."
18/07/2023 10:54:32 Calcutta (Inde) (AFP) © 2023 AFP
