East Kolkata Wetlands: The Natural Kidneys of our Ecosystem

Wetlands are a place or an area with a well-defined ecosystem that is flooded by water, usually natural water- freshwater or seawater or even drainage water from the cities either periodically or cyclically. The flooding results in an anoxic environment, where specially adapted plants like hydrophytes can thrive and promote the development of hydric soil as well. Wetlands are home to various species of birds and not only aquatic animals but terrestrial animals as well. The East Kolkata Wetlands, on the outskirts of the Kolkata Metropolitan Area, spread over 12,500 hectares of land comprising 254 sewage based fishing grounds, farming and agricultural lands, and settlement areas. 

The East Kolkata Wetlands treats about 900 million litres of drainage water every day, acting as an absorber basin for the large number of pollutants drained from the Kolkata Metropolitan City. Natural and man-made canals and creeks are used to bring sewage water to the wetlands making it one of the largest resource recycling ecosystems. The recycled water is used for agriculture, and pisciculture acts as a source of drinkable water for the nearby villages and settlements and also acts as the city’s flood resistance. The wetlands have saved the State government from constructing and maintaining a wastewater treatment plant. The wetland waters were brackish at one point in time because of the estuarine river Bidyadhari(distributary of Ganga and Brahmaputra delta), which earned it the name salt lakes. The local fishers turned to sweet water fishes from the saline ones in the last decade of the nineteenth century since the treated sewage treated water is sweet. Although there are both brackish and freshwater fish ponds. Vegetables and paddy are also cultivated in the lands using treated freshwater. The local farmers and fishers have adopted the complex system of the wetlands resource recovery by mastering it, thus creating sustainable development. The sewage water is treated using solar purification then natural oxidation which leads to favourable conditions for algal and plankton growth which are then fed to the fishes. Agriculture being predominant is found in 59% of the total area then followed by settlements. 

The wetlands hold a significant amount of biodiversity values, there are about 104 plant species, marsh mongoose and small Indian mongoose which are rare mammals, also palm and Indian civets and the threatened species of an Indian mud turtle. 52 endemic varieties of fishes of which 34 are threatened and some studies from soil cultures have found that there are new strains of microorganisms that have developed over time and been growing which may have commercial value other than the primary ecological value. Studies have shown that some species of liverworts and mosses which are called bryophytes play an important role to maintain the ecosystem like soil conservation, habitat modification, nutrient cycling and pollution detection and monitoring, providing shelter to various other microorganisms. They may also have pharmaceutical and chemical significance due to the presence of various flavonoids and terpenoids in them. Several aquatic plants are used as compost and manure, which are primarily used as food for fish and the purification of water. This level of biodiversity is possible due to the diverse habitats which enable a wide range of animals and plants to survive. 

The wetland system maintains a striking balance between economy and ecology, it serves as an air purifier because of the hundreds of trees in the area, carbon sequestration and flood control. The wetlands being a natural depression provides extensive water holding capacity, and the flood depletion function of the wetlands provides a natural buffer against high flows. Through aquaculture, horticulture and irrigation the wetlands serve as a resource recovery for the city of Kolkata. The wastewater gets treated by the use of a plant known as water-hyacinth and the process is known as water-hyacinth mediated phytoremediation. The traditional waste recovery practice provides subsistence opportunities for the large underprivileged population who inhabit the area. They also provide recreational avenues for the urban and peri-urban populations. In recent times, to make more money, some fishers have converted their fish farms into hotspots like boat restaurants and picnic spots. 

The wetlands are under a threat because of the developing urbanization. Although the wetlands were declared as a RAMSAR site in the year 2002, its weak administration, lack of coordination among various nodal agencies and change in quality and quantity of the sewer waste has resulted in its threat. The wastewater is the natural food for the fish has changed over the years due to changes in elements, now its more plastics, more caustic wastes from soap and leather products, deposition of heavy metals which have led to bioaccumulation of heavy metals in fish and plant species and even medical waste which has made the fishes inedible. Earlier the urban waste recycling system was a boon in disguise as it was valuable for the wastewater fed pisciculture but now it's the opposite. The native fishes are under great threat due to the increasing population of invasive exotic fish species. The then endangered marsh mongoose is under threat again due to habitat loss. The wetlands have shrunk over the years because of the use of the wetlands for non-wetlands purposes like converting large parts of the wetlands into aquaculture ponds which are deprived of vegetation and also because of the construction of the Eastern Metropolitan Bypass. The wetlands play an important role in maintaining environmental sustainability. The anthropogenic activities and ignorance of the values the wetlands hold have caused a decline in the quality of water in the wetlands. The human activities which have caused a decline in the water quality are the use of pesticides for agriculture, the use of artificial resources and adding unnecessary and hazardous effluent into the water bodies. The natural hydraulics of the wetlands have been altered over the years due to climatic changes. The increasing air pollution and land pollution have resulted in an increase in the amount of silt in the water bodies thus reducing the volume of water. The wetlands being neglected by the urban population and unwanted discharge from the industries have led to the breeding grounds for mosquitoes. The esthetic values apart from the well-known sustainability values the wetlands hold are also immense. 

To reach the East Kolkata Wetlands, you can take V1 which is a sustainable electric bus which starts from Airport Gate 1, you need to halt at Chingrighata bus stand, from there you can walk to the spot. Since it’s a massive area you would have to walk a lot, so better carry a big water bottle preferably an earthen clay water bottle which would keep the water cool. If you want to come by metro then the nearest metro station would be Saltlake Sector V, from there you could reach the spot using any mode of transport. 

As a sustainable resource, the value that the wetlands held at one time has changed its course on the way. The local communities, mainly the poorer and weaker section of the community’s livelihood depend upon the wetlands, they are nurturing the wetlands over the years. The wetlands are one of the best examples of low-cost alternatives in the Municipal Waste Management System that can certify the long term recovery of nutrients available in waste. The Kidneys of the city or the East Kolkata Wetlands need to be protected and preserved for the betterment of the city keeping in mind the sustainable development goals, the strong need to appreciate and recognize its importance and the future of sustainability it holds.