By Lucy Gibson
Vembanad Lake is India’s longest freshwater lake. With a lake area covering approximately 250 km2 and with a catchment area covering 14,000 km2, Vembanad Lake, located within the state of Kerala, is included in the list of wetlands of international importance, as defined by the Ramsar Convention for the conservation and sustainable utilisation of wetlands.
Home to more than 20,000 waterfowls, such as spot billed pelican and oriental darter, and Kumarakom Bird Sanctuary, located on the eastern banks, Vembanad Lake is an ornithologist’s paradise. Set within lush woodland, this site is also a favourite to migratory birds (such as the Siberian stork, flycatchers, and larks) who flock in their thousands from miles away. Flying along the Central Asian Flyway, migratory birds travel from their northern breeding grounds, some as far away as Siberia, to their wintering grounds in the Indian subcontinent.
Additionally, over 1.6 million people live on the banks of the Vembanad Lake and are directly or indirectly dependent on it for their livelihoods. Major livelihood activities of the people living on the shores include agriculture, fishing, tourism, inland navigation, and coir retting.
However, as Vembanad Lake is fed by seven major rivers plus many streams and canals, all of which flow through densely populated urban areas (for example, the major city of Kochi, 12 municipal towns, and approximately 100 villages) the possibility of occurrence of pollutants and microplastics in the lake sediment is high.
Plastics wastes are of significant environmental concern due to their longevity and worldwide distribution. India is one of the major plastic consumers in the world, generating approximately 5.6million tonnes of plastic waste annually. Vembanad Lake is one of the most polluted water bodies in India with microplastics (<5mm in size) ubiquitous and abundant in sediment samples from across this water body in a recent study.
Microplastic contamination poses a grave risk to aquatic fauna. LITTERBASE, a database which presents the distribution of litter across the world, and its interaction with wildlife, notes that ingestion is the most frequently observed interaction, followed by entanglement. When microplastics are ingested by the benthic fauna and zooplankton, this can trigger the contamination of the whole food web.
Additionally, a study revealed by the Kerala State Pollution Control Board highlighted the concerning presence of heavy metals and pesticides in Vembanad Lake, such as zinc, nickel, and copper, as well as benzyl benzoate and benzene propanoic acid which have application in the pharmaceutical industry. This also poses a major health hazard to ecosystems and to humans via trophic transfer.
Vembanad Lake holds a rich population of black clam and other clam species. Annually, 31,650 tonnes of clam are fished from the lake for local consumption, as well as prawns, crabs, and fish which are staples proteins for local residents. Potential microplastic and heavy metal contamination, therefore, becomes critically important, posing threat to the local fauna and the health of local residents through ingesting plastics and toxins.
As a result of houseboat tourism and sewage discharge, the water quality has declined with low dissolved oxygen levels and high biochemical oxygen levels. This has affected aquatic life: as per the latest fish survey report, Vembanad Lake only has 98 fish varieties, when just a decade ago, there were 150 species.
Polluted by plastic, various organic and household waste, industrial activities and anthropogenic activities like land reclamation, Vembanad Lake’s incredible environment is at risk.
Concerted efforts in improving and monitoring waste management programs, emphasising the three ‘R’ principle of reduce, reuse, and recycle for plastic management, may reduce the abundance of plastics and microplastics in the lake. Additionally, the findings of Yunus et al.’s study (2020) on the effects of COVID-19 lockdown on surface water quality showed that the pollutant level of Vembanad Lake decreased considerably when industries and boating were suspended. They argue that now is the time to act, based on the Ramsar Convention framework, to reduce the environmental damage to the Vembanad Lake ecosystem.