Battling the invasion of Vellayani Lake by invasive plant species

S.R. Praveen, THIRUVANANTHAPURAM
The Hindu, January 13, 2019 

When dancer Daksha Sheth came back to her home in Vellayani in October last year, after being away for a couple of months, she could not believe her eyes. The crystal clear water of Vellayani Lake near her home was nowhere to be seen. All she could see was a carpet of green water weeds, interspersed with purple plants.
Though invasive species has been a problem at Vellayani Lake for some years, the pace of this takeover was something new. Around the same time, Dave Ojay, a Kenyan student at the Kanthari International Institute for Social Change situated at the lake bank also talked about the problem at the institute.

Mobilising people

“Dave was involved with a movement to save Lake Victoria back home in Kenya. He found the same problem in Vellayani. He told us that the lake will be dead if we don’t do something now. He initiated a movement, gathered people and started cleaning the lake. Since then, we have been trying to mobilise people and have cleaned the lake at least every weekend,” says T.Ajith Kumar, Administration Manager at Kanthari.

New species

While water hyacinth has been a major problem for years, new exotic species like the purple coloured Cabomba caroliniana began spreading over the past decade.
According to a preliminary study conducted by the Department of Environment and Climate Change recently, other invasive species that have been noticed are Eichhornia Crassipes, Limnocharis Flava and Salvinia Molesta.
The purple-coloured Cabomba, which has spread considerably in recent months, is a native of North and South America.
It obstructs the free flow of water, gradually leading to stagnation and drying up of the lake.

Drinking water source

Vellayani Lake, the second largest freshwater lake in the State, is the source of drinking water for Kalliyoor and Venganoor grama panchayats.
“With silting on the lake bed and the constant pumping of water, the depth has reduced considerably. The shallow water allows these weeds to take root easily. A group of students have been helping us out in cleaning parts of the lake,” says Ms.Sheth.
Abhijith Nair, a young engineer, who has been part of the cleaning activities says that he has not seen such a rapid takeover by invasive plants all his life.
According to John C. Mathew, Environment Programme Manager, Department of Environment and Climate Change, the fine clay sediment and the nutrients from the agricultural fields nearby has led to the sudden spread of the invasive species. “Species like Cabomba, which were introduced to most of our wetlands from aquariums in recent years, spread quite rapidly.
“The only way to fight this is to manually uproot these plants,” he says

Action plan

The Wetland Authority has prepared a Management Action plan for these wetlands. The process for notifying them as per the Wetland Conservation and Management Rule of 2017 is currently on.
Once that is done, we can take conservation activities, for which we will get 50% Central funding.”