Periyakulam: What are the ecological consequences of de-silting Periyakulam? Experts do some plain talking

Zoology teacher R. Selvi remembers the 320-acre Periyakulam filled to the brim. She, along with her students from Kadri Mills School have spotted hundreds of pelicans, painted storks, coots and darters there. “Once the public take up the responsibility and stop polluting the water, it will attract a lot of winged visitors” she hopes.

But there are a few questions the eco-conservationists in the city are asking. “Once de-stilted, how are we going to stop water pollution?” They say a de-silting should be in line with the ecosystem restoration plan. A wetland restoration should take into account the ecosystem, the plants, animals and birds, and the livelihood of people it supports. Hundreds of people in the immediate surroundings depend on the wetland for their survival. Local community should be actively involved to bring in a sense of ownership.

They also feel that digging and removing soil to create a mere storage capacity for water is not the right way to go about it. “Options such as a pollutant trap (which filters out pollutants) can be considered. As far as the bird life is concerned, it’s a misconception that more birds visit when the tanks are full. It’s unscientific to have islands and to nurture fruiting trees there. What we need are ‘roosting’ trees. When implemented scientifically, the goodwill initiative can go a long way to improve the groundwater level, bio-diversity, bird life, and the livelihood of people. What we need is a scientific plan,” emphasises an environmentalist from SACON.

S. Mohammed Ali, founder of Natural History Trust and author of books on wildlife, says the initiative will help improve water storage capacity of the tank and irrigation. However, it may not improve bird life.

Wetland birds

“De-silting brings habitat change to the wetlands that may keep the birds away. Zooplanktons and microorganisms thrive on silts which are food for swamp birds and waders. The common sandpiper (Kosu Ullaan) controls mosquito menace as it feeds on mosquito larvae and mosquitoes. It’s a big mistake to build islands for birds. Birds visit tanks, lakes, or puddles, and when there is change in the water level, the birds abandon the wetland. When birds select a wetland and visit regularly, we can conserve and declare it as a sanctuary, and cannot create a man-made one. What we need to do is remove encroachments from the surroundings. And, we don’t have to plant any extra trees.”

R. Mohammed Saleem of the Environment Conservation Group says a water treatment plant is the solution to stop polluted water form entering the tank. “Once the polluted water enters the tank, it seeps into the groundwater, and the pollutants enter the bore well water and drinking water at our homes.”

About the islands at the tank, Saleem says, “The islands will serve as a safe haven for birds, especially from the menace of stray dogs and also from any form of encroachments. We should plant native trees here. Banyan trees are attractive to birds for their fruits and nesting branches. So is Acacia. We can also have artificial nest boxes on the trees to attract more birds.”

He says the birds that visit the wetlands are waders that require shallow waters.

“When the water level is too deep, it discourages wader birds such as the black-winged stilts, sandpipers to name a few. Even the migratory birds such as painted storks prefer shallow waters. While de-silting, different levels of the tank have to be maintained to attract the birds. Some areas can be deep while others can be left shallow or even un de-silted.”

De-silting exercise helps in flood mitigation. “People are aware of the climate change. In the case of a heavy rain or a flood, there is now enough capacity in the tank to accommodate more water. To enjoy the benefits of the de-silting what we need is a water treatment plant. And the black soil has so many life forms which will revive once it rains.”

“We are doing one step at a time,” says R. Raveendran of Residents Awareness Association of Coimbatore, who spearheaded the de-silting exercise.

“Setting up a sewage treatment plant requires funds to the tune of Rs. One crore. We have already received Rs. 50 lakhs from the MP fund. We are in talks with the Coimbatore Corporation who have agreed to provide free electricity connection to run it. We have to identify the land and find a right contractor to install the treatment plant. We also want to go in for a three-year Annual Maintenance Contract to ensure proper functioning of the plant.”

About the birding activity, Reveendran says, “We have de-silted 100 acres with variations in the depth at the edges to encourage the birds. Also, there is another 200 acres that is still left untouched.”

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