CHENNAI: Decades after green revolution brought about internationally acclaimed success in increasing agriculture production, experts are studying its disastrous impact on the food chain near three bird sanctuaries in Tamil Nadu. The pesticides and insecticides that help farmers are washed away and deposited in waterbodies by oodwaters, leaving sh and birds as the non-targeted but worst-aected.
An ongoing scientic study by Salim Ali Centre for Ornithology and Natural History (SACON) in Vedanthangal, Vettankudi and Koonthanulam bird sanctuaries over the decade has conrmed heavy deposition of pesticides into the food chain. The pesticides and insecticides used in farmlands of Chengalpattu, Kancheepuram and Tirunelveli have entered the waterbodies through stormwater.
Due to this, sh-eating birds like cormorant, heron, darter, egret, pelican are showing signs of toxic poisoning like egg thinning, where eggs do not hatch. Similar deposition of organochlorines had already led to droopy heads among vultures, warn scientists studying the toxic deposition in birds and food chain. “Accumulation of chemicals in aquatic organisms is slowly deteriorating the other food chain systems. There is a need for long-term study on the birds that get aected due chemical pollution. Mortality of birds due to pesticide poisoning has become rampant,” said S Muralidharan, principal scientist, department of ecotoxicology, SACON.
“Despite the ban on many persistent pesticides, residue levels of certain pesticides in many species of birds are a cause of concern,” explained Muralidharan. However, addressing the issue is easier said than done. “There is no baseline data on pests and insects. Only if we think about addressing the pest issue for farmers can we stop them from using pesticides. The other safe option is to revert to organic farming and bring more land under cultivation,” Muralidharan opined.
“Wildlife institutes like SACON, Wildlife Institute of India, Bombay Natural Historical Society, and Centre for Cellular and Molecular Biology had conrmed pesticide poisoning by documenting the chemical contamination in more than 150 bird species in the country,” said A Kumaraguru, founder, Biodiversity Conservation Foundation (BCF), Tiruchy. Chemical deposition in ecosystem is a serious issue, which, however, goes unchecked.
BCF has already started a campaign on toxicology and birds, under which international webinars on the impact of chemicals on birds are organised for naturalists, he said. Fish, due to their position in the aquatic food chain and their nutritive value, are considered to be a better indicator of wetland contamination. They too suer from heavy chemical deposition, with DDT, methoxychlor, dieldrin, chlordane, toxaphene being some of the common chemicals found in sh and sh-eating birds, Kumaraguru said