Side effects of biotech major Monsanto's herbicide Roundup, brought to light recently, have worried environmentalists. In a test in simulated shallow ponds, the herbicide killed 98 per cent tadpoles, says a study by University of Pittsburgh ecologist Rick Relyea, published in the August 2005 issue of journal Ecological Applications.

The study also cites a dry experiment in which Roundup killed 79 per cent of young frogs and toads after just one day. "It's much deadlier than we thought,' warns Relyea. Though Monsanto specifies that the herbicide shouldn't be used near water, Relyea points out that many amphibians live in shallow puddles in fields and forests and might suffer accidental spraying. As it is, the number of amphibians has declined sharply since the 1970s. Relyea stresses that though the evidence that Roundup is contributing to the global decline does not exist, his study shows how lethal it is. Monsanto contends that the concentrations of Roundup used in the study were too high.

Another adverse effect of Roundup was revealed when California farmers recently detected that horseweed had grown resistant to the herbicide and had become a nightmare for them. University of California researchers also expressed alarm at the weed's proliferation; it reproduces fast, growing upto 3.7 metres tall, consuming nutrients.