By Damian Carrington | Guardian.co.uk
New research suggests the chemicals are playing a significant and previously unknown role in the global decline of amphibians
Widely used pesticides can kill frogs within an hour, new research has revealed, suggesting the chemicals are playing a significant and previously unknown role in the catastrophic global decline of amphibians.
The scientists behind the study said it was both "astonishing" and "alarming" that common pesticides could be so toxic at the doses approved by regulatory authorities, adding to growing criticism of how pesticides are tested.
"You would not think products registered on the market would have such a toxic effect," said Carsten BrŁhl, at the University of Koblenz-Landau in Germany. "It is the simplest effect you can think of: you spray the amphibian with the pesticide and it is dead. That should translate into a dramatic effect on populations."
Trenton Garner, an ecologist at the Zoological Society of London, said: "This is a valuable addition to the substantial body of literature detailing how existing standards for the use of agricultural pesticides, herbicides and fertilisers are inadequate for the protection of biodiversity."
Amphibians are the best example of the great extinction of species currently under way, as they are the most threatened and rapidly declining vertebrate group. More than a third of all amphibians are included in the IUCN "red list" of endangered species, with loss of habitat, climate change and disease posing the biggest threats.
BrŁhl had previously studied how easily frogs can absorb pesticides through their permeable skins, which they can breathe through when underwater. But pesticides are not required to be tested on amphibians, said BrŁhl: "We could only find one study for one pesticide that was using an exposure likely to occur on farmland."
His team chose widely used fungicides, herbicides and insecticides. The most striking results were for a fungicide called pyraclostrobin, sold as the product Headline by the manufacturer BASF and used on 90 different crops across the world. It killed all the common European frogs used as test animals within an hour when applied at the rate recommended on the label. Other fungicides, herbicides and insecticides also showed acute toxicity, even when applied at just 10% of the label rate, with the insecticide dimethoate, for example, killing 40% of animals within a week.
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