Bee-Killing Pesticides Linked to Lower Farmland Bird Population

Pesticides don't just harm bees, but also reduce population of farmland birds, a new study reveals.

Researchers at the Radboud University in Nijmegen and the Dutch Centre for Field Ornithology and Birdlife Netherlands (SOVON) said that use of a certain class of pesticides in farms has reduced bird populations in the area, National Geographic reported.

The pesticides implicated in the current study are called neonicotinoid pesticides, which are a class of pesticides that are taken up by the plant and are present in the nectar.

Previous research has found that it causes population decline in bumblebee colonies. Related study stated that honeybees were being affected by the pesticide.

EU had imposed a two-year ban on some of the neonicotinoids in Europe starting April, 2013.

A recent study from UK also showed that the pesticides that persist in the environment harm soil organisms, birds and fish.

For the study, researchers compared long-term data sets for insect-eating bird populations and chemical concentration of surface water. They found that high concentration of imidacloprid - a common neonicotinoid pesticide - was linked to a reduction in bird numbers by 3.5 percent per year, National Geographic reported.

Researchers accounted for other factors such as increase in farming activities in the region, but found that only imidacloprid could explain why the farmlands were witnessing a "Silent Spring."

"It is very surprising and very disturbing," said Hans de Kroon, an ecologist at Radboud University, in the Netherlands, according to the Guardian.

Around 20 nanograms of neonicotinoid per litre of water led to a 30 percent decline in bird population over ten years. Researchers found that in some areas, the concentration was up to 50 times higher. "That is why it is so disturbing - there is an incredible amount of imidacloprid in the water," he told The Guardian. "And it is not likely these effects will be restricted to birds."

Rachel Carson had talked about insect-killing chemicals and their effects on the environment in her book Silent Spring. "I think there is a parallel, of course," said Ruud Foppen, an ornithologist at SOVON and a co-author of the paper, National Geographic reported.

Carson warned against the overuse of organophosphates like DDT. In the current study, researchers found that another class of pesticides - neonicotinoids - has become a threat to biodiversity.

The study is published in the journal Nature.