Is this chemical the reason bees are disappearing?

Scientists analysed data on bees collated in Yorkshire and found species exposed to crops treated with neonicotinoids saw a drop in numbers of up to 30 per cent between 2002 and 2011.

The pesticide is already under a two-year ban by the EU amid concerns over its impact on bees, such as damaging their ability to forage and navigate, and colony growth.

Dr Nick Isaac, who co-authored the paper, said the damaging effects of the pesticide reported in small-scale studies had been replicated.

“The negative effects that have been reported previously, they do scale up,” he said. “They scale up to long-term, large-scale multi-species impacts that are harmful.”

The research, led by the Centre for Ecology and Hydrology (CEH), looked at the patterns of 62 species of wild bees across England between 1994 and 2011.

It examined data provided by York-based Fera Science and the Bees, Wasps and Ants Recording Scheme, analysing 31,818 individual surveys over more than 4,000 sq km of land.

The research found, of those exposed, there was an average decline in population numbers by seven per cent between 2002 and 2011, when the pesticide was in wide-scale use. Among the 34 species that feed on oilseed rape, there was a 10 per cent decline, while five of the species studied declined by 20 per cent or more.

“As a flowering crop, oilseed rape is beneficial for pollinating insects,” said Dr Ben Woodcock, the lead author of the paper published in Nature Communications. “This benefit however, appears to be more than nullified by the effect of neonicotinoid seed treatment on a range of wild bee species.”

Researchers said the study showed a decline in the number of populations of bees, not a decline in the number of bees overall. Among the worst-hit was the lime-loving furrow bee, which saw a 23 per cent decline, while Hawthorn mining bee populations fell by 18 per cent.

Neonicotinoids are applied to the seed prior to planting and can be transported to all tissues of a crop, meaning they can be ingested by pollinators which feed on the nectar. The moratorium on the pesticide could be lifted following a review by the European Food Standards (FSA), which is due to be completed in January and will be informed in part by the new paper.

But Dr Woodcock warned neonicotinoids should be considered as a “contributory factor” to decline in the number of populations of wild bee and said a “complex array of drivers” including habitat, climate change and disease were also important.

“It’s not a simple case that pesticides are causing declines,” he added. “It’s likely that there’s a whole series of interacting factors and while people like a one-shot solution, it’s probably not the case in most situations.”