Consensus builds among scientists though review of evidence also finds there is not enough data on whether pesticide causes population decline

There is a strong scientific consensus that bees are exposed to neonicotinoid pesticides in fields and suffer harm from the doses received, according to a new analysis of the all the scientific evidence to date.



But almost no data exists so far on whether this harm ultimately leads to falls in overall bee populations, the scientists found. They said one “gold standard” field study from Sweden had shown that the insecticides, the most widely used in the world, do significantly damage bumblebee populations. But it found no effect for honeybees, although the study design meant it could only rule out losses greater than 20%.

Bees and other pollinators are vital for many food crops but have been declining for decades due to habitat loss, pesticide use and disease. In 2013, the EU banned the use of three neonicotinoids on flowering crops for two years due to the risk they posed to bees. The UK government opposed the EU ban.

The European Food Safety Agency is now assessing the evidence for a continuation of the ban and a large-scale field trial in the UK, Germany and Hungary has been completed, with the results due in coming months.



The new work, published in the Proceedings of the Royal Society B, was requested by the UK government’s chief scientific adviser, Professor Sir Mark Walport.

“There is a pretty good consensus that pollinators foraging in agricultural landscapes, where neonicotinoids are used, will get exposed,” said Prof Charles Godfray, an entomologist at Oxford University who led the new analysis. He said pollinators were not just exposed via crops but also via wild flowers that had picked up pesticides from the soil.

“There is [also] a pretty strong consensus that, at the levels they are likely to encounter in the field, there will be some effects, possibly on their longevity or their foraging,” said Godfray. “That is pretty much established.”

But Godfray said that pollinator populations might be able to compensate for the premature deaths of individuals, so that the overall number did not decline over time. “The really big and difficult question we need to know is, are these sub-lethal effects compensated for by the buffering one gets in natural populations or are they forcing down populations of pollinators?”

Godfray said the EU ban in 2013 had been a “political judgment”, based on the evidence available at that time. “There is nothing wrong with judgment calls,” he said. “Politicians need to make judgment calls.”

He said the lack of definitive answers was frustrating: “It is frustrating to all of us in the field and especially for policymakers.” But he said the experiments that could provide strong evidence were large, expensive and time-consuming field studies. “That is the nature of the beast.”

The government, NGOs, pesticide makers and other scientists all saw and commented on the analysis before its publication.