Scientists say the industry-funded work confirms that neonicotinoids are harmful, but manufacturers question its conclusions.

Nature Journal

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The largest study so far on the fraught question of whether neonicotinoid pesticides harm bees is providing new ammunition for those who argue against the use of the controversial chemicals.

The large-scale field study found that overall, exposure to neonicotinoids harms bee populations. In particular, the pesticides reduce honeybees’ ability to survive their winter hibernation, say researchers.

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“We’re showing significant negative effects at critical life-cycle stages, which is a cause for concern.”

-Dr. Richard Pywell, who studies sustainable land management at the Centre for Ecology and Hydrology near Wallingford, UK, and is co-author of a paper resulting from the experiment

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…the work was mainly funded by two major neonicotinoid makers, Bayer CropScience and Syngenta. The [chemical corporations] question the scientists’ conclusions and defend the pesticides, which are already banned or restricted in several countries. [Both corporations] have responded by questioning the authors’ data analysis and conclusions.

[However,] the researchers who did the work say they were totally independent…and stand by the paper, which was peer reviewed, [noting] that the entire experiment was conducted under the scrutiny of a independent advisory board that included a statistician.

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Backstory

In recent years, concern has grown among scientists and policymakers that neonicotinoids harm bees; the pesticides are often applied to seeds before they are sown, and can later be found in pollen.

But laboratory studies investigating the effects on bee health and behavior have sometimes been criticized for giving the bees bigger doses of the chemicals than they would experience outdoors. And previous field trials have produced inconsistent results, for example finding harm to wild bees but not to honeybees.

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The New Study

To try to settle some of the outstanding questions, a team led by the Centre for Ecology and Hydrology undertook the biggest ever study of its kind, funded with US$3 million from Bayer CropScience and Syngenta, and another £400,000 (US$520,000) from the institution itself. They distributed three bee species — honeybees (Apis mellifera) and two wild varieties, bumblebees (Bombus terrestris) and solitary bees (Osmia bicornis) — across 33 field sites in the United Kingdom, Germany and Hungary growing oilseed rape. Some were placed near crops protected with neonicotinoids, and others in fields where no neonicotinoids were used.

Although the study found that neonicotinoids have an overall negative effect on bees, the results aren’t completely clear-cut: the pesticides seemed to harm bees at the UK and Hungarian sites, but apparently had a positive effect on honeybees in Germany. [The researchers] note that the German effects were “short lived”, and the reason for them is unclear.

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“The study is “well designed, well replicated, well funded — ironically by industry who won’t be best pleased. But the results tally with what has gone before.

“It’s reached a point where it’s just not plausible to keep denying these things harm bees in realistic studies.  I’d say it’s the final nail in the coffin.”

-Dave Goulson, a bee researcher at the University of Sussex in Brighton, UK

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Source: doi:10.1038/nature.2017.22229

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