“Neonicotinoids: new warning on pesticide harm to bees,” and “No sign of damage to honeybees from neonics, review shows.” These are two very different, quite conflicting headlines that are referring to the same recently published study. More than anything, this actually highlights one of the main conclusions drawn: there isn’t enough evidence yet to reach a consensus on the effects of exposure to these pesticides on insect pollinator populations.
The focus of this analysis, led by researchers at Oxford University, was a type of insecticide called neonicotinoids, or neonics. Introduced about 20 years ago, once applied these pesticides spread throughout the plant and fatally attack the nervous system of insect pests that consume them and thus help protect the crop from damage. But they also make their way into nectar and pollen where they can subsequently be consumed by pollinators like bees that also forage in the same area.
The issue is not whether bees are getting exposed to these chemicals, though; that’s well known. The controversy stems from whether or not exposure harms bees. Studies have shown that bees exposed to below lethal doses of these pesticides exhibit impairments in learning, feeding, navigating and foraging; collectively these can lead to colony failure. That said, it has been argued that the levels used in some studies are far higher than would be encountered in the field.
Another problem is that scientists have yet to agree on whether these individual effects damage the population as a whole and contribute to the declining populations that we are currently witnessing. One study widely cited, conducted in Sweden, found that neonics are indeed capable of reducing bumblebee populations, but the same was not found for honeybees.
Despite a lack of consensus, a two-year moratorium was put in place in the EU back in 2013 because of the potential risks they pose, a decision that was opposed by many due to the potential economic impacts. But some farmers insisted there weren’t any suitable alternatives and therefore managed to get round the ban by applying for 120-day exemptions.
A review of the available data was therefore desperately needed so that policymakers can base their decision of whether to continue the ban or not on the best available evidence. That’s why the U.K. government’s chief scientific adviser Professor Sir Mark Walport requested the present analysis be conducted, published in Proceedings of the Royal Society B, which looked at hundreds of papers on neonics and insect pollinators.
While the authors don’t dispute that exposure to levels of those representative found in the field imparts negative effects on individual bees, whether or not this goes on to affect populations as a whole is still unclear. Lead author Charles Godfray pointed out at a news briefing that it’s possible natural buffering experienced in wild populations can compensate for the losses of some individuals, meaning declines can be avoided, the Guardian reports.
“The evidence so far points to a lack of effect on honeybee colonies from neonicotinoids,” he concluded, Farmers Weekly reports.
That’s not quite the definitive conclusion people are seeking; evidently, more data from the field is needed, but hopefully some recently conducted studies will help scientists reach a much-needed agreement on the matter.