WIKIMEDIA, ROSENDAHLTreatment of oilseed rape, a major flowering crop grown in England, with neonicotinoid pesticides is correlated with population declines of wild bees, according to a study published today (August 16) in Nature Communications, in which researchers examined links between the area of chemical-treated crops and populations of 62 wild bee species across parts of the United Kingdom for 18 years.
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Woodcock says the work, which expands on previous short-term studies, shows there are “population level changes” across the “wider community of wild bees that you find in the UK”.
“It’s not a simple case that pesticides are causing declines”, he said. This is because the alternatives may also have negative effects on wildlife.
It found an average population decline across all species exposed to treated oilseed rape of 7% between 2002 and 2011, after the pesticide came into wide-scale commercial use.
Of the 100 crop species that provide 90 per cent of the world’s food, over 70 are pollinated by bees.
They looked at bee populations between 1994 and 2011.
A key innovation was the commercial licensing of neonicotinoid insecticides for the crop in the United Kingdom in 2002. To get this bees need to visit lots of pesticide-free plants – endless fields of oil seed rape are failing to provide this’. On average, the effect on their population was three times as severe as the effect on species that don’t forage on rapeseed.
“What we’ve been able to do here is look over a much longer time period and look at over 60 species in the United Kingdom, so it’s giving a much more comprehensive idea of the longer term potential negative impacts of this pesticide”, he told The Scientist.
“Neonicotinoids are harmful, we can be very confident about that and our mean correlation is three times more negative for foragers than for non-foragers”. “From a correlative perspective, there’s an underlying mechanism that’s driving [the decline] and.it’s likely to be exposure to neonicotinoids applied to the oilseed rape crop”, said study coauthor Ben Woodcock.
“The worst affected species declined by 30 per cent”, says Nicholas Isaac, of the CEH. Neonicotinoids are particularly toxic to bees because they are systemic pesticides. “If the government genuinely wants to safeguard Britain’s bees, it must keep the ban on neonicotinoid pesticides regardless of what happens with Brexit”, said Friends of the Earth nature campaigner Paul de Zylva.
The manufacturers of the chemicals agree that it is an interesting statistical study, but they argue that intensive farming and not just a single insecticide might be the real cause of the decline.
By 2011, the proportion of United Kingdom oilseed rape seeds treated with them was 83 percent, according to the researchers leading this latest study.
Other scientists, though, believe that the new study is some of the strongest data yet for the impact of these substances over the long term. “This benefit however, appears to be more than nullified by the effect of neonicotinoid seed treatment”.
The European Food Safety Authority is now conducting a review of the scientific evidence about neonicotinoids. “Banning pesticides altogether is probably hard, I’m afraid”, and restricting use of one pesticide could potentially lead to the introduction of a replacement pesticide with its own set of potential problems, he said. This new work is likely to be part of that review, along with another, major field study due out in the Autumn.
But the National Farmers’ Union disputed the findings.
‘Wild bees have undergone global declines that have been linked to habitat loss and fragmentation, pathogens, climate change and other insecticides’.
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The scientists involved in the wild bee study caution against “simplistic solutions” to the problems of pollinators.
