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2016-08-30

Neonicotinoid insecticides linked to long-term wild bee decline in England

Rape Bee in a rapeseed field (Photo: CC0)

New research has linked the the large-scale and long-term decline in wild bee species across England to the use of the controversial neonicotinoid pesticides. According to a study published on 16 August in the journal Nature Communications, wild bees are negatively affected by exposure to neonicotinoids on oilseed rape. “Over recent years there has been a growing body of evidence that seed-coated neonicotinoids are harmful to beneficial insects, including bees. However, most of these studies are based on short-term experiments on honeybees,” explained co-author Dr. Nick Isaac from the Centre for Ecology & Hydrology in Oxfordshire. “Our study is different because we looked at long-term trends for 62 wild bee species across all of England.” The researchers used bee population data collected by volunteers from more than 31,818 surveys across more than 4000 square kilometres of land across England between 1994 and 2011. This time period covers the years before and after the introduction of wide-scale commercial use of neonicotinoid seed treatments on oilseed rape in 2002. The scientists also analysed data on the area planted with oilseed rape over this 18-year period and the proportion of neonicotinoid seed treatment applied to this crop before planting. The scientists found evidence suggesting that the decline in wild bee populations was, on average, three times stronger among species that habitually forage on oilseed rape, for example the buff-tailed bumblebee (Bombus terrestris), than among species that regularly forage on a range of floral resources. “As a flowering crop, oilseed rape is beneficial for pollinating insects. This benefit however, appears to be more than nullified by the effect of neonicotinoid seed treatment on a range of wild bee species, “ said lead author Dr Ben Woodcock. Although the authors admit that neonicotinoids may not be considered in isolation of other pressures such as habitat loss, pathogens, climate change and other insecticides, they call attention to the large exposure risk to pollinators: According to the study, neonicotinoids comprised 80% of the worldwide insecticide seed treatment market in 2008 or 24% of the total insecticide market. In 2013, the European Union imposed a temporary ban on the use of three neonicotinoids – clothianidin, imidacloprid and thiamethoxam to protect bees. This moratorium is currently being reviewed. The European Food Safety Authority (EFSA) is expected to complete its new assessments of the risks to bees posed by three neonicotinoid pesticides by January 2017. However, the British government has already temporarily lifted the ban on neonicotinoids last year, allowing “emergency rules” for the use of the insecticide in certain parts of the UK. (ab)

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