RESEARCHERS in the UK have linked the use of neonicotinoid pesticides to the long-term decline in wild bee populations.
Previous studies have shown a link between acute exposure to neonicotinoids and honeybee or commercial bee species deaths, but Ben Woodcock and his team at the Centre for Ecology & Hydrology looked at long-term exposure in 62 wild bee species. They used data gathered by agricultural research company Fera Science, and the Bees, Wasps and Ants Recording Scheme, covering oilseed rape cropping patterns and bee species populations from 1994–2011. This is when wide-scale commercial use of neonicotinoid pesticides began.
Oilseed rape seeds are coated in neonicotinoid pesticides before sowing. This kills soil pests that would otherwise damage the seeds and seedlings, but also spreads through the plant as it grows, including into the nectar and pollen collected by bees.
Woodcock found that the population decline was three times greater amongst bee species that fed almost exclusively on oilseed rape, compared to those which forage more widely, suggesting that the decline is linked to oilseed rape. For five species, including the spined mason bee (Osmia spinulosa) and the furrow bee (Lasioglossum fulvicorne), local population extinctions increased by 20%.
Woodcock said that the benefits of oilseed rape for pollinating insects appear to be “more than nullified” by the effects of neonicotinoid seed treatments.
He added: “Although we find evidence to show that neonicotinoid use is a contributory factor leading to wild bee species population decline, it is unlikely that they are acting in isolation of other environmental pressures. Wild bees have undergone global declines that have been linked to habitat loss and fragmentation, pathogens, climate change and other insecticides.”
Neonicotinoids were banned by the EU for two years in 2013 to allow for further trials to determine their effects on bees but the ban was challenged by makers including BASF and industry groups like the National Farmers’ Union. The ban was overturned in the UK last year before it expired. The European Food Standards Authority is expected to complete a review of the dangers posed by neonicotinoids to bees by January 2017.
Nature Communications DOI: 10.1038/NCOMMS12459
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