The research, led by the Centre for Ecology & Hydrology using data provided by Fera Science and the Bees, Wasps and Ants Recording Society, examined changes in the occurrence of 62 wild bee species with oilseed rape cropping patterns across England between 1994 and 2011 – the time-period spanning the introduction of wide-scale commercial use of neonicotinoids.
Neonicotinoids are a class of neuro-active insecticides that are similar to nicotine. They include imidacloprid – the most widely used insecticide in the world.
The decline reported in the latest research was, on average, three times greater among species that regularly fed on the crop, such as the buff-tailed bumblebee.
According to the researchers, the data suggested that neonicotinoid use correlated with wild bee biodiversity losses at a national scale and had implications for the conservation of bee communities in intensively farmed landscapes.
‘Beneficial to pollinating insects’
Lead author Dr Ben Woodcock said: “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.
“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.”
Professor Lin Field from Rothamsted Research said: “The paper addresses an extremely complex problem, since we know that many bee species were already in decline prior to the introduction of neonicotinoid seed treatments in oilseed rape.
“The findings, therefore, need to be considered alongside other published studies and further evidence as it becomes available, rather than in isolation.”
National Farmers Union bee health specialist Dr Chris Hartfield said the study was an “interesting” addition to the existing evidence.
“It does not show that neonicotinoids are causing widespread declines in pollinator populations and it certainly does not show that neonicotinoid use has caused any extinction of bees in England,” he said.
While this study supports the EU moratorium on some uses of neonicotinoids, there are still major gaps in our knowledge, he added.