” The decline of England’s wild bees has been linked for the first time to the use of controversial neonicotinoid pesticides on oilseed rape farms.
Neonicotinoids are applied to the seed prior to planting and can be transported to all tissues of a crop, meaning creatures that feed on the nectar will ingest them.
The various effects such pesticides might have on bees have been documented before, but there was no strong evidence linking them to long-term losses of wild bee species.
Decline of wild bee species in England linked to pesticide use, newscientist, 16 August 2016.
Now, Ben Woodcock at the Centre for Ecology and Hydrology (CEH) in Oxfordshire, UK, and his colleagues have studied data on 62 species collected by volunteers from more than 31,818 surveys across more than 4000 square kilometres of land.
They looked at bee populations between 1994 and 2011. In England, farmers first started using neonicotinoids on oilseed rape in 2002.
Controversial insecticides linked to wild bee declines, nature, 16 August 2016.
They found the average decline in populations across all bee species was 7 per cent since 2002. Some species, such the Bronze Furrow bee and the Spined Mason bee declined by 20 per cent or more. ”
Wild bee declines have been ascribed in part to neonicotinoid insecticides.
Impacts of neonicotinoid use on long-term population changes in wild bees in England, nature, 16 August 2016.
While short-term laboratory studies on commercially bred species (principally honeybees and bumblebees) have identified sub-lethal effects, there is no strong evidence linking these insecticides to losses of the majority of wild bee species. We relate 18 years of UK national wild bee distribution data for 62 species to amounts of neonicotinoid use in oilseed rape.
Using a multi-species dynamic Bayesian occupancy analysis, we find evidence of increased population extinction rates in response to neonicotinoid seed treatment use on oilseed rape. Species foraging on oilseed rape benefit from the cover of this crop, but were on average three times more negatively affected by exposure to neonicotinoids than non-crop foragers.
Our results suggest that sub-lethal effects of neonicotinoids could scale up to cause losses of bee biodiversity. Restrictions on neonicotinoid use may reduce population declines.