New study helps explain bee die-offs
Researchers with the UK’s Centre for Ecology and Hydrology have released a new study linking neonicotinoid pesticides with a long-term decline of wild bee species.
The study, published in the journal Nature Communications, analyzed changes in the population of 62 wild bee species, comparing them with patters of oilseed rape crops between 1994 and 2011, as the use of commercial use of neonicotinoids became widespread.
The findings suggest that systemic pesticides contributed to a “large-scale and long-term decline” in wild bee species distributions and communities. Species that regularly forage on treated rape fields declined, on average, three times as much as species that feed on a wider variety of plants, showing that oilseed rape is a principle mechanism of neonicotinoid exposure among wild bee communities.
Neonicotinoids are applied to seeds before planting. The active compound is spread throughout the plant, which means insects ingest the chemical when they feed on the pollen and nectar of treated crops.
The exposure resulted in local extinctions of some species, the researchers 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,” said lead author, Dr Ben Woodcock.
The results suggest that neonicotinoids are affecting bee populations and diversity at a national scale. The results will help inform a European-wide review on the environmental risks of neonicotinoids by the European Food Standards Authority
According to the researchers, the data suggest that neonicotinoid use is correlated with wild bee biodiversity losses at a national scales and has implications for the conservation of bee communities in intensively farmed landscapes. The results add to an extensive body of evidence that will inform the review of the risks neonicotinoid pesticides pose to bees being undertaken by the European Food Safety Authority , with results due early next year.
“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,” Woodcock said.