Wild bees that forage from oilseed rape crops treated with insecticides known as neonicotinoids are more likely to undergo long-term population declines than bees that forage from other sources, according to the findings of an 18-year study.
The new research covered 62 species of bee found in the wild in Britain and found a link between their shrinking populations and the use of neonicotinoid pesticides.
Neonicotinoids are used worldwide in a range of crops and have been shown in lab-based studies to be harmful to certain species of bee – notably commercial honeybees and bumblebees.
The European Union limited use of the chemicals – made and sold by various companies including Bayer CropScience and Syngenta – two years ago, after research pointed to risks for bees, which are crucial for pollinating crops.
Neonicotinoids were initially licensed for use as a pesticide in Britain in 2002. By 2011, the proportion of UK oilseed rape seeds treated with them was 83%, according to the researchers leading this latest study.
Going back to data from 1994 up to 2011, the scientists analysed how large-scale applications of neonicotinoids to oilseed rape crops influenced bee population changes.
The results, published in the journal Nature Communications, found that bees foraging on treated oilseed rape were three times more likely to experience population declines than bees foraging from other crops or wild plants.
Giving details at a briefing in London, Ben Woodcock, who co-led the study, said the average decline in population across all 62 species was 7.0%, but the average decline among 34 species that forage on oilseed rape was higher, at 10%.
Five of the 62 species studied declined by 20% or more, he said, and the worst affected declined by 30%.
Woodcock, an ecological entomologist at the Natural Environmental Research Council Centre for Ecology and Hydrology, said the findings showed the extent of the impact.
“Prior to this, people had an idea that something might be happening, but no-one had an idea of the scale,” he told reporters. “(Our results show that) it’s long-term, it’s large scale, and it’s many more species than we knew about before.”
Woodcock’s team said this should add to the body of evidence being considered in a review of neonicotinoid risks to bees being carried out by the European Food Standards Authority, expected to be completed by January 2017.
Christopher Connolly, a neurobiologist and bee expert at the University of Dundee, who was not directly involved in this research, said: “The evidence against neonicotinoids now exists in key bee brain cells involved in learning and memory, in whole bees, entire colonies and now at the level of whole populations of wild bees.”
Liberal Democrat MEP Catherine Bearder has urged the UK government to protect bees and other pollinating insects by keeping in place an EU ban on neonicotinoids post-Brexit.
“The evidence is now overwhelming that the use of neonicotinoids poses a major threat to bees and other pollinators. The Government must give guarantees that the current EU ban on these harmful pesticides will remain in place after Brexit," Bearder commented.
“Wild bees play a vital role in our ecosystem and UK farming, protecting them means ensuring our food security.”
Graeme Taylor, Director of Public Affairs at the European Crop Protection Association (ECPA), an interest group representing the pesticides industry, said the report was incomplete and potentially misleading.
"As with all new scientific studies related to our industry’s products we will analyse it carefully. However, an initial look suggests that the methodology used was too limited in scope, and whilst it may show a correlation between increased use of neonicotinoids and declines in wild bee populations it clearly does not prove that neonicotinoids are to blame.
The other important point to note is that despite acknowledging other causes for decline, the study only looks at one possible factor potentially impacting on the wild bee population, when numerous other factors such as availability of specific foraging plants, nesting habitats, and climatic conditions, may also have an influence. One further point of note is that the data used relates to only one neonicotinoid active ingredient but the author concludes that the correlation relates to all products in the UK: this makes the report incomplete, and potentially misleading.
Despite numerous attempts as an industry to form a cross-sector group to try and look at addressing all factors affecting bee population decline holistically, many important parties have declined to participate."
The European Commission has launched a rescue plan for Europe’s dwindling honeybee colonies.
In January 2013, it adopted a 24-month ban on three widely-used neonicitinoid pesticides that the European Food Safety Authority (EFSA) says pose “high acute risks” to pollinators.
Around 16% of Europe’s honeybee colonies disappeared between 1985 and 2005 – with greater losses recorded in England, the Czech Republic, Germany and Sweden – according to the EU-funded Status and Trends of European Pollinators (STEP) project.
Insects such as honey bees and wild bees help pollinate around 84% of Europe’s 264 crop species and 4,000 vegetable varieties, contributing an estimated €22 billion to the EU's economy, STEP says.
The EU-funded STEP project recommends several ways farmers can protect bee populations: try to avoid those pesticides known to have negative impacts on bees; reduce the use of herbicides which suppress flowering plants; leave uncultivated flower rich patches in farmland where pollinators can benefit from flowers and nesting resources; plant mass-flowering crops (oilseed, clover and field beans) as part of rotations to provide extra nectar and pollen for bees and other insects.