The evidence has been mounting for years that the world’s most widely used pesticides, neonicotinoids, harm bees and other pollinating insects. Now it seems the problem isn’t limited to Europe and North America, where the alarm was first sounded. It’s everywhere.
Starting in 2012, a team led by Alex Aebi of the University of Neuchâtel, Switzerland, asked travelling colleagues, friends and relatives to bring back honey when they went abroad. In three years they amassed 198 samples from every continent except Antarctica, and tested them for neonicotinoids.
They found that three-quarters of the samples contained at least one of the five neonicotinoid pesticides. Of those, nearly half contained between two and five different neonicotinoids.
Most worryingly, in 48 per cent of the contaminated samples, the neonicotinoids were at levels that exceeded the minimum dose known to cause “marked detrimental effects” in pollinators. “The situation is indeed bad for pollinators,” says Aebi.
“Finding neonicotinoids in honey is perhaps not surprising,” says Christopher Connolly of the University of Dundee, UK. After all, the pesticides are widely used. “But to find neuroactive levels, in so many samples at many global sites, is shocking.”
Bees survive the winter by eating honey, so the results imply they are chronically exposed to neonicotinoids. “Recent scientific evidence showed an increased sensitivity to neonicotinoids after frequent or long-term exposure,” says Aebi.
The fact that the honey contained cocktails of neonicotinoids may also be a problem. They all act on different receptor proteins in the nervous systems of the insects. Some chemicals can boost each others’ toxic effects over time, says Connolly. However, there is only indirect evidence of this happening with the neonicotinoids so far.
Frustratingly, we have the data to figure out how real-world levels of the pesticides affect bees, but not in a useful form. Farmers in Europe and North America record their use of neonicotinoids, says Connolly, but this data needs to be gathered into geographical databases. Such databases could reveal local correlations between pesticide use and insect health. Aebi and his team are now urging governments to start collecting the data.