Study finds common pesticide increasing bumblebee’s risk of extinction


August 15th, 2017

A common neonicotinoid pesticide threatens bumblebees with an increased risk of extinction, a new study has shown.

The study found that thiamethoxam, a neonicotinoid pesticide widely used on agricultural crops across the world, decreased the ability of bumblebee queens to start new colonies by more than a quarter.

The results of the new research carried out by scientists at the University of Guelph, Ontario, and Royal Holloway, University of London, were published in the journal Nature Ecology & Evolution on Monday.

In the study, half of a population of 300 bumblebees was fed syrup containing levels of thiamethoxam similar to those found in wild pollen and nectar. The research found that bumblebee queens exposed to the pesticide were 26 per cent less likely to lay eggs to start a colony.

Mathematical models of bumblebee populations were then used to estimate what this decline could mean in real world terms. According to the researchers, the bumblebees’ reduced ability to start colonies could cause collapses in wild bee populations.

Lead researcher, Professor Nigel Raine of the University of Guelph, said that the results had a “bigger impact” than researchers expected to see.

“Our modelling suggests it could have a major impact on population persistence and increases the chances a population could go extinct,” he added. “We urgently need to know more about how pesticides could be affecting other species.”

Dr Gemma Baron of Royal Holloway echoed these concerns, warning that the bumblebee “could die out completely” if queens don’t produce eggs or start new colonies.

In 2013, the European Commission issued a temporary ban on certain neonicotinoid pesticides, including thiamethoxam, due to links to the long-term decline in bees. The Commission is expected to call for a total ban on these pesticides later this year.

As neonicotinoid pesticides are the most widely used group of pesticide globally, Professor Vincent Jansen, also of Royal Holloway, added that it is “vital that we understand the effects of these pesticides on our wildlife before allowing their continued use”.

These findings follow another recent study which found that neonicotinoid pesticides pose a major risk to European honeybees and wild bees by lowering their overwintering and reproductive success.

The scientists behind this study later had to defend their findings from criticisms made by the pesticide giants Bayer and Syngenta, both of whom part-funded the study.

Bee populations have been declining in Europe since the 1980s. Today, 30 per cent of Irish bee species are threatened with extinction. This decline is thought to be linked to a range of factors, including habitat loss and degradation, the use of pesticides, and introduced pests and diseases.

About the Author

Lia Flattery

Lía is a former writer and Deputy Editor at Trinity News. She also has a BA in History and English Literature from Trinity College Dublin.