How Temperature Changes Affect Bees and Pesticides

Insights from Imperial College London

A recent study from Imperial College London reveals that temperature changes can influence how pesticides affect bee behavior. This research highlights that extreme temperature events due to climate change could increase the impact of pesticides on bee populations and their pollination services.

Neonicotinoids, a class of pesticides, are known to harm bees and other insects, contributing to population declines. However, bees’ responses to these pesticides vary globally, suggesting other factors are involved. The study, published in Global Change Biology, examined six bumblebee behaviors under two pesticides (imidacloprid and sulfoxaflor) at temperatures of 21, 27, and 30°C.

Four behaviors—responsiveness, movement likelihood, walking rate, and food consumption rate—were more affected by imidacloprid at lower temperatures, indicating that cold snaps could increase pesticide toxicity. However, flight distance was most affected at the highest temperature, showing a sharp decline at 30°C.

Dr. Richard Gill, the lead researcher, explained that the drop in flight performance at high temperatures suggests a ‘tipping point’ in bees’ tolerance to combined temperature and pesticide exposure. This effect occurs over just three degrees, highlighting the dynamic risk of pesticides with temperature changes.

As climate change progresses, bees will face more frequent exposure to pesticides and extreme temperatures. This study aims to inform appropriate pesticide concentrations and application times across different climates to protect pollinators like bees.

Flight distance is crucial for pollination, affecting foraging potential and food security. Although the tropics are generally hotter, temperate regions like the UK may experience stronger pesticide effects due to larger temperature ranges. Bees are vital for pollinating cereal crops, legumes, and fruit trees, and as food supply diversifies, their pollination services will be in higher demand.

First author Daniel Kenna emphasized the importance of environmental context in assessing pesticide toxicity, especially under future climate change scenarios. Co-author Dr. Peter Graystock noted the significance of these results for developing a toxicity forecast framework to predict bee population responses to climate change in agricultural landscapes.

The research team plans further studies across temperature gradients to better understand how toxicity effects scale with temperature and identify tipping points across various species.