A new study suggests that the impact of pesticides on bees’ behavior may become more uncertain under climate change due to the influence of temperature. Specifically, changing temperatures could increase the risk of pesticide exposure to bees.
The study’s findings reveal that the impact of pesticides on bee populations and their pollination services could amplify in the future, particularly during extreme temperature events linked to climate change.
Neonicotinoids, a class of pesticides, are known to adversely impact bees and other crucial insects, contributing to population declines. However, the responses of bees worldwide to this threat appear to differ, suggesting that other factors may be interacting.
A study published in Global Change Biology by researchers from Imperial College London has demonstrated that pesticides can affect various critical bumblebee behaviors that are crucial for their survival and ability to pollinate crops. The researchers also found that environmental temperature plays a significant role in determining the degree of this effect.
In their study, the researchers examined six distinct bumblebee behaviors under the influence of two different pesticides – imidacloprid and sulfoxaflor – at three different temperatures (21, 27, and 30°C). The study found that four of the behaviors – responsiveness, likelihood of movement, walking rate, and food consumption rate – were more significantly affected by imidacloprid at lower temperatures, indicating that colder temperatures could amplify the pesticide’s toxicity on behaviors essential for nest duties. However, the bumblebees’ flying ability was most strongly impacted by imidacloprid at the highest temperature, with a sharp decline in flight distance observed at 30°C, while there was no significant difference between 21 and 27°C.
“The drop-off in flight performance at the highest temperature suggests a ‘tipping point’ has been reached in the bees’ ability to tolerate the combined temperature and pesticide exposure,” comments lead author Dr. Richard Gill.
“This seeming cliff-edge effect happens over the span of just three degrees, which changes our perception of pesticide risk dynamics given such temperature changes can commonly occur over the space of a day.
“Furthermore, the frequency to which bees will be exposed to pesticides and extreme temperatures under climate change are predicted to increase. Our work can help to inform the right concentrations and application times of pesticides across different climatic regions of the world to help safeguard pollinators, such as bees.”
The ability to fly long distances is critical for pollination, as it impacts the bumblebees’ foraging capacity and plays a vital role in ensuring food security by supporting crop pollination.
Although tropical regions tend to be hotter, bumblebee populations in more temperate latitudes such as the UK may experience greater pesticide effects due to the larger temperature ranges. Bees are responsible for pollinating numerous significant crops such as cereals, legumes, and fruit trees. As our food supply diversifies, there will be a greater demand for their pollination services, but the challenges faced by bees, such as climate change and increased insecticide usage, are likely to increase.
The researchers suggest that their findings, which measure the connections between temperature and pesticide effects, could be beneficial in constructing models to evaluate the risks of pesticides in different parts of the world as the climate changes.
These “findings show that environmental context is crucial when assessing pesticide toxicity, particularly when projecting bee responses under future climate change,” adds First author Daniel Kenna.
According to co-author Dr. Peter Graystock from the Department of Life Sciences at Imperial College London’s Silwood Park, these findings are significant in creating a framework for predicting how bee populations will react to climate change while coexisting with intensive agricultural environments. This could aid in the development of a toxicity forecast framework.
The research team’s next goal is to conduct more extensive studies across various temperature gradients to investigate how toxicity effects scale with temperature and to pinpoint the exact tipping points across various species.
Source: 10.1111/gcb.16671
Image Credit: Getty
