Researchers at the University of Regensburg have issued a concerning finding: climate change-driven heatwaves may pose a severe threat to bumblebees, critical insect pollinators whose populations are already declining. “The increasing frequency and intensity of weather extremes, such as heatwaves, may addf significant stress to these key species”, says Dr. Christoph Kurze, the lead researcher of this study at the University of Regensburg. "That's why we asked what effect short, varying thermal heat exposure and duration would have on the pupal development in bumblebees, specifically the buff-tailed bumblebee (Bombus terrestris)," said Sandra Lau?er, a student who conducted this study for her Bachelor thesis.

The study revealed that thermal stress for a few days already drastically reduced pupal emergence. Furthermore, the findings suggest that increased extreme thermal stress negatively impacts bumblebee pupal development, which was also indicated by an increase in wing deformities. These deformities affect bee's ability to fly and forage, thereby reducing the colony's overall success and affecting their pollination service. Bumblebees are essential components of ecosystems, performing crucial pollination services across the Northern Hemisphere, including Europe. “They are also key commercial pollinators, used, for example, in greenhouses for the pollination of crops like tomatoes,” the researchers stated.

While the Regensburg team's approach was mechanistic, conducted in a controlled laboratory setting rather than naturally living colonies, the findings are highly relevant. The study serves as a critical indicator of vulnerability. "We expect even greater vulnerability in more cold-adapted bumblebee species," Kurze added, "suggesting more sensitive bumblebee species face an even greater risk as heatwaves increase in frequency and intensity."

 

Publication:

Lau?er, S., & Kurze, C. (2025). Impact of thermal stress during pupal development in a key pollinator. Proceedings of the Royal Society B, 292:20252029. doi: doi.org/10.1098/rspb.2025.2029