Heatwaves impair bumblebees’ ability to detect floral scents, study finds

Climate change affects ecosystems in many ways. One of the ways it affects ecosystems is through increasingly long and intense periods of heat, which affect essential natural processes such as pollination. A team of researchers from the Julius Maximilians University of Würzburg (JMU) has studied in more detail the effect of heat on a particular player in these processes: the bumblebee.

The work is published in the journal Proceedings of the Royal Society B: Biological Sciences.

“Bumblebees are important pollinators in natural and agricultural systems. They are therefore of great economic and biodiversity value,” says study leader Dr Sabine Nooten. These furry insects are also extremely sensitive to heat events, as they are particularly well adapted to colder habitats.

As pollinators, bumblebees are guided by the odors emitted by plants. These chemical signals not only reveal the location of plants, but also contain information about the condition of flowers.

In this experiment, the bumblebees were exposed to temperatures of 40°C in tubes, which had serious consequences. “We found that the heat significantly impairs the bumblebees’ ability to detect floral scents,” Nooten explains. They practically lose their sense of smell.

Deterioration of up to 80% has been observed in workers. Males have lost up to 50% of their sense of smell. It has also been found that wild bumblebees have even more problems with heat than commercially used animals.

Even a subsequent regeneration period at appropriate temperatures did not immediately lead to improvement: 24 hours after thermal testing, most samples still showed alterations.

The study confirms how insect-plant interactions are strongly influenced by climate change. Heat waves therefore play a key role in this regard. These results could prove important for future species conservation initiatives.

A follow-up project based on the results of the study has already been approved, Nooten explains. “Now that we have discovered that heat waves alter the physiological processes of bumblebees to detect flower odours, we are now focusing on the behavioural aspect. We will test how the foraging behaviour of bumblebees is affected by experimental heat waves.”