Bees may be losing their sense of smell due to heatwaves

Heatwaves are impairing the ability of bumble bees to detect floral scents, posing a serious threat to their role as pollinators, according to a new study.

The research shows that exposure to extreme temperatures can significantly reduce bees’ capacity to smell flowers, potentially disrupting their foraging behaviour and affecting the crops that depend on them for pollination.

Bumble bees are crucial to agriculture, pollinating crops that make up about one-third of the food supply, including vegetables, fruits, nuts, and legumes.

However, bee populations have been declining due to habitat loss and climate crisis, with rising temperatures exacerbating the problem.

Researchers from University of Würzburg aimed to investigate how these rising temperatures impact bumble bees’ ability to detect floral scents – a key factor in their ability to locate food.

The research team conducted experiments on 190 bumble bees from two species, Bombus pascuorum and Bombus terrestris, both common in Europe.

The bees were subjected to simulated heatwaves by being placed in tubes where the temperature was raised to 40 degrees Celsius for nearly three hours.

Afterwards, their antennae were removed and attached to electrodes to measure their electrical responses to three floral scents: ocimene, geraniol, and nonanal. These scents are commonly found in flowers and play a vital role in attracting pollinators.

The findings were significant. Heat exposure reduced the bees’ antennal response to all three scents by up to 80 per cent, indicating a sharp decline in their ability to detect these essential floral signals.

“The results are pretty clear: There is an effect of heat waves on bumble bee physiology,” Coline Jaworski, a field ecologist at France’s National Institute for Agricultural, Food and Environmental Research, who was not involved in the new study, said, according to Science.org.

This reduction in scent detection could severely hinder their foraging efficiency, as bumble bees rely on their sense of smell to identify the best flowers for nectar, according to the paper published in Proceedings of the Royal Society B on Wednesday.

If bumble bees struggle to locate food, it could lead to reduced pollination, which in turn would affect plant reproduction and crop yields.

“If pollinators are not coming for a few days … then there’s no pollination, no seeds, and no descendants – that’s it,” Ms Jaworski said.

Adding to the concern, the study found that the bees’ ability to recover from heat exposure was limited. In most cases, their antennal responses did not return to normal even after a 24-hour recovery period at cooler temperatures.

This suggests that the damage caused by heatwaves could have long-lasting effects on bumble bee populations.

The wild-sourced Bombus pascuorum was particularly affected, showing less resilience compared to the commercially sourced Bombus terrestris.

Furthermore, female worker bees, which are responsible for collecting food for the colony, were more susceptible to heat than males.

The implications of these findings are significant. Bumble bees are vital for the pollination of many crops, and their decline could have a direct impact on global food production.

As climate crisis continues to drive up temperatures and increase the frequency of heatwaves, understanding the effects on pollinators like bumble bees becomes increasingly critical. The study’s findings suggest that extreme heat could disrupt the delicate balance between plants and their pollinators, leading to broader ecological consequences.

While this study focused on bumble bees, the researchers noted that other pollinators could be similarly affected by rising temperatures.

Future research is needed to explore the impact on different species, particularly those that do not live in colonies and cannot store food, making them more vulnerable to environmental changes. The ability of pollinators to adapt to a warming world is crucial for maintaining the health of ecosystems and the stability of food supplies.

Last year was the hottest year on record. As heatwaves become more frequent and intense, the survival of species like bumble bees may be at risk, with potentially far-reaching consequences for agriculture and the environment.

Ahead of the launch of The Independent’s Climate 100 List next month we are celebrating some of the leading lights being honoured for their work tackling the climate crisis and protecting nature.

Look out for details on how to join our Climate 100 event in the coming days. It’s set to be a landmark celebration of the top 100 global climate thinkers, innovators and leaders shaping the green economy, with some exciting speakers yet to be announced.