Bumble Bees Suffering From Loss of Smell After Heat Waves Struck the Planet Last Year, Finds Study

Extreme heat waves are not only a growing threat to humans but also to vital pollinators like bumble bees. A recent study published in the Proceedings of the Royal Society B reveals that heat waves can significantly impair bumble bees' ability to detect the scents of flowers they depend on for food. This discovery raises concerns about the potential impact of climate change on bee populations and the agricultural industries that rely on them.

Impact of Heat on Bumble Bee Physiology

Coline Jaworski, a field ecologist at France's National Institute for Agricultural, Food and Environmental Research, told Science.org that heat waves have a clear effect on bumble bee physiology. If these bees struggle to find their food sources, the consequences could reportedly be severe for crops that depend on their pollination. Without successful pollination, seeds won't form, leading to a decline in plant reproduction, which could have disastrous outcomes for food supply chains.

Bumble bees play a crucial role in pollinating various crops that contribute to about one-third of the global food supply. Despite their importance, bee populations have been on a steady decline, primarily due to habitat loss and climate change. Last year, the planet experienced record-breaking heat, and such conditions are becoming more frequent, correlating with the ongoing decline in bee populations, as per the study.

How Rising Temperatures Affect Bumble Bees

Bumble bees rely on their eyesight to locate flower patches and use their antennae to detect the scent of the most suitable flowers. Receptors in their antennae pick up scent molecules, which are then transmitted as electrical signals to their brains, helping them decide which flowers to visit. Sabine Nooten, an insect ecologist at Julius Maximilians University of Würzburg, told the publication how rising temperatures affect this vital process in bumble bees.

Nooten and her team reportedly conducted experiments on 190 bumble bees from two species commonly found in Europe: Bombus pascuorum and Bombus terrestris. They exposed the bees to a simulated heat wave by placing them in a tube where the temperature was raised to 40°C for nearly three hours, as per Science.org. Afterward, the team removed the bees' antennae and tested their electrical responses to three common flower scents: ocimene, geraniol, and nonanal.

The Long-Lasting Effects of Heat Exposure

The results showed that heat exposure significantly reduced the bees' antennal responses to these scents, sometimes by as much as 80 percent. Sandra Rehan, a molecular ecologist at York University, commented on the importance of this study, noting that 40°C is within the range of temperatures currently experienced in many parts of the world.

Worryingly, most of the heat-exposed bees' antennae failed to recover their ability to detect scents, even after a 24-hour recovery period in cooler conditions. This suggests that the damage caused by heat waves could have long-lasting effects on bumble bees' ability to forage effectively.

The study also found that the wild species B. pascuorum was less resilient to heat compared to B. terrestris. Additionally, female worker bees, which are responsible for gathering food for their colonies, appeared more vulnerable to heat exposure than male bees.

Implications for Future Research and Pollinator Health

Future research should explore whether other bee species and pollinators, such as hoverflies, suffer similar heat-induced damage. Jaworski warns that some solitary pollinators, like the carpenter bee, might be at even greater risk. These insects do not have the advantage of stored food in colonies and could face devastating consequences if they are unable to forage effectively due to extreme heat.

This research highlights the pressing need to understand and address the impacts of climate change on vital pollinators, as their decline could have far-reaching effects on global food security.