Rising Temperatures Threaten Bumblebee Populations Worldwide

In a new study, researchers have identified rising temperatures as a potential cause for the decline in bumblebee populations worldwide. The study, published in Frontiers in Bee Science, suggests that global warming is making it difficult for bumblebees to build livable nests where their young can develop properly.

“The decline in populations and ranges of several species of bumblebees may be explained by issues of overheating of the nests and the brood,” said Dr Peter Kevan of the University of Guelph, Canada, lead author of the article. “The constraints on the survival of the bumblebee brood indicate that heat is likely a major factor, with heating of the nest above about 35 degrees Celsius being lethal, despite the remarkable capacity of bumblebees to thermoregulate.”

Bumblebees Struggle to Adapt to Rising Temperatures

The researchers found that many bumblebee species around the world, living in various environments, have an optimal nest temperature of 28-32 degrees Celsius. This similarity may indicate that bumblebees have limited ability to adapt to rising temperatures, making it hard for them to stay within their thermal neutral zone — a range where they can maintain their body temperature without expending too much energy.

“Excessively high temperatures are more harmful to most animals and plants than cool temperatures. When conditions are cool, organisms that do not metabolically regulate their body temperatures simply slow down, but when temperatures get too high metabolic processes start to break down and cease,” said Kevan. “Death ensues quickly.”

Colony Survival Depends on Healthy Offspring

Bumblebee colonies act as “superorganisms,” where the reproductive success of the colony depends on the collective survival and reproduction of its members. If the nest becomes too hot to raise healthy larvae, the entire colony suffers, regardless of individual bumblebees’ adaptations.

The scientists call for more research into bumblebee nest morphology, material properties, temperature, and thermoregulation to help protect these crucial pollinators. Ground-penetrating radar and flow-through respirometry analysis could help researchers understand how different colonies and species cope with varying conditions and identify species with broader thermal neutral zones, which may be more resilient to climate change.

“We hope that future scientists may take the ideas we present and apply them to their own research on bumblebee health and conversation,” concluded Kevan.

As global temperatures continue to rise, it is crucial to understand the challenges faced by bumblebees and develop strategies to protect these essential pollinators from the threat of climate change.

Keyword: bumblebee decline