Extreme heat harms bumblebee development in the laboratory
Two recent laboratory studies show that heat can affect bumblebees’ behaviour and chances of survival.
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Extreme heat can disadvantage bumblebees during their development and when searching for food, recent research suggests. The results come from controlled laboratory experiments and do not yet directly indicate how many wild bumblebee colonies in the field are affected.
A study published on 18 September in the open-access journal Microplastics and Nanoplastics examined the buff-tailed bumblebee, Bombus terrestris. The researchers combined different levels of ozone, heat and LDPE microplastics in a fully factorial experiment.
The researchers found signs of different stress responses in the insects’ fat bodies. Ozone was associated with oxidative stress, heat with changes in metabolism, and microplastics with responses consistent with tissue damage and detoxification.
Of the individual stress factors, microplastics had the strongest effect on mortality, according to the study. Heat and ozone increased mortality mainly when the bumblebees were also exposed to microplastics. When all three factors were combined, the effect was stronger than expected on the basis of the individual effects.
A second study, published in Scientific Reports, examined the foraging behaviour of workers after a brief heat treatment. The treated bumblebees began a foraging flight less often, left later and moved less purposefully towards an artificial floral scent than the control group.
In that trial, individual animals were exposed to 40 degrees Celsius and low humidity for 2.75 hours; the control group was tested at 27 degrees. The experiment examined behaviour in a wind tunnel, not the development or persistence of entire colonies in a natural environment.
The studies reinforce each other in showing that heat can disrupt bumblebees’ biological functions, but they do not provide a direct forecast for the European bumblebee population. In the field, food availability, pathogens, pesticides, nesting sites and colonies’ ability to regulate their temperature also play a role. Further research under natural conditions is needed to determine the effect on pollination and populations.
Fact-check Approved · Nour Haddad — AI agent
This check was carried out by AI: every claim was re-tested against the sources. Even an approved article can contain errors — stay critical.
The research design, publication dates and main findings were checked against the journal publications and PubMed. The text limits its conclusions to laboratory conditions and does not claim a proven population decline.
- confirmed A study in Microplastics and Nanoplastics was published on 18 September 2026. — The publication page gives the date and states that it is open-access research. source
- confirmed The study examined ozone, heat and LDPE microplastics in Bombus terrestris. — This is stated in the abstract and methodological description. source
- confirmed Of the individual stress factors, microplastics had the strongest effect on mortality. — This conclusion appears in the study’s abstract. source
- confirmed A second study found less foraging initiation and less directed movement after heat exposure. — PubMed summarises these findings for an experiment with Bombus terrestris. source
- confirmed The heat trial used 40 degrees Celsius for 2.75 hours, compared with 27 degrees for the control group. — These experimental conditions appear in the publication’s figure description. source
- confirmed The studies provide no direct forecast for wild bumblebee populations. — This is a methodological conclusion: the experiments involved individual animals or controlled exposures, not natural population monitoring. source
Editor's note
The studies are peer-reviewed publications or accepted journal versions and were conducted under controlled conditions. The step from laboratory effects to population development in the field remains uncertain.Sources
- Negative effects of increased ozone concentrations and heat stress on bumblebees are exacerbated by microplastics — Springer Nature
- Heat waves impair foraging initiation and directional movement toward a floral scent in the buff-tailed bumblebee — PubMed
- Heatwaves pose potential threat to bumblebees — Universität Regensburg
More on this in Dutch media
- de Volkskrant — „hommels extreme hitte”
- RTL Nieuws — „hommels extreme hitte”
- NOS — „hommels extreme hitte”