“Current evaluations of the heat tolerance of insects such as moths, flies, and beetles paint a differentiated — and at the same time alarming — picture,” says study author Dr. Kim Holzmann, a researcher at the Chair of Animal Ecology and Tropical Biology at Julius-Maximilians-Universität Würzburg (JMU).
The research suggests that insects do not simply adjust their heat tolerance to match their surroundings. “While species at higher altitudes can increase their heat tolerance, at least in the short term, many lowland species largely lack this ability,” Holzmann explains.
Climate Change Threatens Key Ecosystem Roles
The findings, published in Nature, indicate that tropical insects have only a limited capacity to adapt to a warming climate. According to study author Dr. Marcell Peters, an animal ecologist at the University of Bremen, rising temperatures could significantly disrupt insect populations, particularly in areas that host the planet’s greatest biodiversity.
“Rising temperatures could have a massive impact on insect populations, especially in regions with the world’s highest biodiversity,” Peters says. “Since insects fulfill central functions in ecosystems as pollinators, decomposers, and predators, there is a threat of far-reaching consequences for entire ecosystems.”
Protein Stability Limits Heat Adaptation
The researchers also discovered major differences among insect groups in how well they tolerate heat. These variations appear to be linked to the structure and thermal stability of proteins within their bodies.
“These properties are relatively conserved in the evolutionary family tree of insects and can only be changed to a limited extent,” Peters explains. “The results suggest that fundamental characteristics of heat tolerance are deeply rooted in biology and cannot be quickly adapted to new climatic conditions.”
The outlook for the Amazon region is especially concerning, Holzmann notes. “If global ecosystems continue to warm unabated, expected future temperatures will lead to critical heat stress for up to half of the insect species there,” so the JMU biologist.
Large Study Examines Heat Tolerance in 2,000 Species
Insects make up roughly 70 percent of all known animal species, and the majority of them live in tropical regions. Even so, scientists still know relatively little about how well tropical insects can cope with rising temperatures.
One reason is the lack of experimental data on temperature tolerance, as well as the limited research available for many insect groups. To address this gap, an international team of scientists carried out the study with support from the German Research Foundation.
The researchers examined the temperature tolerance limits of more than 2,000 insect species. Field data was gathered in 2022 and 2023 across different elevations in East Africa and South America, including cool mountain forests, hot tropical rainforests, and lowland savannas.
In addition to measuring temperature limits, the team analyzed the genomes of many species. This allowed them to investigate the stability of proteins and gain insight into why certain insect groups can handle heat better than others.
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