A new study suggests many insects, especially in the tropics, are already close to their heat limits. Even as the planet warms, a large share of species may not be able to “train” their bodies to cope with higher temperatures.
The concern is not just about insects disappearing. It is about what happens to ecosystems when pollination, decomposition, and natural pest control begin to fail.
An international research team measured heat tolerance across more than 2,000 insect species and compared those results with genetic clues about how stable their proteins are under stress.
The researchers tested insects across a wide range of habitats, from cool mountain forests to hot lowlands in East Africa and South America, building a picture of where adaptation seems possible and where it appears sharply limited.
Mountain insects and lowland insects
The study challenges an assumption that sounds intuitive: that insects living in warmer places should be better at handling heat, and that species can adjust their tolerance as conditions change. The researchers argue the reality is more uneven.
“Current evaluations of the heat tolerance of insects such as moths, flies, and beetles paint a differentiated – and at the same time alarming – picture,” said lead author Kim Holzmann, a researcher at Julius-Maximilians-Universität Würzburg (JMU).
According to Holzmann, the ability to deal with high temperatures does not simply track local climate.
According to the study, insects’ ability to tolerate high temperatures does not simply adapt to their respective environment.
“While species at higher altitudes can increase their heat tolerance, at least in the short term, many lowland species largely lack this ability,” Holzmann said.
That contrast matters because lowland tropical regions host vast numbers of insect species. If many of those species cannot increase their heat tolerance, rising temperatures could push them into dangerous territory faster than expected.
Consequences beyond insects
The researchers stress that insects are not a niche concern. They sit at the center of how many ecosystems function. When insect populations change, everything from plant reproduction to soil health can change with them.
The scientists describe the risks in particularly stark terms for tropical regions, where biodiversity is high and warming can be relentless.
The study, published in Nature, makes it clear that tropical insects have only a very limited ability to adapt to climate change.
“Rising temperatures could have a massive impact on insect populations, especially in regions with the world’s highest biodiversity,” said Marcell Peters, an animal ecologist at the University of Bremen.
“Since insects fulfill central functions in ecosystems as pollinators, decomposers, and predators, there is a threat of far-reaching consequences for entire ecosystems.”
The logic is simple. If insects can’t cope with heat, their numbers may drop, their activity patterns may shift, or their life cycles may be disrupted.
Any of those changes can ripple outward. Pollination can become less reliable. Decomposition can slow down or become uneven. Predator-prey relationships can break into new, unstable patterns.
Limits may be locked into insect biology
One of the study’s most sobering points is that heat tolerance might not be flexible in the way people often assume.
The researchers found clear differences between insect groups, and they suggest those differences are not just about where insects live. They may be tied to deep biological constraints.
There are also striking differences between different insect groups. The experts attribute these differences to the structure and heat stability of proteins.
“These properties are relatively conserved in the evolutionary family tree of insects and can only be changed to a limited extent,” Peters said.
“The results suggest that fundamental characteristics of heat tolerance are deeply rooted in biology and cannot be quickly adapted to new climatic conditions.”
If heat tolerance is closely linked to protein stability, and if that stability is slow to change over evolutionary time, then rapid climate warming becomes a serious mismatch. Species may face temperatures that outpace their ability to adapt.
This also helps explain why some insects might do better than others even in the same environment. It may not be about effort, behavior, or acclimation alone. It may be about how their biology is built at a molecular level.
The Amazon looks especially vulnerable
The scientists highlight the Amazon region as a place where future heat could become a critical stressor for a large portion of insect life.
The warning is not that every insect will vanish. It’s that many species could cross thresholds where normal activity becomes difficult or survival drops.
“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,” Holzmann said.
“Critical heat stress” suggests conditions where insects may not be able to function normally, reproduce reliably, or avoid lethal overheating during the hottest periods.
In a region as interconnected as the Amazon, losing large fractions of insect diversity could reshape ecosystems in ways that are hard to predict and hard to reverse.
A key reason the authors frame this as urgent is that insect heat tolerance is still poorly measured, especially in the tropics. That is striking given how dominant insects are in animal diversity.
Limited data is available
Insects account for around 70 percent of all known animal species, and most live in the tropics. Nevertheless, little is known about how well tropical insects cope with rising temperatures.
One reason for this is the low amount of experimental measurement data on temperature tolerance and the insufficient research on many insect groups available to date.
For the study, the scientists investigated the temperature tolerance limits of more than 2,000 insect species.
Data was collected in 2022 and 2023 at various altitudes in East Africa and South America, ranging from cool mountain forests to hot rainforests and lowland savannas.
The team also analyzed the genomes of numerous species to study the stability of their proteins and better understand why some insect groups tolerate heat better than others.
The genome work is important because it goes beyond describing what happens. It tries to explain why it happens. It links differences in heat tolerance to underlying biology that may not be easily “trained” into something new.
What this means going forward
The study leaves a clear message. Warming is not just an issue of shifting ranges northward or uphill. For many tropical insects, there may be very little uphill left, and very little spare tolerance to work with.
If lowland species can’t raise their heat limits, then protecting habitats alone may not be enough. The climate itself becomes the barrier.
The researchers are effectively calling for more attention to insect physiology, more measurement in under-studied regions, and more realism about how quickly living systems can adjust.
In the tropics, where insects support so much life, the margin for error may be thinner than we thought.
The study is published in the journal Nature.
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