Up to half of all insect species in the Amazon could face life-threatening heat stress if global temperatures continue rising unchecked, according to a study published in Nature by an international research team led by scientists at Julius-Maximilians-Universität Würzburg (JMU) and the University of Bremen.
The study examined the temperature tolerance limits of more than 2,000 insect species, making it one of the broadest assessments of tropical insect vulnerability to date. Field data collected in 2022 and 2023 spanned multiple elevations across East Africa and South America, including cool mountain forests, hot tropical rainforests, and lowland savannas.
Lowland Species Carry the Greatest Risk
The central finding is that insects do not simply adjust their heat tolerance in step with their local environment. Altitude matters significantly. Species living at higher elevations show some short-term capacity to increase heat tolerance, but insects in tropical lowlands, where biodiversity is densest, largely lack that flexibility.
“While species at higher altitudes can increase their heat tolerance, at least in the short term, many lowland species largely lack this ability,” said Dr. Kim Holzmann, study author and researcher at the Chair of Animal Ecology and Tropical Biology at JMU.
That distinction carries weight. Tropical lowlands hold the planet’s highest concentrations of insect diversity, and those are precisely the populations least equipped to handle warming conditions.
Biology Sets Hard Limits on Adaptation
The team also analyzed the genomes of many species to probe why some insect groups cope with heat better than others. The answer appears to lie in protein biology. The thermal stability of proteins varies considerably across insect groups, and those structural properties are deeply conserved across evolutionary lineages.
“These properties are relatively conserved in the evolutionary family tree of insects and can only be changed to a limited extent,” said Dr. Marcell Peters, an animal ecologist at the University of Bremen. “The results suggest that fundamental characteristics of heat tolerance are deeply rooted in biology and cannot be quickly adapted to new climatic conditions.”
In practical terms, the insects most at risk cannot simply evolve their way out of the problem fast enough to keep pace with projected warming.
Ecosystem Consequences Run Deep
Insects account for roughly 70 percent of all known animal species, with the majority concentrated in tropical regions. They function as pollinators, decomposers, and predators across virtually every terrestrial ecosystem. Widespread heat stress among these populations would not stay contained to the insects themselves.
“Rising temperatures could have a massive impact on insect populations, especially in regions with the world’s highest biodiversity,” Peters said. “Since insects fulfill central functions in ecosystems as pollinators, decomposers, and predators, there is a threat of far-reaching consequences for entire ecosystems.”
The study was conducted with support from the German Research Foundation and used DNA barcoding to identify species at the genetic level, a method that allowed the team to work across a range of poorly studied insect groups where conventional identification would have been impractical.
Holzmann put the Amazon scenario plainly: “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.”
Photo by Mark Kuiper on Unsplash
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