Climate change study: how extreme events are increasing and animals will increasingly be affected multiple times

During an extreme heatwave in Australia, more than 72,000 flying foxes died within just a few days. The devastating Pantanal fires of 2019/20 are estimated to have killed 17 million vertebrates.

Such events are no longer isolated cases. A new study, published in Nature Ecology & Evolution and led by the Potsdam Institute for Climate Impact Research (PIK), shows that climatic extreme events are not only becoming more frequent, they are increasingly occurring at the same time. By the year 2085, more than one third of the habitats of terrestrial vertebrates could be simultaneously affected by multiple extreme events such as heatwaves, droughts, or fires.

To capture these risks systematically, the current study combines global climate models with climate impact models. While climate models simulate changes in temperature and precipitation, impact models calculate their ecological consequences, such as the frequency and intensity of such extreme events.

On this basis, the researchers calculated for almost 34,000 terrestrial vertebrate species—mammals, birds, amphibians, and reptiles—what share of their range could in future be affected by such extreme events. Only events that were very rare compared with the climate of the preindustrial period (1850-1900) are considered “extreme,” such as exceptional heatwaves.

The results relate to a scenario close to today’s climatic trajectory (SSP3-7.0): climate change that continues steadily, but does not spiral completely out of control. At the same time, the study shows that consistent climate action can significantly limit the risks.

How much is at stake is also illustrated by other study results: With global warming of 5.4 °C, up to 30% of all animal species could ultimately go extinct. Earlier PIK model calculations also suggest that the Earth could warm by up to 7 °C by the year 3000 even under moderate emissions.

By 2050: heatwaves as the new normal

The clearest and at the same time most consequential change concerns heat. In the coming decades alone, heatwaves could become an omnipresent stress factor for animals. The researchers led by Stefanie Heinicke show that by 2050, on average, 74% of terrestrial vertebrate habitats will regularly be affected by heatwaves.

If current trends continue, this share will rise to as much as 93% by 2085. Extreme heat would then no longer be an exceptional event, but part of a new climatic reality—in almost all habitats worldwide.

This has serious consequences for animals. High temperatures lead to dehydration, heat stress, and altered behavior patterns. Many species are forced to reduce activity, seek cooler refuges, or adjust reproduction. At the same time, survival and reproductive rates decline—especially in species that are already under pressure.

How many species are specifically affected is illustrated by the figures for 2050: around 9,400 bird species, about 4,700 mammal species, roughly 6,800 amphibian species, and about 9,100 reptile species will each be regularly exposed to heatwaves across at least half of their range.

Given that there are roughly 11,000 bird species, 12,500 reptile species, nearly 9,000 amphibian species, and about 6,800 mammal species worldwide, the scale becomes clear: this affects not just a few sensitive species or regions, but a large share of global biodiversity.

What matters here is that the study shows where species are exposed to extreme events, but not directly how many of them will go extinct. How severe the effects of climate change actually become also depends on how sensitive species are and how well they can adapt.

More fires, droughts, and floods

Alongside increasing heat, other extreme events are also changing significantly—less universally, but often with equally devastating consequences.

Wildfires come second. By 2050, around 16% of vertebrate habitats could already be regularly affected by fire; by 2085, this share rises to around 25%. Richly biodiverse regions such as the Amazon, parts of Africa, and Southeast Asia are affected first and foremost. Rising temperatures and altered precipitation patterns promote the emergence and spread of fires there.

Fires do not act exclusively negatively, however. Some specialized species benefit in the short term from open areas or altered living conditions. For example, the Riffian skink (Chalcides colosii) has been documented more frequently in disturbed habitats after fires. Against this, however, stand large-scale events that affect entire animal communities—as in the Pantanal, where millions of vertebrates perished within a short time.

Droughts are also increasing significantly. Their share rises from about 8% of habitats by 2050 to around 14% by 2085. Amphibians react especially sensitively because they depend on moist habitats and lose important refuges and breeding sites during dry periods.

Here, too, some species can benefit in the short term. In the ornate chorus frog (Pseudacris ornata), for example, drought periods have been observed to lead under certain conditions to lower competition or less predation. Overall, however, the negative effects clearly predominate.

Floods play a smaller role globally, but are also increasing. By 2050, about 3% of habitats could be affected; by 2085, around 5%. Despite these comparatively low shares, floods can have devastating local consequences—for example through habitat destruction, the drowning of juveniles, or the spread of disease.

What matters is not only the frequency of individual events, but also their spatial concentration. Many of these changes affect precisely biodiversity hotspots, that is, regions with especially high species richness. This raises the risk that entire ecosystems come under pressure simultaneously.

The real problem: several extremes at the same time

Perhaps the most important finding of the study is not the increase in individual extreme events, but their interaction. In future, many species will no longer be confronted with only one threat, but with several at the same time or in rapid succession.

By 2050, around 14% of terrestrial vertebrate habitats could already be affected by at least two different extreme events—for example heatwaves and droughts, or fires and floods. By 2085, this share rises to around 36%. That would mean more than one third of all habitats being regularly exposed to several climatic stressors at once.

The trend becomes even clearer when looking at entire ecoregions such as rainforests, savannas, or tundras. Whereas today only comparatively few regions are affected, their number could rise by the end of the century from 22 to 236 ecoregions in which at least half the area is shaped by multiple extreme events.

Why combinations are so dangerous

Many species can at least temporarily compensate for a single extreme event. Animals can move away, adjust activity, or draw on reserves. But these strategies reach their limits when several burdens occur at the same time or amplify one another.

For example, drought and fire together lead to far greater vegetation loss because dried-out landscapes burn faster and across larger areas. Heat combined with water scarcity additionally increases stress for animals and can significantly raise mortality. And when fires strike already fragmented habitats, the refuges critical for survival are often missing.

These effects do not merely add up—they reinforce one another. What on its own might still be bearable can in combination quickly become a tipping point.

How serious this effect is can be seen in studies of the Australian fires of 2019/20: in regions previously affected by drought, animal and plant populations declined by 27 to 40% more than in areas without additional stress factors.

Particularly at risk: species with small ranges

Species with small ranges are among the biggest losers of climate change. Their habitat is often highly limited, and therefore so are their possibilities for responding to changing conditions. A 2024 study identifies the size of the range as one of the most important factors in extinction risk—a relationship that appears across different animal groups.

Whereas widespread species can at least theoretically shift to cooler or less affected regions, this option is usually absent in species with narrow distributions. When extreme conditions occur there, they hit the entire population at once. This is especially evident in mountain species, which shift to higher elevations as temperatures rise—until they reach the summit and no suitable habitat remains.

The study itself offers a concrete example: the white-tailed black cockatoo (Calyptorhynchus latirostris), which occurs only in southwestern Australia, lost around 60% of its population after a single extreme heatwave. Specialized species in particular, tied to specific habitats, react with extreme sensitivity to extreme conditions.

Another example is the Bramble Cay melomys (Melomys rubicola). It lived only on a small island in Torres Strait between Australia and Papua New Guinea and is regarded as the first mammal to have gone extinct directly as a result of climate change. Rising sea levels and increasingly severe storm events completely destroyed its habitat—there was nowhere to retreat.

This shows that extreme events do not act only in the long term; they can also reduce populations abruptly and drastically. And the smaller the range, the greater the risk that a single event is enough to push a species to the brink of extinction.

Can species adapt?

The answer is: partly. Many species have remarkable adaptive capacities. They can change behavior, use new resources, or respond to altered environmental conditions. For example, mountain gorillas (Gorilla beringei) have been observed seeking water more frequently as temperatures rise in order to stabilize their fluid balance.

But these adaptations have limits. Evolutionary change takes time—often many generations. Climate change, by contrast, is advancing at a pace many species can no longer compensate for. Extreme events are becoming more frequent, more intense, and increasingly overlapping.

Added to this is the fact that many species already live close to their tolerance limits today. Additional stress from heat, drought, or habitat loss can then quickly mean that even small changes have major consequences.

Lead author Stefanie Heinicke summarizes the results of the climate-change study:

What matters is how strongly we slow climate change

How severely species will suffer from extreme climate events in future depends decisively on how consistently climate change is limited. In a world with effective climate protection measures—in line with the Paris Agreement—far fewer species and habitats would be affected by extreme events. Many ecosystems could stabilize, and at least some species would have a chance to adapt.

The situation looks very different if emissions continue to rise: in that case, up to 44% of habitats could be affected by several extreme events simultaneously by the end of the century. That would mean almost every second region experiencing a combination of heat, drought, fire, or flooding.

The difference between these pathways is human-made. Climate change is no longer merely a physical or meteorological problem, but a profound biological crisis affecting animals, plants, and ultimately humans as well.

With every further tenth of a degree of global warming, the risk increases that entire species communities will be destabilized. Tipping points are drawing closer—thresholds beyond which even ecosystems that were previously stable no longer return to their original state, but instead change permanently and irreversibly.

Climate protection is therefore always also species protection—and vice versa. Intact ecosystems are important carbon sinks and stabilize the climate. If they are lost, climate change is further amplified. Biological diversity can be preserved only if it becomes possible to
– reduce emissions quickly and consistently,
– protect and restore intact habitats,
– implement political measures effectively
– and systematically integrate climate risks into conservation planning.

The faster and more decisively action is taken, the greater the chance that species and ecosystems will survive this development.

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Sources

• Heinicke, S., Zantout, K., Kühl, H. S. et al. (2026). Land vertebrates increasingly exposed to multiple extreme events by 2085. Nature Ecology & Evolution. https://doi.org/10.1038/s41559-026-03050-0
• Potsdam Institute for Climate Impact Research (PIK). (2026, 24 April). One third of the habitats of terrestrial animal species threatened by multiple extreme events by 2085.
  https://www.pik-potsdam.de/de/aktuelles/nachrichten/ein-drittel-der-lebensraeume-von-an-land-lebenden-tierarten-bis-2085-von-multiplen-extremereignissen-bedroht