How extreme weather threatens amphibians

What happens to a frog when its pond dries up months too soon, or when a week-long heat wave bakes the forest floor? Unlike us, amphibians don’t have the luxury of turning up the air conditioner or finding bottled water at the store. Their lives are bound tightly to the rhythms of temperature and rainfall. And now, as climate change fuels more frequent and intense heat waves, cold snaps, and droughts, amphibians are being pushed into crisis.

A new study published in Conservation Biology by researchers at Goethe University Frankfurt and the Fraunhofer Institute in Germany takes a hard look at just how exposed amphibians are to these climate extremes. The team, consisting of Evan Twomey, Francisco Sylvester, Jonas Jourdan, Henner Hollert, and Lisa Schulte, analyzed global climate records spanning 40 years and matched them against the ranges of more than 7,000 amphibian species worldwide. Their conclusion is that vast numbers of frogs, salamanders, and caecilians (the lesser-known, burrowing amphibians) now live in regions where extreme weather is rapidly intensifying.

Amphibians are act as the climate sensors of nature. With thin, permeable skin that absorbs moisture from their surroundings, they thrive only in environments that balance water and warmth just right. A temporary pond that evaporates a few weeks early can doom an entire generation of tadpoles. A sudden cold spell can suppress their immune systems, leaving them open to deadly fungal infections. Even short-lived heat waves can kill larvae outright or cause bizarre side effects like sex reversal.

It’s no surprise, then, that amphibians are the most threatened group of vertebrates on Earth. The International Union for Conservation of Nature (IUCN) estimates that 41% of amphibian species are at risk of extinction. For decades, scientists have pointed to habitat loss, disease, and pollution as major culprits. Now, extreme climate events are joining that list with increasing force.

The research team took a systematic approach: using NASA’s MERRA-2 climate datasets and the standardized precipitation–evapotranspiration index (a drought tracker), they mapped where heat waves, droughts, and cold spells have intensified since 1980. They then overlaid these maps on IUCN’s global amphibian distribution data, covering 7,202 species. To count as “exposed,” a species had to have at least half of its habitat overlapping with zones where extreme events have become much more frequent. By this measure, exposure is extremely high. Specifically, 40% of amphibian species are now exposed to heat waves, 16% are exposed to droughts, and 3% are exposed to increasing cold spells.

The geography is uneven. Tropical frogs in the Amazon Basin and Madagascar, salamanders in Europe, and various amphibians in Central and South America emerge as especially vulnerable. In some of these regions, nearly every species is exposed to at least one type of extreme event.

The study highlights several regions where exposure is nearly universal. Let's look at them individually. In Madagascar, the island’s iconic frog family, Mantellidae, is in deep trouble. Almost all of its 215 species are exposed to more frequent heat waves, and half are also threatened by worsening drought. In the Amazon Basin and Atlantic Forest (South America), which are home to diverse frog families, these forests have seen sharp increases in both heat waves and droughts. In Europe, salamanders, long thought of as cold-adapted, are now at risk from intensifying droughts. Many rely on small ponds and streams that are drying earlier and more often. Finally, the Southern Cone region (Argentina, Chile, Uruguay, Paraguay) has seen more cold spells, not fewer. Local frog families like Rhinodermatidae and Batrachylidae are caught between cold stress and fungal disease outbreaks.

Numbers are one thing, but do these weather shifts actually affect survival? The team dug into IUCN’s Global Amphibian Assessment data, comparing conservation status changes over time. They found that since 2004, species living in areas with more heat waves and droughts were significantly more likely to be “uplisted”, that is, moved into a higher-risk category for extinction. In earlier decades (1980–2004), the main threat was disease, particularly chytrid fungus. But from 2004 to 2022, climate change, and specifically extreme events, emerged as a leading driver of decline.

Amphibians play outsized roles in ecosystems. They keep insect populations in check, recycle nutrients, and serve as food for countless other animals. Lose them, and entire food webs wobble. The authors suggest practical steps to prevent losing families of amphibians. For instance, creating shaded, humid refuges in forests, protecting riparian zones, digging small ponds, or even artificially irrigating breeding sites could buffer amphibians against the worst extremes. One striking example is the Kihansi spray toad in Tanzania, saved from extinction by a system that mimicked the natural mist of its lost waterfall habitat. More broadly, conserving intact habitats remains key. Forests, wetlands, and streams naturally regulate local temperatures and moisture, softening the blow of extreme weather.

If you want to learn more, read the original article titled "Quantifying exposure of amphibian species to heatwaves, cold spells, and droughts" on Conservation Biology at http://dx.doi.org/10.1111/cobi.70074.