Risks of amphibian extinctions from climate change rising rapidly

The risks of amphibian extinctions have been laid bare in a stark new study.

Compiled by over 100 scientists from all over the world, the paper reveals that over 40% of more than 8000 amphibian species could die out in the coming decades. This is the highest of any major animal group on the conservation Red List, which assess the threatened status of species, with salamanders and newts particularly at risk.

Climate change has been highlighted as a particular threat to amphibians, being the key cause of declines in 40% of species.

Jennifer Luedtke Swandby, one of the study’s lead authors, says, ‘As humans drive changes to our planet, amphibians are becoming climate captives, unable to move very far to escape the climate change-induced increase in frequency and intensity of extreme heat, drought and hurricanes.’

‘Our study shows that we cannot continue to underestimate this threat. Protecting and restoring forests is critical not only to safeguarding biodiversity, but also to tackling climate change.’

While the paper, published in Nature, highlights the bleak future many amphibians face, it does show some signs for hope. Over 60 species have recovered in the past 40 years as a result of conservation action, with wider protections suggested to help turn other declines around.

Dr Simon Loader, Principal Curator in Charge of Vertebrates at the Natural History Museum and a co-author of the research, says, ‘More than 8,600 species of amphibians have been scientifically discovered and named worldwide. It’s a major international task to assess the conservation status of all these species.’

‘Analysing the resulting data provides important insights into current threats faced by species today—which is key for planning ongoing conservation management programmes. But these data are also valuable in discovering how the global picture for amphibians has changed since the 1980s, with some worrying findings.’

How have the threats facing amphibians changed?

Over the past 40 years, the number of amphibians driven to extinction has been gradually rising, from 23 species in 1980, to 33 in 2004 and 37 in 2022. As a result, distinct species such as the gastric-brooding frogs which incubated their eggs in their stomach have been lost for ever.

But it’s possible that these species are just the tip of an extinction iceberg. There are more than 185 other amphibians that haven’t been seen for decades, and while there’s not enough evidence to prove they’re extinct, it’s a real possibility.

Amphibians tend to face three key threats: habitat loss, disease and climate change.

Habitat loss affects the most species, with the conversion of habitats into farmland thought to impact around 77% of amphibians overall. It’s thought to be responsible for the extinction of the Jalpa false brook salamander, which disappeared after logging and cattle grazing destroyed the Guatemalan forests it called home.

While the impacts of habitat loss are far reaching, it’s only thought to be the main cause of decline in about one third of species. Instead, disease has historically played a more important role.

Over the past century, amphibians have been the victims of a pandemic caused by the disease chytridiomycosis, a result of the fungus Batrachochytrium dendrobatidis which causes damage to their skin. While the threat of disease affects fewer species than habitat loss, the sudden declines chytridiomycosis causes are often more devastating.

During the 1980s, for instance, the sharp-snouted day frog was widespread across Queensland, Australia, but within a decade of being infected by the fungus the frog’s numbers crashed, and following a final sighting in 1997 it was declared extinct in 2021.

There is, however, hope for frogs as in recent years some amphibians have begun to adapt to chytridiomycosis. Today, this means that disease is the main cause of declines in only a quarter of frogs, rather than 58% 40 years ago.

Instead, climate change has taken its place as a new key driver of declines. It is now the most common cause of declines in more than 40% of amphibians. This is mostly due to rising temperatures and increasing periods of drought which limit the amount of water available for amphibians to keep them and their offspring moist.

The rising impact of climate change has concerned researchers because it can exacerbate other causes of amphibian decline. Different weather conditions could, for example, help emerging diseases like Batrachochytrium salamandrivorans spread deeper into Europe and across to the Americas, infecting new species of amphibians.

Can amphibians recover?

The new study documents many reasons to be concerned about amphibians, but it also finds some hope as over the last 40 years 120 species have improved their conservation status.

Conservation action was responsible for turning around the fortunes of 63 species, mostly by taking steps to protect their habitat. In the Western Ghats, for instance, the Wildlife Trust of India has dug out pools that are supporting the breeding of the Anaimalai flying frog and other threatened species.

The other 57 species are recovering by themselves. Species such as the green and golden bell frog, which were once hit hard by chytridiomycosis, appear to be recovering. Although the exact reasons for this are not clear, it’s possible that the species have developed a resistance to the disease. The researchers also suggest that other factors, such as having a stable habitat, may also play a role.

Although these species are recovering, there are many others whose future is uncertain, with over 600 species still waiting to have their conservation status assessed and over 900 more that are categorised as ‘Data Deficient’. This particularly affects a group of limbless, mostly soil-dwelling amphibians known as caecilians.

Dr David Gower, an expert in amphibians from the Natural History Museum and another co-author of the study, says, ‘Though thousands of amphibian species are known about, we know very little about their ways of life of many of them.’

‘Without detailed information on their population trends or where they live, it is difficult to accurately categorise species on the Red List. Overcoming this is a major challenge in amphibian conservation biology.’

To combat these unknowns, work is already underway on a new assessment of amphibians to cover the next 20 years. In the meantime, the findings of the paper can help to drive targeted conservation action by highlighting threatened species and regions.

Dr Simon Loader adds, ‘We’re in the process of adding new species to the global inventory and re-assessing the conservation status of known species. These assessment data help to prioritise conservation action in areas where we see most evidence of change and need.’

Protecting important amphibian habitats will be especially important for both known and unknown species, giving them a better chance of surviving through the Anthropocene.