by Lindsay Renick Mayer and Devin Murphy
Re:wild, October 4, 2023
Habitat destruction and disease are both well-documented causes of the decline of amphibians—among the most threatened animals on the planet—but a new paper analyzing two decades’ worth of data from around the world has found that climate change is emerging as one of the biggest threats to frogs, salamanders, and caecilians. The study was published today in the scientific journal Nature.
The study, “Ongoing declines for the world’s amphibians in the face of emerging threats,” is based on the second global amphibian assessment, coordinated by the Amphibian Red List Authority, which is a branch of the International Union for Conservation of Nature’s Species Survival Commission’s Amphibian Specialist Group, hosted and managed by Re:wild.
The assessment evaluated the extinction risk of more than 8,000 amphibian species from all over the world, including 2,286 species evaluated for the first time. More than 1,000 experts across the globe contributed their data and expertise, which found that two out of every five amphibians are threatened with extinction. These data will be published on the IUCN Red List of Threatened Species.
Between 2004 and 2022, a few critical threats have pushed more than 300 amphibians closer to extinction, according to the study. Climate change was the primary threat for 39% of these species. This number is expected to rise as better data and projections on species’ responses to climate change become available. Climate change is especially concerning for amphibians in large part because they are particularly sensitive to changes in their environment.
“As humans drive changes in the climate and to habitats, amphibians are becoming climate captives, unable to move very far to escape the climate change-induced increase in frequency and intensity of extreme heat, wildfires, drought and hurricanes,” said Jennifer Luedtke Swandby, Re:wild manager of species partnerships, Red List Authority coordinator of the IUCN SSC Amphibian Specialist Group, and one of the lead authors of the study. “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.”
Habitat destruction and degradation as the result of agriculture (including crops, livestock like cattle and livestock grazing, and silviculture), infrastructure development and other industries is still the most common threat, according to the paper. Habitat destruction and degradation affect 93% of all threatened amphibian species. Expanded habitat and corridor protection in the places most important for biodiversity is going to continue to be critical.
Disease caused by the chytrid fungus—which has decimated amphibian species in Latin America, Australia and the United States—and overexploitation also continue to cause amphibian declines. Habitat destruction and degradation, disease, and overexploitation are all threats that are exacerbated by the effects of climate change.
The study also found that three out of every five salamander species are threatened with extinction primarily as the result of habitat destruction and climate change, making salamanders the world’s most threatened group of amphibians. North America is home to the most biodiverse community of salamanders in the world, including a group of lungless salamanders abundant in the Appalachian Mountains of the eastern United States. Because of this, conservationists are concerned about a deadly salamander fungus that has been found in Asia and Europe, called Batrachochytrium salamandrivorans (Bsal), entering the Americas.
“Bsal has not yet been detected in the United States, but because humans and other animals can introduce the fungus to new places, it may only be a matter of time before we see the second global amphibian disease pandemic,” said Dede Olson, a research ecologist with the USDA Forest Service, member of the IUCN SSC Amphibian Specialist Group, and co-author on the paper.
The Nature paper provides an update to the 2004 landmark paper that was based on the first global amphibian assessment for the IUCN Red List, which revealed the unfolding amphibian crisis for the first time and established a baseline for monitoring trends and measuring conservation impact. According to this new study, nearly 41% of all amphibian species that have been assessed are currently globally threatened, considered critically endangered, endangered or vulnerable. This is compared to 26.5% of mammals, 21.4% of reptiles and 12.9% of birds.
Four amphibian species were documented as having gone extinct since 2004—the Chiriquí harlequin toad (Atelopus chiriquiensis) from Costa Rica, the sharp snouted day frog (Taudactylus acutirostris) from Australia, Craugastor myllomyllon and the Jalpa false brook salamander (Pseudoeurycea exspectata), both from Guatemala. Twenty-seven additional critically endangered species are now considered possibly extinct, bringing the total to more than 160 critically endangered amphibians that are considered possibly extinct. The assessment also found that 120 species improved their Red List status since 1980. Of the 63 species that improved as the direct result of conservation action, most improved due to habitat protection and management.
“The history of amphibian conservation itself proves how vital this information is,” said Adam Sweidan, chair and co-founder of Synchronicity Earth. “If the IUCN Red List had been updated on a similar scale in the 1970s that it is today, we could have traced the sweeping amphibian disease pandemic 20 years before it devastated amphibian populations. It isn’t too late—we have this wealth of information, we have the Amphibian Conservation Action Plan, but plans and information are not enough. We need to act. We need to act fast.”
Conservationists will use the information from this study to help inform a global conservation action plan, to prioritize conservation actions at the global level, to seek additional resources, and to influence policy that can help reverse the negative trend for amphibians.
“Amphibians are disappearing faster than we can study them, but the list of reasons to protect them is long, including their role in medicine, pest control, alerting us to environmental conditions, and making the planet more beautiful,” said Kelsey Neam, Re:wild species priorities and metrics coordinator and one of the lead authors of the Nature paper. “And while our paper focuses on the effects of climate change on amphibians, the reverse is also critically important: that the protection and restoration of amphibians is a solution to the climate crisis because of their key role in keeping carbon-storing ecosystems healthy. As a global community it is time to invest in the future of amphibians, which is an investment in the future of our planet.”
STATE OF THE WORLD’S AMPHIBIANS
The Second Global Amphibian Assessment
Amphibians are incredibly diverse, occur in nearly every habitat, and span almost the entire planet. Many species have narrow habitat preferences and small distributions, often making them especially sensitive to the rapid environmental changes taking place worldwide. Amphibian populations can provide valuable insights into the overall health and ecological balance of an ecosystem.
Through the second Global Amphibian Assessment (GAA2), more than a decade of research on amphibians by over 1,000 experts has been compiled to assess the extinction risk of 8,011 species worldwide. The GAA2 follows on from the first GAA, completed in 2004, which illuminated the unfolding amphibian extinction crisis and established a baseline for monitoring trends and measuring conservation impact. Now, the GAA2 reveals that the conservation status of the world’s amphibians continues to deteriorate.
We now know that 41% of amphibians are globally threatened with extinction, making them the most threatened vertebrate group. Salamanders are particularly at risk, with 3 out of every 5 species threatened with extinction. The number of amphibian extinctions could be as high as 222, when considering the 37 confirmed extinctions and an additional 185 species with no known surviving population.
Habitat loss remains the most common threat to amphibians, affecting 93% of threatened species. Agricultural expansion continues to be the main cause of habitat loss and degradation, followed by timber and plant harvesting, and infrastructure development. Amphibians are also threatened by disease in many parts of the world. Over the past few decades, chytridiomycosis has had a devastating impact on amphibian populations, and the emergence of a new fungal pathogen in Europe that targets salamanders has raised fears of another epizootic. The effects of climate change are emerging as a concerning threat as amphibians are particularly sensitive to changes in their environment.
Amphibian species are not evenly distributed across the globe. They are predominantly clustered in tropical montane humid forests as well as on tropical islands. Islands with high endemism and extensive habitat loss, such as those in the Caribbean, dominate the list of 15 countries or territories with an extraordinarily high percentage of threatened species. The Neotropics, home to almost half of the world’s amphibians, is also the most highly threatened realm, with 48% of species at risk of extinction. Other large concentrations of threatened amphibians are found in western Cameroon and eastern Nigeria, the Eastern Arc Mountains of Tanzania, Madagascar, the Western Ghats of India, Sri Lanka, and central and southern China.
Conservation needs to be massively scaled-up. Since 1980, the extinction risk of 63 species has been reduced due to conservation interventions, proving that conservation works. We must build on this momentum and significantly scale-up investment in amphibian conservation if we are to stop and reverse declines. Drawing on the results of the GAA2, this report provides guidance for conservation by identifying landscapes with disproportionately high numbers of threatened species, as well as the most highly threatened amphibian genera. It also highlights the need to protect globally important sites for amphibians, and the urgent necessity to better understand and find solutions to the problems that disease and climate change present. It is imperative that we now use this information to effectively conserve and restore the world’s amphibians.