Bad news for frogs, amphibians and the like: Almost 41 percent of all known amphibian species worldwide are threatened with extinction, the salamanders being the most threatened. This was discovered by researchers who re-examined the current threat status of amphibians. They cite the destruction and deterioration of amphibian habitats as the main cause of the impending loss of species. But climate change is also playing an increasing role in the decline of amphibians - it has now overtaken fungal diseases as the cause, the researchers explain.
Species extinction is a global ecological problem that is progressing rapidly. More and more animal and plant species that were once common are now fighting for survival. Among the vertebrates, the diversity of amphibians is most at risk, as an extensive inventory from 2004 clearly showed. The decline in amphibians was primarily due to the loss of habitat, but also to epidemics that spread through the amphibian trade. Salamanders in particular, but also frogs, toads and newts are at risk from the deadly diseases that have been caused by the chytrid fungus (Batrachochytrium dendrobatidis) since the 1980s and by the salamander-eater fungus (Batrachochytrium salamandrivorans) for a good ten years.
A new study on amphibian biodiversity has now been published. It was commissioned by the International Union for Conservation of Nature (IUCN), which has published the international Red List of Endangered Animals since 1963. In the report, the over 100 scientists involved examined and evaluated the current global endangerment status in 2022 and the causes of endangerment of a total of 8,011 amphibian species. This assessment complements the knowledge of the first global amphibian assessment from 2004: It records 2,286 additional species and shows the changes in recent years.
How endangered are the amphibians?
The scientists found that two out of five of all amphibian species (around 41 percent) are now threatened with extinction, critically endangered or endangered. For comparison: For mammals it is 27 percent, for reptiles 21 percent and for birds 13 percent. In the case of salamanders it is even three out of five species. This makes them the most threatened group within the amphibians, followed by newts. Since 2004, various factors have led to the fact that more than 300 amphibians are now even more at risk of extinction than in the first survey.
Most threatened species live in the Caribbean islands, Mesoamerica, the tropical Andes, western Cameroon and eastern Nigeria, Madagascar, the Western Ghats of India and Sri Lanka, according to the new study. Four species have been proven extinct since 2004: the Chiriquí harlequin toad from Costa Rica, the sharp-snouted day frog from Australia, the frog species Craugastor myllomyllon and the false Jalpa stream salamander from Guatemala. A total of 37 amphibian species are now considered extinct. However, the assessment also found that 120 species have improved their status on the Red List since 1980 because their habitat has been protected.
What are the causes of the amphibian decline?
Since the first report, disease has been replaced as a major threat to most amphibians by climate change: For 39 percent of species that have become more threatened since 2004, climate change is the major threat, the new report says. Amphibians therefore react very sensitively to changes in their environment. “They cannot move far to escape the increase in extreme weather events or lack of rain caused by climate change,” says lead author Jennifer Luedtke from the IUCN.
However, the greatest threat to amphibians remains humans destroying and converting their habitats - particularly through agriculture, infrastructure development and other industries that pollute the environment. According to the study, this affects 93 percent of all threatened amphibian species worldwide, including salamanders, and 37 percent of the species that have been more threatened since 2004. These causes of threat would be exacerbated by the effects of climate change. “Increasing climate change will probably contribute more and more to endangering biodiversity in the future. “But this should not obscure the fact that ongoing habitat destruction is still by far the greatest threat to biodiversity,” emphasizes co-author Frank Glaw from the Munich State Zoological Collection.
How can you protect amphibians?
Amphibians are essential for ecological balance and also play an important role in medicine and pest control. In addition, their development is a warning about environmental changes that also affect us humans. Since the first amphibian assessment in 2004, many threatened species and their habitat have been protected. However, the authors of the new study urge further action. To protect amphibian diversity, it will be particularly important to preserve their habitats and create corridors between them through which the animals can spread.
“Protecting and restoring forests is crucial not only for protecting biological diversity, but also for combating climate change,” says Luedtke. The researchers hope that conservationists and politicians will use the information they have collected to improve global amphibian protection - including by acquiring additional resources for conservation measures to reverse the negative trend for amphibians.
Sources: IUCN, Museum of Natural History – Leibniz Institute for Evolution and Biodiversity Research, Bavarian State Natural Science Collections; Specialist article: Nature, doi: 10.1038/s41586-023-06578-4