Two of five amphibians threatened with extinction; climate change emerging as primary driver: Study

Climate change is the new driver pushing the amphibian population towards extinction, a new study showed. 

Climate change was the primary threat for only 1 per cent of amphibian species whose conservation status in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species worsened between 1980 and 2004. But since then, it has emerged as the primary threat for 39 per cent species, the report published in the journal Nature showed. 

The study Ongoing declines for the world’s amphibians in the face of emerging threats indicated that after diseases, climate change and habitat loss were the emerging factor that is threatening vertebrates such as frogs, caecilians and salamanders. 

The second global assessment was based on analysing extinction risk of over 8,000 amphibian species in the world. This included the 2,286 species studied for the first time based on the IUCN Red List of threatened species. 

The findings showed that two of every five amphibians were threatened with extinction.

Amphibians were also found to be particularly vulnerable, with 40.7 per cent of the species being globally threatened – highest for any species. The status of amphibians, according to the latest Red List, continues to be deteriorating globally, especially for salamanders of which three of every five species are threatened.

The authors of the report, in a press statement, expressed concern about a deadly salamander fungus that has been found in Asia and Europe, called Batrachochytrium salamandrivorans, entering the Americas.

“Disease and habitat loss drove 91 per cent of status deteriorations between 1980 and 2004. Ongoing and projected climate change effects are now of increasing concern, driving 39 per cent of status deteriorations since 2004, followed by habitat loss amounting to 37 per cent,” it stated.

According to the paper, the 2004 baseline side found habitat loss, degradation and over-exploitation as major threats causing deterioration to more than half the species between 1980 and 2004. It said that 48 per cent were classified as enigmatic decline species and further studies showed that diseases such as chytridiomycosis, caused by Batrachochytrium dendrobatidis, were mainly responsible for many enigmatic declines.

The highest concentration of threatened species were mapped to be located in India’s Western Ghats, Sri Lanka, Madagascar, Caribbean islands, tropical Andes, Mesoamerica and the mountains and forests of western Cameroon and eastern Nigeria.

Other geographic locations of high concentrations included the Atlantic Forest biome of southern Brazil, central and southern China and the southern Annamite Mountains of Vietnam.

The second most threatened group of vertebrates included cycads that faced 69 per cent threat; sharks and rays faced 37.4 per cent threat, conifers faced 34 per cent, reef-building corals 33.4 per cent, mammals 26.5 per cent and reptiles 21.4 per cent.

Dragonflies, birds and cone snails faced 16 per cent, 12.9 per cent and 6.5 per cent threat respectively. 

The number of species extinct may be higher than estimated, the researchers noted. “Many species missing for decades are categorised as Critically Endangered and tagged as Possibly Extinct [CR (PE)]. For 1980, 24 amphibians were categorised as CR (PE), for 2004 this increased to 162, with another 23 added for 2022.”

If the classification is assumed to be true, the number of known amphibian extinctions could extend to as many as 222 in the past 150 years, according to the report.

In the latest study, 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.

The researchers documented major threats driving amphibians towards extinction due to habitat loss and degradation. The biggest threat was assessed to be agriculture contributing to 77 per cent, timber and plant harvesting impacting 53 per cent of them and infrastructure development at 40 per cent. Habitat destruction and degradation affected 93 per cent of all threatened amphibian species.

The emerging driver was noticed to be climate change and diseases, impacting 29 per cent amphibian species each.

The researchers observed that between 2004 and 2022, critical threats such as climate change contributed as 39 per cent primary threat to deteriorating their status and pushing 300 amphibians close to extinction. The numbers were likely to increase with data and projections in future revealing how the species respond to climate change. 

In a press statement, M Firoz Ahmed, scientist and wildlife biologist in Assam who contributed to the study said, “Northeast India and the Eastern Himalayan Biodiversity Hotspot are very rich with amphibian diversity. As many as 147 (of 426 across India) species are known to occur within the region, including Sikkim, as found during the Global Amphibian Assessment 2022 carried out across the world.” 

The previous assessment was conducted in 2004, he noted. “The (latest) assessment found that 23 species are threatened with extinction in northeast India, of which seven were Critically Endangered and 10 Endangered. Further, 27 per cent of the species (40) were poorly known and lacked sufficient information to assess, indicating the need for basic research on the least studied groups of animals.”

The press statement showed that Indian scientists studied 426 species, of which 136 were in the threatened category, while 20 per cent were data deficient, highlighting the need for research. 

The assessment also noted that 120 species improved their Red List status since 1980, of which 63 species improved their status directly due to conservation action such as habitat protection and management from countries like Costa Rica and Sabah in Malaysia and the Western Ghats in India.

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