Amphibians, one of the most imperiled groups of life forms on the planet, have now officially reached 9,000 described species, according to a new research paper.
Amphibians reach 9,000 described species: a summary of ongoing trends, challenges, and opportunities by Sky T Button, Franco Andreone, and Amaël Borzée, notes that “this benchmark in described species represents a major milestone for both taxonomy and conservation, resulting from thousands of individual studies conducted by countless amphibian research teams”.
According to the authors, the number of recognised amphibian species has more than doubled within the past 40 years, and the number of annual new species descriptions appears to have peaked only recently, at 180 and 179 new species in 2017 and 2020, respectively.
Despite this landmark development, a substantial number of amphibian species (potentially ~6,000–7,000, although perhaps far greater or fewer) likely remain undescribed, say the authors. They add though that cumulative knowledge of 9,000 species is nonetheless highly significant and may plausibly represent more than half of all species.
The paper also breaks down how individual amphibian orders fare.
For instance, frogs, salamanders, and caecilians (which look worms or snakes) continue to be described at rapid rates, although with large differences in absolute numbers.
Anurans (frogs and toads) have been consistently observed as the most ‘speciose’ (biologically rich) amphibian group over hundreds of years, say the authors. They currently comprise ~88 per cent of all known amphibians and their dominance is unlikely to change, according to the paper.
Salamanders comprise ~9 per cent of all amphibians. A pattern is seen in the taxonomic evaluation of both orders, anurans and salamanders, in that both saw of relatively slow species descriptions for a long, historical period. This changed to a rapid spike in description rate near the end of the 20th century, possibly peaking in 2017-2020, note the authors.
“Notably, although the description rate for both groups has slowed slightly in the past four years, it is not yet possible to disentangle SAC-based explanations for this decline from impacts of the COVID 19 pandemic, which slowed overall scientific research immensely,” the paper reads. SAC stands for ‘species accumulation curve’.
Caecilians comprise only ~3 per cent of amphibians. Compared to anurans and salamanders, an even greater uncertainty exists for them, given the onerous nature of studying them (manual excavation), note the authors.
Increases in known caecilian richness have thus been strongly influenced by individual flurries in new research, following a less stable long-term pattern than for anurans or salamanders.
“Amongst amphibian species with geographic range data, the largest proportion (~37%) occur in South America, followed by Asia (~23%), North America (~17%), Africa (~15%), Oceania (~9%), and Europe (~1%; Frost 2025),” the paper states.
But the authors add that these raw percentages do not provide a complete picture, “considering that continents differ substantially in their size and current stage of biodiscovery”.
“After correcting (crudely) for area by dividing each continent’s proportion of globally known amphibians by its proportion of global (excluding Antarctica) land area (Briggs and Smithson, 1986), South America has by far the highest ratio (proportion of global amphibians ~2.8x higher than proportion of global land area), followed by Oceania (~1.6), North America (~0.9), Asia (~0.7), Africa (~0.7), and Europe (~0.2),” they estimate.
Interestingly, this means that Europe is by far the least amphibian-biodiverse continent (regardless of metric). Yet, it has received arguably the most research attention.
The paper concluded by estimating that amphibians of the planet would continue to be described till 2100.
“The description of 9,000 amphibian species is nothing short of remarkable considering the ongoing taxonomy funding crisis (Al-Asif and Nerurkar, 2024). However, while overall species description rates have potentially peaked in the past decade, subsequent declines should nonetheless be considered modest and inconclusive given additional research challenges posed by COVID-19 in these same years (D. Frost, pers. comm.). Regardless of the precise peak year for new species descriptions, any future plateau appears distant; 2025 has—as of mid-December—yielded >95% of the peak number of annual descriptions. Based on this continually high species description rate, it appears unlikely that fewer than ~3,000 additional amphibians will be described by 2100, with ~15,000–16,000 species appearing as a reasonable “best guess” (based both on empirical models and rule-of-thumb heuristics) for the total number of extant species.”
In a social media post, Gina Della Togna, Executive Director at Amphibian Survival Alliance, said the milestone was not just a celebration but also a call to action.
“Amphibians are the most threatened vertebrate group on Earth, yet they receive less than 2.8% of global conservation funding. At the same time, species discovery continues at an extraordinary pace — more than doubling in just 40 years — with strong evidence that thousands of amphibian species remain undescribed, many of them likely already at risk of extinction,” she wrote.
Togna concluded by saying that: “Every new species described brings wonder, but also responsibility. As the number of known amphibian species grows, so does the urgency to:
• Assess their conservation status
• Understand their threats
• Develop and fund targeted conservation actions
• Invest in taxonomy, capacity building, and regional expertise where biodiversity is highest and funding is lowest.”