Global amphibian crisis: New study shows declines in 788 species over 40 years

Amphibians are among the most sensitive vertebrates on Earth – and among the most endangered. As early warning systems for the health of freshwater bodies and entire ecosystems, they respond particularly quickly to environmental change. According to the IUCN, 41% of all amphibian species worldwide are already considered threatened.

A new global analysis published in Nature Reviews Biodiversity now reveals the full scale of this crisis: Nearly 800 amphibian species have deteriorated in conservation status over the past 40 years. At the same time, the study makes clear that targeted conservation measures work when they are implemented consistently. The paradox: although amphibians account for around a quarter of all threatened vertebrates worldwide, they receive only 3.4% of global conservation funding.

Four decades of decline

The new analysis by Amaël Borzée, co-chair of the IUCN SSC Amphibian Specialist Group, and his international team is the first to systematically evaluate all changes in the IUCN threat status of amphibians since 1980. The results show a clear downward trend:

• 482 species deteriorated between 1980 and 2004,
• another 306 between 2004 and 2022.
• Over the same period, only 35 species improved (1980–2004) and
• 86 species (2004–2022).

That means the status of 788 species has worsened, while only 121 have improved – a ratio of six to one.

One of the few positive changes is McCranie’s robber frog: the species had been classified as extinct (EX) since 2004, but was reclassified in 2019 as Critically Endangered (Possibly Extinct) (CR(PE)), because it cannot be ruled out that a small remnant population survives somewhere.

37 species certainly extinct – 187 probably extinct

According to the study, 37 amphibian species are considered certainly extinct, including Wolterstorff’s newt (around 1979), the golden toad (1989) and the glossy poison frog (1992). The true number is likely higher: the study lists 185 species as Critically Endangered (Possibly Extinct); and according to the current 2025 IUCN Red List there are now even 187 species in the CR(PE) category.

These presumably lost species include, for example, the Australian yellow-spotted bell frog (Litoria castanea), last documented in 2012, and Rabbs’ fringe-limbed treefrog, whose last known individual, Toughie, died in human care in 2016.

Why amphibians are particularly threatened

Amphibians are considered the most sensitive group of vertebrates because they depend on two intact habitats at the same time: water for reproduction and larval development, and moist, shaded terrestrial habitats for adults. Many species also have extremely small ranges and depend on specific microhabitats, such as moist leaf litter or cool refuges for shedding skin and regulating body temperature.

The current study identifies four key drivers of the global amphibian decline:

1. Habitat loss – the strongest factor

With 2,684 affected species, habitat loss is the main cause of global population declines. It acts as a direct lethal factor, destroys microhabitats, and in the long term leads to genetic impoverishment and reduced adaptive capacity. The most important forms include:

• Deforestation and forest conversion: loss of shade, moisture, and structural complexity – vital for many frogs and salamanders.
• Agriculture (77% of species affected): monocultures, grazing, and irrigation dry out soils and fragment habitats.
• Modification of water bodies: channelization, dams, and drainage destroy breeding sites and alter microclimates.
• Infrastructure: roads, settlements, and energy facilities cut movement corridors and isolate populations.

Habitat loss hits amphibians particularly hard because they often move only short distances and have little ability to shift elsewhere. Even small-scale interventions can be enough to permanently wipe out local populations.

2. Climate change – a slow but massive stressor

According to the study, 845 species are directly affected by climate change. As ectothermic animals that use their skin for breathing and water uptake, amphibians respond extremely sensitively to changes in temperature and humidity.

Climate change operates on several levels:

• Heat stress: even small temperature increases can become life-threatening because amphibians have very narrow tolerance ranges.
• Desiccation: longer dry periods cause water loss, lower egg survival, and the failure of entire breeding cycles.
• Shifted rainy seasons: irregular precipitation disrupts courtship, migrations, and breeding sites.
• Extreme events: heatwaves, droughts, or heavy rainfall can be immediately lethal or destroy whole habitats.

Species with a narrow ecological niche are especially affected: tropical endemics, species strictly tied to specific microhabitats, and amphibians of mountain and high-altitude regions. High-mountain species in particular are specialized for cool, moist conditions, but above their habitats there is no “escape” left. They are therefore among the first to feel climatic change directly and are considered especially vulnerable in the analysis.

3. Diseases – a global crisis driven by chytrid fungi

According to the analysis, 880 amphibian species are directly affected by disease. Together with climate-related stress factors, this impacts nearly 29% of all threatened species.

At the center is the chytrid fungus Batrachochytrium dendrobatidis (Bd), complemented by the salamander fungus B. salamandrivorans (Bsal), which is particularly dangerous in Europe. Together they have caused one of the most severe disease crises ever documented in vertebrates.

The disease damages the skin, which in amphibians can lead to the collapse of osmoregulation, respiratory failure, and ultimately cardiac arrest. The restriction of many species to a small habitat promotes transmission of the disease. In addition, climate warming promotes fungal growth in certain regions. Due to the global wildlife trade, the pathogen has spread across multiple continents.

Since the 1990s, chytridiomycosis has been the main reason for listings in the highest threat categories (CR and CR(PE)). For example, the disease was detected in populations of the Chiriquí harlequin frog in 1993 and 1994; by 1996 the species was considered extinct.

A study by Scheele et al. (2019) showed that since the 1970s, populations of around 500 amphibian species have collapsed worldwide due to Bd, many of them irreversibly.

4. Pollution & invasive species – two underestimated drivers

Amphibians are extremely sensitive to chemical pollution because they absorb contaminants directly through their permeable skin. Pesticides, herbicides, industrial chemicals, fertilizers, and heavy metals can therefore enter their bodies directly and are often toxic even at low concentrations.

The consequences are diverse:

• disrupted hormone systems and impaired larval development,
• limb malformations,
• weakened immune systems and thus higher susceptibility to diseases such as Bd and Bsal.

Even though the current study does not give an exact number, it shows that chemical pollution is among the key additional stressors that further destabilize already weakened populations.

Invasive species also play a major role in the global amphibian decline. Introduced predatory fish, North American bullfrogs, as well as feral cats and rats prey on eggs, tadpoles, or adult animals and compete for food and habitat. Particularly problematic are fish introduced into originally fish-free mountain or forest waters – exactly the habitats many amphibians need for reproduction.

An example from the study shows how strongly such interventions can affect populations: in the Critically Endangered Spencer tree frog, the population collapsed because brown trout and rainbow trout ate almost all juveniles. Only after the invasive fish were actively removed did local populations recover – evidence that targeted measures against invasive species can have an immediate conservation impact.

Success stories: what effective conservation can achieve

The authors conclude: the global decline of amphibians is not an irreversible process. Where conservation measures are implemented consistently, populations demonstrably stabilize or recover. So far this affects only a small proportion of species, but the positive examples show that conservation works. India, Costa Rica, and Malaysia are highlighted as countries that have made major progress.

Melanophryniscus admirabilis – hydropower plant prevented

Melanophryniscus admirabilis, a species in the genus of red-belly toads, faced extinction when the construction of a hydropower plant was planned within its extremely small range in the Atlantic Forest of southern Brazil. The project would have flooded its entire habitat. Only through scientific documentation, political engagement, public pressure, and intervention by conservation organizations was the project stopped, creating the basis to implement targeted conservation measures for the first time. Without this intervention, the species would likely have disappeared.

Darwin’s frog: emergency program rescues populations

Rapid action has also shown its effectiveness in the South American Darwin’s frog, classified as Endangered (EN). When the chytrid fungus Bd was detected in one of its last remaining refuges, a rescue program was launched: subpopulations were removed and secured in intensive care to establish an ex-situ assurance colony. In parallel, efforts were made to contain the fungus in the wild. This emergency program may have prevented regional extinction.

More than 51% of all status improvements since 1980 are directly attributable to such targeted measures. Particularly successful are projects that

• remove invasive fish (e.g. for the Spencer tree frog),
• halt habitat loss,
• establish local protected areas,
• or regulate trade and use.

These examples make it clear: when conservation measures are implemented consistently, even highly threatened species can have a realistic chance of recovery.

Modern tools and international cooperation

The study authors emphasize: modern amphibian conservation no longer works through isolated projects. Diseases, climate change, and habitat loss do not stop at national borders; accordingly, it requires global strategies, combined with tools that clearly define priorities and direct scarce resources efficiently.

To enable this strategic work, international conservation now relies on several central instruments:

• Threatened Amphibian Landscapes (TAL)
  Identify regions where conservation measures are particularly effective and where investments achieve the greatest impact.
• Highly Threatened Genera
  Focus attention on entire genera with many threatened species – an approach that enables protection across whole evolutionary lineages.
• Key Biodiversity Areas (KBA)
  Globally recognized hotspots of biodiversity. They mark areas where protected areas deliver especially high benefits – often regions with many endemic amphibians.
• IUCN Red List Index
  Shows long-term trends: is the conservation status of a species group improving or worsening?
• IUCN Green Status of Species:
  Assesses not only the risk, but also a species’ recovery potential and progress through reintroductions or improved management.

Together, these tools form the strategic framework of modern conservation: they define priorities, enable efficient allocation of limited funds, and make progress measurable.

But as effective as these instruments are, without global cooperation they cannot realize their full potential. Local measures alone are not enough to halt the worldwide decline of amphibians.

A central umbrella is provided by the Kunming–Montreal Global Biodiversity Framework (KM-GBF). It defines global targets for conserving biodiversity and serves as a shared action framework for governments, research institutions, and NGOs.

For amphibians to have a real chance of recovery, it will take:

• internationally coordinated strategies,
• the exchange of knowledge,
• coordinated measures against diseases and invasive species,
• and global prioritization of available resources.

The successes achieved so far show that targeted conservation works. But only through consistent international cooperation can successful measures be scaled up and global trend reversals achieved.

Amphibians are in crisis, but not without hope

The new analysis makes one thing clear: amphibians are in crisis worldwide. Declines are occurring across all regions, and key threats such as climate change, disease, and habitat loss reinforce one another. This puts not only one group of animals under pressure, but also the stability of entire ecosystems at risk.

At the same time, the study shows that conservation works when it is implemented consistently. Wherever habitats have been protected, invasive species removed, or disease risks reduced, populations have recovered.

What is missing above all is the large-scale rollout of proven measures, sufficient funding, and international coordination. If these conditions are met, amphibians have a realistic chance of recovery.

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Sources

• Borzée, A., Prasad, V. K., Neam, K., et al. (2025). Conservation priorities for global amphibian biodiversity. Nature Reviews Biodiversity. https://doi.org/10.1038/s44358-025-00101-5
• Nitnaware, H. (2025, November 27). Amphibians see steep global decline: Study finds 788 species in decline over four decades. Down To Earth. https://www.downtoearth.org.in/wildlife-biodiversity/amphibians-see-steep-global-decline-study-finds-788-species-in-decline-over-four-decades
• Scheele, B. C., Pasmans, F., Skerratt, L. F., et al. (2019). Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity. Science, 363(6434), 1459–1463.
  https://doi.org/10.1126/science.aav0379
• Wong, C. (2023, October 4). These 10 amphibian species are giving us life. Re:wild.
  https://www.rewild.org/blog/these-10-amphibian-species-are-giving-us-life
• Wren, S. (2025, November 20). New global review finds conservation wins show a path forward. IUCN SSC Amphibian Specialist Group. https://www.iucn-amphibians.org/new-global-review-finds-conservation-wins-show-a-path-forward/