Amphibian populations are declining worldwide, and their declines far exceed those of other animal groups: more than 30% of all species are listed as threatened according to the Red List of the International Union for the Conservation of Nature (IUCN).

Multiple factors threaten global amphibian diversity but the spatial distribution of these threats and their interactions are poorly known. A new study published in Nature with Dr. Christian Hof as lead author indicates that, worryingly, areas of greatest amphibian species richness are the areas subject to the greatest threat.

The research was led by Professor Carsten Rahbek, the Center for Macroecology, Evolution and Climate of the University of Copenhagen (Denmark) together with Professor Miguel B. Araujo, the Spanish Research Council (CSIC) at the National Museum of Natural Sciences, Madrid (Spain) and conducted in collaboration with Associate Professor Walter Jetz (Yale University, USA).

Among the most serious threats to amphibians are climate change, land-use change and the fungal disease chytridiomycosis. Christian Hof and colleagues assess the geographical distribution of these threats in relation to the global distribution of amphibians.

"Regions where climate and land-use change have the highest projected impact on amphibians tend to overlap", explains the researcher, "by contrast, the threat posed by the fungal disease shows little spatial overlap with the other two threats."

The researchers also find that the most species-rich areas in the world are more likely to be exposed to one or more threats than areas with low species richness: "Our study shows that more than two thirds of the global amphibian diversity hotspots will likely be strongly affected by at least one of the three threats considered", says Miguel Araujo from the Spanish Research Council (CSIC).

On the basis of the observed overlapping of risk factors, the authors suggest that risk assessments based on just one threat are likely to be over-optimistic.

"Our assessment shows that amphibian declines are likely to accelerate over the next decades, as multiple drivers of extinction could jeopardize their populations more than previous, mono-causal, assessments have suggested", says Carsten Rahbek from the University of Copenhagen.

Walter Jetz (Yale University) concludes: "With more than 30 per cent of all amphibian species already listed as threatened by IUCN and many rare species still being discovered every year, our results highlight the need for greater conservation research and action for this highly threatened group."