Researchers say tropical regions of richest diversity are most at risk of losing frogs, toads, newts and salamanders

If the current rapid extermination of animals, plants and other species really is the "sixth mass extinction", then it is the amphibian branch of the tree of life that is undergoing the most drastic pruning.

In research described as "terrifying" by an independent expert, scientists predict the future for frogs, toads, newts and salamanders is even more bleak than conservationists had realised.

Around half of amphibian species are in decline, while a third are already threatened with extinction. But scientists now predict that areas with the highest diversity of amphibian species will be under the most intense threat in the future.

And they warn that a three-pronged threat could also cause populations to decline faster than previously thought.

Like many creatures, amphibians have been hit hard by climate change and habitat loss. But they have also been decimated by the spread of the deadly fungal disease chytridiomycosis.

One in three of the world's amphibians are on the International Union for Conservation of Nature's red list of endangered species. These include the Malagasy rainbow frog that lives in the rocky forests of Madagascar. It has the ability to inflate itself when under attack and can climb vertical rock faces. Found in an area smaller than 100 square kilometres, it is a prime target for the pet trade.