Endangered species of mammals - such as this gorilla - birds and amphibians occur in different geographical regions.

Credit: Thomas Lersch

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SYDNEY: Endangered mammals, birds and amphibians are apparently scattered across the globe, according to British researchers, a finding that contradicts current conservation models that assume they are clustered together.

"This means that even if a mountainous area has a real problem with endangered amphibians in its creeks and rivers, mammal and bird species might be flourishing," said Ian Owens of Imperial College London, co-author of the study.

Global conservation strategies have long assumed that endangered species from all groups are clustered in the same geographical areas. This new study, published in the British journal Nature, suggests this idea may be flawed - a finding that has big implications for conservation techniques.

Current conservation strategies often assume that different groups of animals show similar patterns in diversity: that patterns of distribution for threatened species in one group can act as an indicator for all groups. So-called 'silver bullet' strategies attempt to conserve regions with the highest number of endangered species by examining patterns in a single group.

This approach is flawed because of the different pressures that act on different groups, according to Owens. "Different factors entirely may affect mammals such as tigers which are under threat from poachers, and amphibians which are being diminished from diseases brought into their habitat by non-native fish," he said.

These new conservation insights were the result of the most detailed model of biodiversity ever produced. An international research team divided the terrestrial parts of the world into grid cells of about 100 km square. They then created three high-resolution maps showing the species present in each cell - one each for birds, mammals, and amphibians.

The study found that species richness across all groups was centred in the same regions - supporting the concept of biodiversity hotspots. However the trend broke down when only endangered species were considered.

According to the authors, the degree to which endangered species overlap in range varies, and the overlap "is especially low for the very rarest species".

"It's really important not to assume that there are simply a number of hotspots across the globe where every living thing … is endangered," said Owens. "The picture is far more complicated, with mammal, bird and amphibian numbers being threatened by different things, in different locations."

The authors stress caution when applying the findings to conservation, since the study examined only single species and not entire ecosystems. Additionally, the study focussed only on terrestrial habitats, ignoring endangered marine species.