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© Ana CarnavalHypsilboas faber, from Natividade de Serra, Brazil

Conservationists racing to catalogue and protect biodiversity before it vanishes could look to the past for guidance. A new study suggests they should focus on areas where climate has remained relatively stable over many thousands of years, allowing diversity to flourish.

Biologists have long known of the existence of biodiversity hotspots, regions of the Earth that are especially rich in species. But many of these hotspots - for example, the Atlantic forests of Brazil - are in remote tropical areas and have received relatively little study, leaving conservationists at a loss as to where they should direct their efforts.

"Once conservation dollars reach the Brazilian Atlantic forest, then what?" asks Thomas Brooks, vice president of Conservation International, a conservation group based in Arlington, Virginia. "There's no question that we need to know at a much higher resolution where to invest within the region."

Ana Carnaval, an evolutionary biologist at the University of California, Berkeley, and her colleagues tested a novel way to help refine this target.

Carnaval's team gathered palaeoclimatic data for the Atlantic forest hotspot and used that to map the likely geographic ranges of three species of tree frogs over the past 21,000 years.

Frog focus

They found that the central part of the Atlantic forest, in the area of Bahia, contains the largest area of habitat likely to have supported frogs continuously during that time. Areas further to the south, near Sao Paolo, had less stable conditions. The stable central region, they surmised, was likely to have maintained a more diverse flora and fauna than the area further south.

Sure enough, when the researchers analysed genetic samples from the frogs, they found greater diversity within the central region.

"We're assuming the frogs are telling a story that's applicable to the whole ecosystem," says Carnaval. Other data on birds and lizards also show unexpected diversity in the central Atlantic forest.

The results suggest that conservationists - who have until now centred most of their efforts on the southern Atlantic forest - may be missing the hottest part of this hotspot. "The central region deserves more attention," says Carnaval. Similar approaches may be useful in other poorly studied biodiversity hotspots around the world, she notes.

Journal reference: Science (DOI: link)