Modern conservation efforts focus on saving as much biodiversity as possible--and preventing living species from going the way of the dodo. Already, roughly 10 percent of the world's land falls inside of protected reserves. But new research highlights the mammals most at risk of disappearing in the near future even if they are unthreatened now, and the majority fall outside current conservation boundaries.

Biologist Marcel Cardillo of Imperial College London and his colleagues first estimated the overall risk of extinction a given mammal faced based on factors that led to the loss of other species in the past: a limited and specific geographic range, large size and relatively long periods of time needed to mature and reproduce. They then compared these factors to the animal's current risk of extinction as measured by the World Conservation Union and came up with a "latent extinction risk." The resulting list reveals mammals that are not threatened presently but could very quickly become threatened due to their biological extinction risk factors. In short, they could jump to the head of the line relatively rapidly.

"We can see this leapfrogging happening now--for example with the Guatemalan howler monkey, which was classified as being on the 'least concern' list in 2000 but which moved to the 'endangered' list in 2004 as it lost much of its forest habitat," Cardillo notes. "We hope conservationists will use our findings to preempt future species loss rather than concentrating solely on those species already under threat."

The arctic and tundra regions of North America and the islands stretching from the Indian Ocean to the South Pacific dominated the list, with New Guinea earning the dubious distinction of having the highest overall level of latent risk. The list includes a broad range of species, such as the North American reindeer, the musk ox, the Seychelles flying fox and Madagascar's brown lemur. Areas like Europe and Japan had the lowest threat, thanks to centuries of human development and relatively few surviving species at risk, according to the research, published in the current edition of Proceedings of the National Academy of Sciences.

Although these latent-risk hot spots are not necessarily the same as biodiversity hot spots, they may offer the chance to quash extinction pressures before they develop. "Latent-risk hot spots might provide cost-effective options for conservation," adds co-author Andy Purvis of Imperial College London. "They're places that are relatively intact and preventing damage is likely to be cheaper and more effective than trying to repair it."