Extinction Blind Spots
New research reveals that the mammals most at risk of disappearing in the near future may not appear threatened now. The reason, say the researchers, is that these species are disproportionately vulnerable to human disturbances.
“Many species currently considered safe could leapfrog other species on the extinction risk scale to become the most highly threatened in the next few decades,” say Marcel Cardillo of Imperial College London, U.K., and three coauthors in Proceedings of the National Academy of Sciences. This scenario is not hypothetical: the Guatemalan howler monkey (Alouatta pigra), for example, recently went from being considered of “least concern” to “endangered” in just three years.
Disturbance-sensitive animals tend to have ecological and biological traits such as small ranges, large bodies, and few young. Using new databases of these traits for nearly 4,000 terrestrial mammals, the researchers identified species that were inherently at risk to disturbances. The species were divided into nine groups, including carnivores, marsupials, and ungulates. Then the researchers compared the species’ inherent extinction risks to their current extinction risks, as documented by the World Conservation Union’s Red List. The difference between the two measures of extinction risk shows the likelihood of extinction as the human population grows—that is, the latent extinction risk. Finally, the researchers mapped the species’ distributions in grids of approximately 10,000 square kilometers and determined the average latent extinction risk of the species in each grid cell.
The highest-risk regions were concentrated in the extreme north—Canada, Alaska, Greenland, and the Siberian tundra—and in the islands north of Australia, from India’s Bay of Bengal to the southwest Pacific. Moreover, most of the highest-risk regions are overlooked by conventional ways of setting conservation priorities. There are 20 hotspots based on the top 10 percent of latent extinction risk, and these hardly overlap at all with the hotspots for the top 10 percent of biodiversity, endemics, or threatened species.
This doesn’t mean, however, that these other priority-setting measures should be abandoned. Rather, the researchers advocate adding latent extinction hotspots to the mix. “Identifying areas of highest latent risk offers the best chance to anticipate species losses before they begin and, thus, to implement effective preemptive conservation measures,” they say. Adopting this approach is urgent because many of the latent risk hotspots are in areas where the number of people is expected to rise extremely rapidly within the next decade.
By Robin Meadows