The world’s most respected database of endangered species is underestimating—sometimes severely—the risk of extinction to many animals around the world. That’s the conclusion of a new study, which finds that, by failing to incorporate new technologies like satellite and aerial imaging, the International Union for Conservation of Nature and Natural Resources’s (IUCN) Red List of Threatened Species has misclassified the threats to hundreds of animals. As a result, conservation groups may be missing numerous species at risk of disappearing.
The study’s overall approach is sound, says Stuart Butchart, head of science for BirdLife International in Cambridge, U.K., an organization tasked with tracking birds for IUCN. But he says the study’s authors misapplied their findings and mistakenly reclassified many of the animals—a charge the authors dispute.
The IUCN Red List, created in 1964, labels species on a scale ranging from “Least Concern” to “Extinct” with several gradients in between. The database relies upon studies by scientists and conservationists, as well as data from tens of thousands of volunteer and professional naturalists. IUCN officials plug those observations into an algorithm that considers factors such as habitat loss and population trends, and then ranks where the species fall on the Red List.
“It’s the international standard,” says Stuart Pimm, the senior investigator on the new study and a conservation biologist at Duke University in Durham, North Carolina. “And it’s not living up to its full potential.”
The problem, Pimm says, is that IUCN’s criteria for assessing species are outdated. The organization relies upon old maps drawn by experts for its habitat data, and it has not incorporated satellite and aerial imaging to better detect deforestation and encroaching human settlement. As a result, he says, the IUCN Red List’s assessments are missing subtle geographic features such as patchy deforestation and variations in elevation that can limit where species can live within a given range.
For the study, Pimm, along with study lead author Natalia Ocampo-Peñuela and colleagues, looked at 586 species of birds (the team is composed primarily of bird researchers) currently on the IUCN Red List from six bird-rich regions around the world, including the Western Andes of Colombia, Southeast Asia, and Brazil. Of those species, the list designates 108 as at risk for extinction. Pimm’s team analyzed the birds’ habitats using remote-sensing data on forest coverage and elevation. The researchers calculated how much viable habitat remains for each of the species, then reran IUCN’s risk assessment algorithms based on these new habitat estimates.
The bad news: 210 birds would be reclassified with a higher threat level—“threatened” or worse for the vast majority, the team reports today in Science Advances.
For example, the grey-winged cotinga is currently listed as “vulnerable” with a habitable range of some 3300 square kilometers in the forested mountains northeast of Rio de Janeiro, Brazil. The bird is only found at elevations between about 1200 and 1800 meters. Pimm’s team found that only about 100 square kilometers meet the bird’s habitat requirement. That would shift the bird’s threat level to “critically endangered.”
Though this study only analyzed birds, Pimm says the results should generalize to mammals and amphibians, as well.
Encouraging IUCN to adopt better mapping and remote sensing techniques is a laudable goal, writes Walter Jetz, an ecologist at Yale University, in an email. The main need, he adds, is for more habitat and biodiversity data to complement and expand on the IUCN Red List, rather than relying on the Red List as a singular authority on extinction risk.
Butchart says the researchers used the wrong parameters when recalculating the birds’ extinction risk and overestimated the species’ extinction risk. But the authors defend their approach.
As to the larger study’s suggestion that the Red List focus on viable habitat within a species’ range, Butchart writes that IUCN is planning to do just that in future iterations of the list.
*Update, 9 November, 3:51 p.m.: This story has been updated to clarify that Stuart Pimm is the lead investigator on the new study.