Tropical Birds Are in More Trouble Than We Thought

Scientists using remote sensing technology say we’ve been seriously underestimating the threats facing our planet’s birds. Writing in the journal Science Advances, the researchers say the standard wildlife risk assessment is “seriously outdated” and call for change.

The International Union for Conservation of Nature and Natural Resources (IUCN) Red List is the world’s go-to database for wildlife risk information. Federal and local government agencies rely on the list when making policy decisions, which means that the list’s accuracy could be a matter of life and death for the species involved.

“The Red List employs rigorously objective criteria, is transparent, and democratic in soliciting comments on species decisions,” Duke University scientist Stuart Pimm said in a statement. “That said, its methods are seriously outdated.”

Technology has advanced light-years in the 25 years since the list’s inception. Pimm, lead author Natalia Ocampo-Peñuela, and their colleagues hypothesized that using satellite data could provide a huge boost to the accuracy of wildlife risk assessments.

The team was especially interested in measuring animals’ areas of occupancy—a metric that provides a pretty reliable indication of a given species’ health or risk.

The researchers decided to focus their experiment on tropical birds in six wildlife hotspots around the world: the Atlantic forest of Brazil, Central America, the Western Andes of Colombia, Madagascar, Sumatra, and Southeast Asia. They then pulled satellite data on the known habitat areas of 586 native birds species, of which 108 were Red Listed as Vulnerable, Endangered, or Critically Endangered. The team combined maps of land use, national park designation, elevation, and forest cover to create a bigger picture of the worlds these birds inhabit.

Image Credit: Natalia Ocampo-Peñuela

That picture was not pretty. The data showed that 210 of the 586 species were in more danger than the Red List recognized, including 189 that are currently categorized as Nonthreatened. Ocampo-Peñuela says some of the discrepancy may come from focusing on habitat size and failing to consider other geographic details like elevation and humidity.

“Some bird species prefer forests at mid-elevations, while others inhabit moist lowland forests,” she said. “Knowing how much of this preferred habitat remains—and how much of it has been destroyed or degraded—is vital for accurately assessing extinction risks,” she said, “especially for species that have small geographical ranges to begin with.”

The researchers offer a “modest” addition to each Red List citation: a single sentence that lays out a species’ area of occurrence and spells out how much of that area is within the species’ preferred elevation, how much of it is natural habitat, and how much is currently protected.

“With better data, we can make better decisions,” Ocampo-Peñuela said, “and have a greater chance of saving species and protecting the places that matter.”