Species are going extinct all over the world: Scientists believe that Earth is losing between 200 and 2,000 species every year. That number is squishy, partly because there are so many species for which they lack good data—particularly those living in the oceans, which are difficult to track but still critically important to ecosystems and livelihoods. Even the most comprehensive evaluation of extinction risk—the international Red List of Threatened Species—has only spotty data for many species around the globe.
A new study from University of Chicago scientists offers a tool to predict extinctions for hard-to-count species. Their method takes advantage of the fact that while some species are hard to monitor while alive, many of them leave extensive fossil records.
“Today’s extinction work tends to focus on animals like us—mammals and other vertebrates that live on land,” said Katie Collins, a postdoctoral researcher at the University of Chicago and first author on the paper. “But most things that live on the planet don’t have a backbone, and a huge part of the world’s biodiversity lives in the sea, where our picture is really incomplete. It’s much harder to get a handle on extinction there.”
Collins and David Jablonski, the William R. Kenan Jr. Distinguished Service Professor of Geophysical Sciences, along with a team of researchers at UChicago, the Smithsonian and the University of California, San Diego, wanted a way to estimate extinction risk for species that are short of directly measured data.
A key part of the puzzle came when they realized that the fossil record could help. Jablonski has been building a database of fossils of marine bivalves—creatures like scallops, mussels and oysters—for many years. That database allowed them to review the history of extinctions and develop a set of predictors about which species are most likely to go extinct.
“Fossils give you a bird’s-eye view of lineages. You can see the first and last occurrences for different species, and it can also tell you how often these lineages split into new species, how often they go extinct, and where they were when they did,” Collins said.