To protect species, experts must first classify their risk of extinction. Here's how the complicated process works.
By Douglas Main April 22, 2019 • 9 min readWhen it comes to wildlife conservation, miracles can happen. Take the American bald eagle, whose story you may be familiar with—or the Arabian oryx.
The eagle’s populations once dwindled to fewer than 500 nesting pairs, thanks in part to the widespread use of a pesticide called DDT, which thinned their eggs, as well as habitat loss and hunting. The U.S. banned DDT in 1972, and the bird was protected under the U.S. Endangered Species Act of 1973. Thirty four years later, bald eagles had recovered sufficiently to be removed from listing.
Then there’s the Arabian oryx, a medium-sized antelope with long, straight horns. It was hit even harder than the bald eagle, hunted (mostly for trophies) until it disappeared from its native range in the Middle East in the 1960s. The International Union for Conservation of Nature, which uses hard data to assess the conservation status of wildlife around the world, classified it then as “extinct in the wild.”
But the Arabian oryx held on in private reserves and zoos around the world. Reintroduction efforts began in 1980, and its numbers quickly grew. By 2011, there were more than 1,000 of them living in the wild, and the IUCN reclassified it as “vulnerable,” a significant improvement in its conservation status. It’s the first animal ever to revert to a “vulnerable” listing after being classified as extinct in the wild.
These two classification systems are both used for the protection of animals, but they are different—here’s how we decide which animals are endangered and threatened.
The IUCN periodically assesses every animal for which there is enough data to make an informed decision, explains Jon Paul Rodríguez, chair of the IUCN Species Survival Commission. This commission consists of more than 8,000 scientists in 162 countries.
The organization then decides where to place the animal on a spectrum, from worst to best: extinct, extinct in the wild, critically endangered, endangered, vulnerable, near threatened, and least concern.
Animals that are critically endangered, endangered, or vulnerable are all considered “threatened.” To make their decisions, the group considers data such as population size, number of breeding adults, geographic range, and the like. Rodriguez says that the group trains scientists intensively how to make these determinations. “It’s a fairly involved scientific exercise,” he says.
The IUCN is all about producing good science—it doesn’t, by itself, have legal force. “We produce data,” he says, “and then encourage society at large to consider those assessments in their decision-making.”
The Endangered Species Act, however, does have legal force in the U.S.
Signed into law in 1973, following public outcry over the decline of animals like the bald eagle, the act lists wildlife as “endangered” or “threatened.” Each of these designations provides a specific set of protections. When an animal is listed, habitat critical for its survival is demarcated, and there are some restrictions on what can be done in these areas. Listed animals also generally cannot be killed or harassed, unless somebody gets a special permit, and the penalty for doing so can involve fines and/or jail time.
The IUCN’s data is often used to make Endangered Species Act listing decisions, but scientific information from other forums—such as NatureServe Explorer, a collection of population information on tens of thousands of American species—is used as well.
Nearly 1,700 species are listed under the act, and it has prevented the extinction of nearly 300 of those, according to a study published today in the journal PeerJ. While it remains one of the world’s most influential environmental laws, it has been controversial, with some arguing that too many species are listed without being recovered, while others posit the opposite. (Read more: How effective is the Endangered Species Act?)
