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Ask the Dodo: The Blurry Line Between Endangered and Extinct Species

by Jennifer Billock

April 24, 2015

Approximately 1,000 species have gone extinct in the past 500 years. Well, make that approximately 1,000 minus one. Last month, a bird thought to have been extinct for 70 years resurfaced at an abandoned agricultural research station in Myanmar. Scientists there heard an unusual bird call and traced it back to a small brown bird called the Jerdon’s babbler, written out of birding guides as early as the 1940s.

The Jerdon’s babbler just made a comeback. Image by সৌরদীপ via Wikimedia Commons.

As of 2014, 3,879 animals and 2,655 plants are listed on the critically endangered species list and are likely to quickly disappear from the planet. But how can we know for certain that a creature is extinct?  Plenty of species are subject to threats from habitat damage, predators, and disease, and a lot of them are unlikely to experience regular contact with human beings. Prior to the 2000s, the International Union for the Conservation of Nature had a 50-year rule, stating that any animal that hadn’t been spotted in more than 50 years was considered extinct.

Today, the criteria for extinction are far more defined. Scientists must demonstrate repeated failed attempts to locate a species or any evidence of it in order for that label to apply. The law requires the Fish and Wildlife Service to survey the population status of each animal on the Endangered Species Act list at least once every five years, and extinctions can only be labeled as such after an intense review process from three independent experts and an opportunity for public comment.

The Lord Howe stick insect weathered supposed extinction on a single bush in the tropics for nearly 50 years. Image by Granitethighs via Wikimedia Commons.

But even this process isn’t perfect. As with Jerdon’s babbler, species previously thought to be extinct have a habit of resurrecting themselves. The New Guinea big-eared bat was thought to be extinct for about 120 years. The Clarion nightsnake, rediscovered in 2014, appeared on a remote island near Mexico. The Lord Howe stick insect weathered supposed extinction on a single bush in the tropics for nearly 50 years. And in perhaps the most spectacular display of an animal cheating death, the coelacanth—a 200-pound 6-foot fish from the dinosaur era—eluded detection for 65 million years until it resurfaced in 1938. In fact, research from 2010 shows that more than a third of the species feared extinct in the world have actually been spotted alive and well.

A preserved coelacanth and its pup. This 200-pound fish eluded detection for 65 million years. Image by Tim Evanson via Wikimedia Commons.

Does this mean that the world’s long-dead species are staging a comeback? Not exactly. Although pockets of species may still survive out of sight, scientists expect that 30 to 50 percent of the earth’s species will be wiped out by mid-century.

The “background rate” of extinction—otherwise known as the rate at which species naturally die off—is only one to five per year. But due to completely human factors like habitat destruction and global warming (which poses risks to 99 percent of the world’s currently endangered species), we are currently operating at 1,000 to 10,000 times the background rate, which science writer Elizabeth Kolbert says is catapulting us toward the world’s sixth mass extinction.

Get your goodbyes in now for the Western lowland gorilla. Image by Magnus Manske via Wikimedia Commons.

Some of Earth’s great species might not even make it to 2016. If we were to start preparing eulogies now, here’s what we will be saying goodbye to in the next year: the white rhino, Javan rhino, hawksbill turtle, south China tiger, Yangtze finless porpoise, western lowland gorilla, vaquita, Sumatran elephant, and mountain gorilla.

There is some hope, though. Protected areas have slowed extinction rates for certain species down by 20 percent, and new technologies like the iNaturalist app, which offers citizen scientists a way to report plant and animal sightings online, are making it easier for anyone to assist with conservation efforts. But there’s still a long way to go.

Illustration by Addison Eaton

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Ask the Dodo: The Blurry Line Between Endangered and Extinct Species