Species Extinction Happening 1,000 Times Faster Because of Humans?

 

On May 19, 2010, at Joint Base Balad, north of Baghdad in Iraq, someone brought U.S. service member Jonathan Trouern-Trend a frog in a plastic bottle. The brightly colored amphibian had been hiding out in an unlikely place: the latrine.

Many on base knew Trouern-Trend as "the guy to identify critters," he said. A lifetime nature lover, he was on his second tour of duty in Iraq as a sergeant.

Before releasing the frog into a nearby pond, Trouern-Trend uploaded a picture of it to the mobile app iNaturalist, which connects a worldwide community of people who report sightings of animals and plants online.

App users informed him that he'd found a lemon-yellow tree frog (Hyla savignyi)—and noted that scientists had never recorded one outside of Kurdistan (map). The species' known range had suddenly expanded.

The golden-headed or Cat Ba langur, shown here at the Endangered Primate Rescue Center in Vietnam's Cuc Phuong National Park, is a critically endangered primate. Earth's species are rapidly dwindling, due largely to habitat destruction and climate change.

 

A female (at left) and male endangered Schaus swallowtail, or island swallowtail, are seen at the McGuire Center for Lepidoptera & Biodiversity in Gainesville, Florida. Fewer than a hundred of the insects are left—on a single island in the Florida Keys.

Photograph by Joel Sartore, www.joelsartore.com

This kind of citizen science has exploded in recent years because of smartphones. Now, according to a new review of research about Earth's biodiversity, it's giving conservationists hope that new technology can slow extinctions. (See: "5 Surprising Drone Uses (Besides Amazon Delivery).")

That's good news, because according to a review published on May 29 in the journal Science, current extinction rates are up to a thousand times higher than they would be if people weren't in the picture.

Study leader Stuart Pimm, a conservation ecologist at Duke University and contributor to National Geographic's News Watch blog, and his colleagues analyzed various data sources—in particular the International Union for Conservation of Nature's Red List of Threatened Species, a global inventory of species—to produce the first major review of extinction data. (See: "20,000 Species Are Near Extinction: Is It Time to Rethink How We Decide Which to Save?")

Mobile apps, GIS satellite data, and online crowdsourcing, Pimm says, may be a partial antidote to the problem. Through these technologies, "we're mobilizing millions of people around the world, and we're on the cusp of learning very much more about where species are than we have ever known in the past." That's critical, he explains, because now "we know where the species are, we know where the threats are, and—even though the situation is very bleak—we are better able to manage things."

One of the two known surviving Rabb's fringe-limbed tree frogs, photographed at the Atlanta Botanical Garden, died in 2012. This critically endangered freshwater species from Panama may be extinct in the wild.

Photograph by Joel Sartore, www.joelsartore.com

Peter Crane, dean of Yale's School of Forestry and Environmental Studies, said by email that the new "paper does huge service in pulling together the latest thinking on species extinctions for very diverse groups of organisms."

Crane, who was not involved in the study, agreed that new technologies like remote sensing and more comprehensive databases "will not only improve the effectiveness of conservation investments, but will also strengthen monitoring of change in species-level biodiversity through time."

How Many Out There?

Calculating extinction rates can be difficult, in part because no one knows exactly how many species there are. Scientists have identified at least 1.9 million animal species, and possibly millions more have yet to be named. And according to the study, at least 450,000 plant species likely exist.

Pimm says conservationists can calculate the extinction rate of the known species by keeping track of how many die out each year.

The technique is similar to that used to figure out a country's death rate: track the number of people who die in a given population each year, scaled to that population. Mortality rates are usually calculated as the number of deaths per thousand people per year.

This critically endangered male blue-knobbed curassow was photographed at the Houston Zoo. Found in the wild only in Colombia, this species' population is estimated at fewer than a thousand.

Photograph by Joel Sartore, www.joelsartore.com

Applying the same statistical approach to extinction data revealed a rate of 100 to 1,000 species lost per million per year, mostly due to human-caused habitat destruction and climate change. (See: "7 Species Hit Hard by Climate Change—Including One That's Already Extinct.")

To calculate the rate of extinction before modern humans evolved, about 200,000 years ago, Pimm and his colleagues reviewed data from fossil records and noted when species disappeared, then used statistical modeling to fill in holes in the record. That analysis revealed that before humans evolved, less than a single species per million went extinct annually.

The study authors suspect that the extinction rate will only increase if trends continue—possibly resulting in what scientists call the sixth mass extinction in Earth's history. (Related: "The Sixth Extinction: A Conversation With Elizabeth Kolbert.")

Another conclusion of the study that can't be ignored, says Yale's Crane, is "that there remain huge gaps in knowledge. At least for the most diverse groups of organisms on Earth, the urgent need to clarify how many species there are, where they live, and how their populations are changing remains a key impediment."

Suci, a critically endangered Sumatran rhinoceros living at the Cincinnati Zoo, died this year. Intensive poaching has left fewer than 200 in the wild.

Photograph by Joel Sartore, www.joelsartore.com

People Power

To Jenny McGuire, a postdoctoral research scientist at the University of Washington's School of Environmental and Forest Sciences who wasn't involved in the study, the results aren't surprising.

Though some might quibble about the exact rate, she says, "in general scientists are in agreement that we're at a period of heightened extinction risk and rates, and that's been occurring nearly since humans have come onto the landscape."

A rare chucky madtom hangs on at Conservation Fisheries, a fish-breeding center in Knoxville, Tennessee. The species' population is unknown, but may include fewer than a hundred individuals.

Photograph by Joel Sartore, www.joelsartore.com

McGuire sees the new study as a "really excellent call to arms" for people to act to prevent more species from vanishing.

She says that people can vote for policies that lessen the impact of climate change, which is hitting the oceans particularly hard by raising the water's pH and dissolving the shells of many marine animals. People can also encourage their governments to connect one nature reserve to another.

Pimm says protected areas, the "frontline of conservation," have kept extinction rates of mammals, birds, and amphibians 20 percent lower than they would have been without refuges. Nearly 13 percent of Earth's land has been set aside, but only 2 percent of the ocean is part of a refuge.

 

A Florida panther named Lucy is shown at Tampa's Lowry Park Zoo. Only 160 of these southern panthers are left in the wild.

Photograph by Joel Sartore, www.joelsartore.com

Pimm and colleagues noted that global databases and crowdsourcing are helping to fill in blanks by tracking biodiversity outside of protected areas, where species tend to be less studied. (Also see "The Ethical Flap Over Birdsong Apps.")

And of course anyone can contribute by becoming a citizen scientist like Trouern-Trend, who said he's part of a "a niche of people who want to help out" by giving conservationists a snapshot of our world. "From fungus to birds to plants," he said, "it's all interesting to me."

Follow Christine Dell'Amore on Twitter and Google .

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