Are We Causing the Next Mass Extinction?

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A school of manini fish pass over a coral reef at Hanauma Bay on January 15, 2005 in Honolulu, Hawaii. Many coral reefs are dying from water pollution.

Forty-four years ago on April 22, 1970, demonstrations were set off around the country as Senator Gaylord Nelson established the first Earth Day. There was an outpouring of citizen concern, along with growing support from Congress, which led President Richard Nixon to sign an executive order that established the Environmental Protection Agency in December 1970.

Since then, environmental protection has become a political issue with deep partisanship on both sides—even as the most recent United Nations report on climate change warns of dire food shortages and other national security threats for countries across the globe.

See Also: U.N. Panel: Humans to Blame for Climate Change

Climate change has also diminished biodiversity, a problem with potentially serious consequences for every species.

Elizabeth Kolbert, staff writer for The New Yorker and author of "The Sixth Extinction: An Unnatural History," says we may be on the brink of another mass extinction. She defines mass extinction as a moment of time when the diversity on Earth, for one reason or another, plummets.

“Sixty-six million years ago, an asteroid plowed into planet earth and diversity on Earth plummeted,” she says. “That’s when we lost the dinosaurs among many other groups of organisms.”

There have been five mass extinctions throughout history, but Kolbert argues that the sixth mass extinction is different because it is being caused by humans.

“Right now unfortunately, extinction rates are very high, diversity is dropping very rapidly,” she says. “You sometimes hear scientists say that we are the asteroid in this context.”

When it comes to a mass extinction, entire ecosystems experience vast changes. Kolbert says we only know a tiny fraction of the species that occupy the planet, so it is difficult to understand how species truly interact. When the effects of taking a single organism out of an ecosystem are examined, however, Kolbert says massive effects and impacts can be seen.

“One of the groups that have been looked at most closely are large carnivores, which are really gone from most ecosystems, and those seem to have a very big cascading effect,” she says. “You get rid of those apex predators, and a lot of other things proliferate that then eat things; that then destroy habitats. So those effects really do ripple out through the landscape.”

All this may be happening too quickly—Kolbert says extinction is something that, over the course of the geological time spectrum, happens very rarely. According to her, one species of mammal should go extinct every several hundred years.

“If you’re a person who lives for 80 years, you should never see a mammal go extinct,” she says. “Now, we all know of mammals that have either gone extinct in our lifetime or are on the very, very edge of extinction. Unfortunately, in all of these extinctions we are a causal agent.”

Hawaii, which has been called “the extinction capital of the world,” is an interesting case in the study of extinction, says Kolbert. Since it was so isolated, its species were able to develop and thrive—until humans arrived.

“It's one of the most isolated places on the planet so one of the great mysteries on some level is how anything got there," says Kolbert. "Yet it did—it has wonderful birds, great flora and unique snails that you can find only in Hawaii. Animals mated, they radiated out, and they formed new species. It was missing many groups of animals like land mammals."

While the isolated chain of islands is still uniquely beautiful, Kolbert says that the arrival of other mammals—humans—disrupted the unique ecosystem in Hawaii.

"When people arrived and they brought rats and pigs and things like that, it really devastated the ecosystem,” she says. “That has just continued. We’ve brought more and more non-native species over and the native species were unprepared to deal with that.”

What will it take for people to stop seeing threatened species as statistics or small events in the course of history? Kolbert isn’t sure, but she says that time is running out. She says she was fortunate enough to spend time with the endangered Sumatran rhino, but not everyone will have that opportunity.

“If the future of the planet depends on everybody looking into the eyes of a Sumatran rhino then I’m afraid we’re in trouble, there are just too few of them left,” she says.

If things keep continuing on this path, Kolbert says our planet could look very different in the future.

“What’s happening right now is going to leave a mark that is, for all intents and purposes, permanent,” she says.

She says 100 million years from now, geologists will not only be able to see that many organisms went extinct, but they’ll also see the role we played in that extinction.

“We’re gonna see this huge emission of carbon, the carbon dioxide that we’re putting up into the air by burning coal and oil and natural gas,” she says. “That also leaves a record in the rock record.”