The Sixth Extinction: An Unnatural History

by Elizabeth Kolbert

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Today, amphibians enjoy the dubious distinction of being the world’s most endangered class of animals; it’s been calculated that the group’s extinction rate could be as much as forty-five thousand times higher than the background rate. But extinction rates among many other groups are approaching amphibian levels. It is estimated that one-third of all reef-building corals, a third of all freshwater mollusks, a third of sharks and rays, a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are headed toward oblivion.

One theory has it that Bd was moved around the globe with shipments of African clawed frogs, which were used in the nineteen-fifties and sixties in pregnancy tests. (Female African clawed frogs, when injected with the urine of a pregnant woman, lay eggs within a few hours.)

This sort of intercontinental reshuffling, which nowadays we find totally unremarkable, is probably unprecedented in the three-and-a-half-billion-year history of life.

One of the Americans, Chris Bednarski, from the Houston Zoo, warned me to avoid the soldier ants, which will leave their jaws in your shin even after they’re dead.

San Jose Cochran frogs are part of a larger family known as “glass frogs,” so named because their translucent skin reveals the outline of their internal organs.

Everything (and everyone) alive today is descended from an organism that somehow survived the impact. But it does not follow from this that they (or we) are any better adapted. In times of extreme stress, the whole concept of fitness, at least in a Darwinian sense, loses its meaning: how could a creature be adapted, either well or ill, for conditions it has never before encountered in its entire evolutionary history? At

SINCE the start of the industrial revolution, humans have burned through enough fossil fuels—coal, oil, and natural gas—to add some 365 billion metric tons of carbon to the atmosphere. Deforestation has contributed another 180 billion tons.

Each year, we throw up another nine billion tons or so, an amount that’s been increasing by as much as six percent annually.

It is expected that such an increase will produce an eventual average global temperature rise of between three and a half and seven degrees Fahrenheit, and this will, in turn, trigger a variety of world-altering events, including the disappearance of most remaining glaciers, the inundation of low-lying islands and coastal cities, and the melting of the Arctic ice cap. But this is only half the story.

Gases from the atmosphere get absorbed by the ocean and gases dissolved in the ocean are released into the atmosphere. When the two are in equilibrium, roughly the same quantities are being dissolved as are being released. Change the atmosphere’s composition, as we have done, and the exchange becomes lopsided: more carbon dioxide enters the water than comes back out.

Assuming that humans continue to burn fossil fuels, the oceans will continue to absorb carbon dioxide and will become increasingly acidified.

“Unfortunately, the biggest tipping point, the one at which the ecosystem starts to crash, is mean pH 7.8, which is what we’re expecting to happen by 2100,”

“Some highly tolerant organisms will become more abundant, but overall diversity will be lost. This is what has happened in all these times of major mass extinction.”

Ocean acidification is sometimes referred to as global warming’s “equally evil twin.”

Ocean acidification played a role in at least two of the Big Five extinctions (the end-Permian and the end-Triassic) and quite possibly it was a major factor in a third (the end-Cretaceous).

By burning through coal and oil deposits, humans are putting carbon back into the air that has been sequestered for tens—in most cases hundreds—of millions of years. In the process, we are running geologic history not only in reverse but at warp speed.

“is likely to leave a legacy of the Anthropocene as one of the most notable, if not cataclysmic events in the history of our planet.”

in Science in 2008, found a third of them to be in danger of extinction, largely as a result of rising ocean temperatures.

Obviously, any animal that depends on the ice—ringed seals, say, or polar bears—is going to be hard-pressed as it melts away. But global warming is going to have just as great an impact—indeed, according to Silman, an even greater impact—in the tropics.

(Baking soda, or some other alkaline substance, is necessary for coca to have its pharmaceutical effect.)

he found that global warming was driving the average genus up the mountain at a rate of eight feet per year.

Warming today is taking place at least ten times faster than it did at the end of the last glaciation, and at the end of all those glaciations that preceded it. To keep up, organisms will have to migrate, or otherwise adapt, at least ten times more quickly.

“Look around you. Kill half of what you see. Or if you’re feeling generous, just kill about a quarter of what you see. That’s what we could be talking about.”

“Climate Change Could Drive a Million of the World’s Species to Extinction,” the BBC declared. “By 2050 Warming to Doom a Million Species” is how the headline in National Geographic put it.

It looks only as far as 2050 when, under any remotely plausible scenario, warming will continue far beyond that. It applies the species-area relationship to a new, and therefore untested, set of conditions.

Meanwhile, for two and a half million years, there’s been no advantage in being able to deal with extra heat, since temperatures never got much warmer than they are right now.

in the tropical rainforests, this means that something like five thousand species are being lost each year. This comes to roughly fourteen species a day, or one every hundred minutes.

One of the defining features of the Anthropocene is that the world is changing in ways that compel species to move, and another is that it’s changing in ways that create barriers—roads, clear-cuts, cities—that prevent them from doing so.

That ant bird looks an awful lot like a shih tzu or is it just me

Bats are what are known as “true hibernators”;

“It was like the Bush administration. And, like the Bush administration, it just wouldn’t go away.”

The white powder is now known to be a cold-loving fungus—what’s known as a psychrophile—that was accidentally imported to the U.S., probably from Europe. When it was first isolated, the fungus, from the genus Geomyces, had no name. For its effect on the bats it was dubbed Geomyces destructans.

To dispose of the toads humanely, the council instructs children to “cool them in a fridge for 12 hours” and then place them “in a freezer for another 12 hours.”

Though it might be nice to imagine there once was a time when man lived in harmony with nature, it’s not clear that he ever really did.

With the capacity to represent the world in signs and symbols comes the capacity to change it, which, as it happens, is also the capacity to destroy it. A tiny set of genetic variations divides us from the Neanderthals, but that has made all the difference.

“Right now we are in the midst of the Sixth Extinction, this time caused solely by humanity’s transformation of the ecological landscape.”

One possibility—the possibility implied by the Hall of Biodiversity—is that we, too, will eventually be undone by our “transformation of the ecological landscape.”

“Homo sapiens might not only be the agent of the sixth extinction, but also risks being one of its victims.”

Stanford ecologist Paul Ehrlich: IN PUSHING OTHER SPECIES TO EXTINCTION, HUMANITY IS BUSY SAWING OFF THE LIMB ON WHICH IT PERCHES.

There are serious scientists who argue, for instance, that should global warming become too grave a threat, we can counteract it by reengineering the atmosphere. Some schemes involve scattering sulfates into the stratosphere to reflect sunlight back out to space; others involve shooting water droplets over the Pacific to brighten clouds. If none of this works and things really go south, there are those who maintain people will still be OK; we’ll simply decamp to other planets.

The Sixth Extinction will continue to determine the course of life long after everything people have written and painted and built has been ground into dust and giant rats have—or have not—inherited the earth.