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The Sixth Extinction: An Unnatural History
The Sixth Extinction: An Unnatural History
Elizabeth Kolbert
Picador, 2015
336 pp., 18.00

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Jonathan Hiskes

Planet of the Rats

Extinction in progress.

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The pages of Elizabeth Kolbert's The Sixth Extinction: An Unnatural History teem with extraordinary animals that no longer exist. We meet ancient beavers the size of grizzly bears, great auks that waddled like penguins on North Atlantic shores until they were hunted into extinction, and mastodons, hulking cousins of elephants with teeth the size of bricks.

We also meet animals that may well become extinct in our lifetime, such as Sumatran rhinos, hunted for their horns. These shy, solitary creatures perpetuate their species (for now, at least) through sex lives that baffle the zoo conservationists who have tried to breed them without success. Fewer than 100 Sumatran rhinos are believed to remain in the world.

To me, though, the saddest creatures in Kolbert's book are the ones extinguished before we ever discover them. In the Panamanian rainforest, a fungus introduced by humans decimated the population of golden frogs, a revered national symbol. Conservationists constructed a "frog hotel" in a desperate attempt to save the species, even though they have no plan for how to reintroduce them to the wild. In the course of filling their modern-day ark, they discovered that the fungus has eliminated other frog species never before discovered. "We are losing all these amphibians before we even know they exist," a Panamanian conservationist told Kolbert.

It strikes me as profoundly wrong to extinguish creatures before studying or even naming them. Giving names to "every beast of the field, and every fowl of the air" is one of the very first tasks that God assigns to human beings in Genesis. We fail this duty each time a species passes unstudied into oblivion.

But Kolbert's task here is reportage, not moralizing. A New Yorker staff writer and author of Field Notes from a Catastrophe: Man, Nature, and Climate Change, she excels as a cool-headed reporter, drawing on biologists, geologists, and historians of science to reveal the impact of 7 billion people on the rest of the planet's species. She travels the globe to track these effects, collecting fossils in the Scottish uplands, visiting clear-cut rainforests, diving off the Great Barrier Reef, spelunking in New York, and watching an attempted insemination of Suci, a Sumatran rhino, at the Cincinnati Zoo.

Each chapter of The Sixth Extinction centers on a particular species or location, but the ultimate focus is broader: not individual extinctions (and near-extinctions), but patterns of extinction. The last half-billion years, we know from fossil records, have brought five mass extinctions. These are periods in which the rate of species loss spikes to a level high enough to change the character of the planet.

Paleontologists have discovered we are in the midst of the sixth mass extinction, likely to be the most severe since the asteroid crash that killed off the dinosaurs at the end of the Cretaceous period. The cause this time is us. Kolbert quotes a paleontologist who uses a tree-of-life metaphor: "During a mass extinction, vast swathes of the tree are cut short, as if attacked by crazed, axe-wielding madmen."

The reason is not just global warming, although chemically altering the atmosphere is no small part of humanity's impact. Our species' impact starts with our sheer restlessness. Beginning somewhere in eastern Africa, we have managed to cross oceans to spread ourselves to most corners of the globe, carrying with us other organisms. That shuffling has radically affected native creatures evolved to live within a particular ecosystem with particular neighbors.

"Without being loaded by someone onto a boat or plane, it would have been impossible for a frog carrying Bd [the deadly fungus that has virtually wiped out the golden frog] to get from Africa to Australia or from North America to Europe," Kolbert writes. "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."

In a single summer tourist season, visitors brought more than 70,000 seeds to Antarctica. Rats, Kolbert notes, are particularly adept at hitching rides with us as we travel, and they have left their bones scattered on islands so remote that humans never stayed to settle them. They may be the creatures best suited to adapt as planetary conditions change from the ones which allowed humanity's population to explode. "Rats have followed humans to just about every corner of the globe," Kolbert writes, "and it is [one geologist's] professional opinion that one day they will take over the earth." Good times, huh?

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