Getting close to the edge.

• Author: Rothschild, Matthew
• Position: The Sixth Extinction: An Unnatural History - Book review

The Sixth Extinction: An Unnatural History

By Elizabeth Kolbert

Henry Holt. 319 pages. $28.

This book is equal parts fascinating and horrifying. It's fascinating because it explains the way the biological world works. It's horrifying because it shows how ruinous our industrial footprint is on the globe.

It's not for nothing that Elizabeth Kolbert is a staff writer for The New Yorker and the author, previously, of Field Notes from a Catastrophe. She knows her stuff, and she writes compellingly. Each of her thirteen chapters tells a story about a particular creature or habitat, and how the radical transformations that humans have wrought over the past 200 years have jeopardized it.

There is a chapter on the great auk, whose last specimen was found in Iceland. There is a chapter on the die-off in Panama of golden frogs. There is a chapter on the Great Barrier Reef. Kolbert ventures to all of these places and writes lucidly about them.

A lot of the history of science in this book was new to me, though it's very accessible. For instance, I didn't know that there were five big periods of extinctions on Earth, when catastrophic events took an enormous toll. (Yeah, I knew about the asteroid and the dinosaurs, but I didn't know about the others.)

The "sixth extinction" of the title refers to the present, and the catastrophe that humans are causing today.

"No creature has ever altered life on the planet" the way we have, Kolbert writes.

The first part of the book is a scientific mystery story, or several wrapped into one. For instance, up until the late eighteenth century, no one even knew that a species could vanish off the face of the Earth. Kolbert tells us that even someone as wise as Thomas Jefferson proclaimed: "Such is the economy of nature that no instance can be produced of her having permitted any one race of her animals to become extinct."

But there was a little problem. People were finding enormous bones, in Russia and in America, that didn't correspond to any living animal. Scientists bent over backwards to deny this or to suppose that those animals were still roaming around somewhere.

Kolbert introduces us to the French naturalist Georges Cuvier, who finally, in 1796, came up with the idea of especes perdues, or lost species. Cuvier made his leap by examining the molars of a mastodon found in upstate New York and a woolly mammoth found in Russia. He recognized that these were not elephant teeth, as had been assumed, but the teeth of two...