Cover image of a book about the Sixth Extinction

You probably know that you and I—actually, all of us collectively, homo sapiens the species—are responsible for a truly alarming reduction in the number of other species on Planet Earth. But apart from occasional stories in the media about endangered polar bears and black rhinos and the like, you may feel, as I do, that it’s tough to get terribly excited. As it turns out, only a handful of these disappearing species are “charismatic” large animals. In fact, nearly all of them are small, many of them vanishingly so; they’re plants as well as animals, few of them even with names, and they’re hidden away in tropical forests. From a scientific perspective, that’s no less serious. But the PR angle is tough to find.

A brilliant new book

In an outstanding new book, The Sixth ExtinctionElizabeth Kolbert tackles this challenge with considerable success. Kolbert, a science journalist on the staff of The New Yorker, spoke about the mass extinction now underway in an illuminating presentation last Wednesday to a large and attentive audience at the Hillside Club, under the auspices of Berkeley Arts & Letters. Her talk, like the book, was a sobering wake-up call.

The Sixth Extinction: An Unnatural History by Elizabeth Kolbert ★★★★★

Kolbert conducted extensive research for the book, including many thousands of miles of travel to visit scientists in research centers and in the field all across the globe. In The Sixth Extinction, and in a sketchier way during her presentation, she let us tag along, shaping each chapter around one of these trips, from Antarctica to the Amazon. The scientists she interviewed for the book include ecologists, biologists, geologists, paleontologists, geneticists, and authoritative figures in many other fields. She reports what she learned in straightforward, easily accessible language, resorting to a bare minimum of jargon. Though deeply disturbing, the book is a pleasure to read. (I wouldn’t expect anything less from a New Yorker staff writer.)

Humanity has been eliminating other species for a very long time

It transpires that we humans have been at this project of eliminating other species for a very long time — and we hold the dubious honor of being the only species to play an instrumental role in engineering such a large-scale killing spree. The five previous mass extinctions recorded by science over the past 630 million years were all the result of climate change.

As Kolbert emphasized in her remarks, there’s evidence going back more than 40,000 years to the arrival of homo sapiens in Australia, when we began systematically eliminating the enormous megafauna (gargantuan sloths, Brobdingnagian kangaroos, and so forth) that were common there in that era. Not that the animals they found were threatening them physically. Apparently, the new, human predators simply found the big beasts good to eat. Similar things happened in North America some 25,000 years later, when the original human settlers of what we now call the Western Hemisphere crossed the land bridge from Siberia and began hungrily devouring the mastodons and other huge animals they encountered. There don’t seem to have been any vegetarians among the forebears of today’s Native Americans.

Welcome to the Anthropocene Age

Fast-forward another few thousand years to the end of the last Ice Age roughly 12,000 years ago, shortly after which humans began farming and animal husbandry, and the extinction gained momentum. Then, about 500 years ago, the Columbian Exchange that came on the heels of early European exploration of the New World made matters worse by transferring innumerable plants and animals, diseases, and more aggressive farming techniques from one side of the Atlantic to the other. But it wasn’t until the advent of the Industrial Revolution that the pace began picking up steam (as it were). Then, the ingenuity that gave rise to large cities, railroads, and fast-growing human population ushered in what Kolbert refers to (following a number of eminent scientists) the Anthropocene Age. In that transition, we humans passed the point at which we were simply co-existing with other species and became the arbiters of their survival.

Today, in the full expression of the Anthropocene, we are advancing the extinction of the planet’s gloriously varied plant and animal kingdoms at a furious pace.

A black comedy of unintended consequences

Global warming is, of course, the most obvious means by which we’re engineering this dubious achievement. We’ve all heard a lot about that.

An equally if not even more serious consequence of the extraordinary amounts of carbon we’re pumping into the atmosphere every year is the dramatic acidification of the oceans. As you’re probably aware, one of the early results of this phenomenon is that the world’s coral reefs are beginning to die — and, as Kolbert reveals, coral reefs support “at least half a million and possibly as many as nine million species.” All the extra carbon dioxide we’ve released since 1800 has already made the oceans’ surface about thirty percent more acidic; at the current rate of carbon absorption, by the turn of the 22nd Century the oceanic ecosystem will start to crash. Kolbert reports a conversation with a British scientist who said, “in his understated British manner[,] ‘So, that is rather alarming.'” Indeed.

Many causes for the looming Sixth Extinction

These two factors — global warming and ocean acidification — are far from the only causes of the current species die-off. Invasive species, a reality since the Columbian Exchange, wreak havoc in ways both large and small. The habitat loss that comes with the expansion of cities, the building of roads and railroad tracks, and the desperation of poor farmers who turn to more and more marginal land for sustenance is another significant factor. Would I be wrong to assert that all these processes are, directly or indirectly, a consequence of the alarming growth of human population? After all, our total population today — 7.2 billion — is more than three times as great as it was when I was born in 1941!

Put it all together — the changing climate, the dying oceans, and the accelerating species die-off — and this is nothing less than the largest-scale ecological catastrophe since the disappearance of the dinosaurs sixty-six million years ago.

Will humanity survive?

This is the unspoken question that lurks in the background of The Sixth Extinction and, in fact, behind any discussion of the ultimate course of the changes we have set in motion on the only planet we inhabit. There is no scientific consensus on this question, but it’s one that eventually we may have to consider if the near-universal denial among the governments of the Earth continues to block effective action to slow the advance of global warming and the acidification of the oceans.

Given what we’ve seen so far, with tens of millions of dollars invested in campaigns to prevent action on climate change and willfully ignorant politicians insisting the problem is a scientific hoax, it’s difficult to be optimistic. If the planet does truly warm by an average of seven degrees Fahrenheit by 2100, how much of the land surface will remain inhabitable? And, with the oceans dead or dying, how could the human race manage to survive? (Forget that science fantasy about living underwater. If we go there, where will our food come from?)

Millions of years from now, when the rats or cockroaches have taken over the Earth, they might just erect a statue to that nameless (and apparently apocryphal) guy who cut down the last tree on Easter Island, thus securing the demise of his own people and ensuring that some other intelligent creature will inherit the planet. Because isn’t he the perfect symbol of our own mindless behavior as we humans continue to demolish the foundation on which our own lives rest?

For further reading

I’ve also reviewed Under a White Sky: The Nature of the Future by Elizabeth Kolbert (In the Anthropocene, the chickens come home to roost). It’s excellent, too.

This is one of the books I’ve included in my post, Gaining a global perspective on the world around us. It’s also one of the many Good books about climate change I’ve reviewed here.

It’s also one of 20 good nonfiction books about the future.

You’ll find an abundance of great nonfiction writing at Science explained in 10 excellent popular books. This one is included.

I also consider this book a lively contribution to the emerging field of Big History, so I’ve included it in my post, Great books on Big History: New perspectives on world history.

And you can always find my most popular reviews, and the most recent ones, plus a guide to this whole site, on the Home Page.