The Sixth Extinction

Elizabeth Kolbert

Publisher Holt

Very, very occasionally in the distant past, the planet has undergone change so wrenching that the diversity of life has plummeted. Five of these ancient events were catastrophic enough that they’re put in their own category: the so-called Big Five. In what seems like a fantastic coincidence, but is probably no coincidence at all, the history of these events is recovered just as people come to realize that they are causing another one.

                          from  The Sixth Extinction


 The future of Earth: There's good news and bad news

This is probably not going to be the feel-good book of the year.

In 2008, an article appeared in the Proceedings of the National Academy of Sciences titled, “Are We in the Midst of the Sixth Extinction? A View from the World of Amphibians.”

Over the past half billion years, there have been five great extinctions during which “the planet has undergone change so wrenching that the diversity of life has plummeted.”

The first great extinction took place during the Ordovician period, about 450 million years ago, when life on this planet was still basically a watery affair. The greatest extinction event happened about 250 million years ago at the end of the Permian period, when life on earth came close to being snuffed out altogether. The most recent mass extinction occurred around 60 million years ago in the Cretaceous period, when a huge asteroid struck the earth; the resulting “nuclear winter” killed all large life forms, most notably the dinosaurs.

The paper’s authors, David Wake of the University of California-Berkeley and Vance Vredenburg of San Francisco State argued that, based on the current extinction rate of amphibians around the world, we are now in the midst of an event of similar catastrophic magnitude. This sixth extinction is of particular interest to humans because (1) unlike the others, we are living during this event, and (2) we are causing it.

Elizabeth Kolbert, science writer for The New Yorker and author of Field Notes from a Catastrophe (2006) about the impact of climate change, set out to investigate this idea. She traveled to various parts of the world, witnessing first-hand the loss of our “biodiversity.”

The scientific data is staggering: “It is estimated that one-third of all reef-building corals, a third of all fresh-water 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.”

This current extinction event probably began around 12,000 years ago (which is like only this morning in geologic time), and the main agent is modern humans, who have continuously spread over the planet and altered the ecosphere of whichever area they have inhabited, in much the same way as an invasive species.

It is a little unsettling to think of humans as an invasive species, perhaps even capable of killing its host. Kolbert quotes Stanford’s ecologist Paul Ehrlich: “In pushing other species to extinction, humanity is sawing off the limb on which it perches.”

The good news is that, based on past extinctions, the planet will survive and life will go on in some form; the bad news is that we humans may not be part of it.


This review first appeared in The Columbia River Reader (April 15-May14, 2014.) Reprinted with permission.