The Sixth Extinction: An Unnatural History

Book Written By Elizabeth Kolbert (Picador, $16, 319 pages, Paperback)
By Harvey Freedenberg

As this review is written in December 2015, 195 nations have just signed an historic agreement to limit greenhouse-gas emissions, with the goal of slowing what the overwhelming scientific consensus believes is the catastrophic pace of global warming. For anyone who doubts the reality that human activity is the chief driver of this looming disaster, I offer the evidence meticulously gathered and reported in Elizabeth Kolbert’s 2015 Pulitzer Prize-winning The Sixth Extinction: An Unnatural History. Kolbert’s book relates the globe-spanning story of how humankind, through its reliance on fossil fuels, is bringing on an age of mass extinction.

Kolbert, a staff writer for The New Yorker and author of Field Notes from a Catastrophe, has not written a polemic, but instead a work whose dominant tone is more sadness and dismay than alarm. This thorough, meticulously researched book combines field work with eclectic historical research. At one moment, Kolbert is trudging through the Amazon Rainforest to study the depopulation of bird species or snorkeling off Australia’s Great Barrier Reef to observe the increasingly rapid disappearance of coral reefs, decreasing by 50 percent in just the last 30 years. At another, she’s describing the work of men like Georges Cuvier, the naturalist credited with developing a theory of extinction in post-Revolutionary France, or Charles Darwin.

Each of The Sixth Extinction’s chapters is structured around the disappearance of a species that Kolbert calls “in some way emblematic,” moving from long-extinct creatures like the American mastodon, whose remains once populated an area around Cincinnati called Big Bone Lick, to more contemporary stories of extinction, like the golden frogs in Costa Rica.

Kolbert painstakingly marshals her evidence to argue that we are in the midst of the sixth great mass extinction, its most well-known predecessor the end-Cretaceous extinction that eliminated the dinosaurs some 66 million years ago. She’s careful to present the facts in a balanced way, offering the competing views of “catastrophists,” who pinpoint events like the asteroid that formed Mexico’s Chicxulub crater, and “uniformitarians,” who believe that extinctions occur at a slower pace. What this book emphatically does not do is pit scientists whose research confirms the reality of climate change and the impact we’re having on it against deniers in the kind of false debate that usually frames this issue in the mass media.

As Kolbert relates it, the burning of fossil fuels – adding some 365 billion metric tons of carbon into the atmosphere since the beginning of the industrial revolution – along with deforestation (another 180 billion tons), have raised the level of carbon dioxide in the atmosphere to a point higher than at any other time in the past 800,000 years. Describing a visit to the island of Castello Aragonese, in the Tyrrhenian Sea, Kolbert explains how this same carbon dioxide is increasing the acidity of the oceans. These phenomena combine to boost the temperature of our planet to dangerous levels. Even the most enthusiastic proponents of the new treaty recognize that it only goes part of the way toward stopping that increase short of the point where its effects become irreversible.

According to Kolbert, we have entered the Anthropocene, an age when “people have altered the composition of the atmosphere.”

How potentially dramatic is this human-caused extinction? “It is estimated,” Kolbert reports for starters, “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.”

Through the massive quantities of carbon industrialized and industrializing societies are discharging, Kolbert notes, “we are running geologic history not only in reverse but at warp speed.”

Kolbert is an elegant, at times almost poetic, writer when she is describing “villages made of mud brick and fields perched at improbable angles” on a mountainside in eastern Peru or stars “so bright they appeared to be straining out of the sky” above One Tree Island at the southernmost tip of the Great Barrier Reef. Even if your interest in science is only marginal, you’ll find yourself drawn into this story, both because of Kolbert’s ability to synthesize complex scientific concepts and her skill at presenting them in engaging and understandable terms.

Already, the Paris climate accord has sparked sharp debate between its advocates and those who argue it falls well short of fully addressing the role of humans in causing global warming. In a New Yorker blog post days after it was approved, Kolbert herself described it as “the most significant step forward since international climate negotiations began, more than two decades ago.”

Anyone interested in understanding this debate would do well to pick up The Sixth Extinction to be armed as well as an informed layperson can be with facts.

Email Harvey Freedenberg at, or follow him on Twitter @HarvF.