Like many a good mystery, Elizabeth Kolbert’s book The Sixth Extinction: An Unnatural History depicts this crime through the unblinking eyes of an impartial observer. Characters and readers may have emotional reactions to the plot, but not our objective narrator. She is matter-of-fact.
Kolbert establishes the facts of her case at the outset: We are losing species at a rate thousands of times greater than at any previous point in human history. Those species are dying off for a variety of reasons, but nearly all the causes — spreading diseases, shifting ocean chemistry, habitat destruction — stem from human expansion and our rapid industrialization of the planet throughout the past 300 years.
The deaths are accelerating, along with humanity’s impact on habitats worldwide. So, we have a crime. We know the perpetrator. But we don’t yet have a confession.
Kolbert traces a thread of stubborn human denial. In the 18th century, most people couldn’t fathom that any creature that had once lived on Earth could have conclusively disappeared. Extinction was a difficult concept to grasp, partly because the idea implied that God’s creation may not have been as perfect as humans had originally believed. Worse yet, some species seemed to have been annihilated because of human hunting, meaning human beings may have permanently altered God’s creation. As researchers unearthed fossils and other evidence of long-extinct species, however, public opinion gradually came to accept the idea that species don’t necessarily last forever, and that humans can play a major role in their extinction.
In the 19th century, we had a hard time swallowing the revolutionary concept of evolution. Darwin asked us to believe that not only were the original creatures that populated the planet largely gone, but also that change is ever-present, and that creatures alive today — including human beings — continue to evolve under the influence of natural selection.
The recent theory that humans are to blame for the Sixth Extinction may be the most difficult of all for us to accept. The five previous major extinctions stemmed from a variety of origins, from volcanic explosions to the impact of huge asteroids. Today, however, the scientists who accompanied Kolbert to islands, mountaintops and rain forests around the world are recording a relatively slow global catastrophe, and the causes and effects can be hard to track. We know we’re altering our climate, and that acids from fossil fuels are changing ocean chemistry and wiping out thousands of species, but identifying and tracking chemical changes in mediums as big as the oceans takes painstaking research.
Some aspects of this extinction are easy to see. Many of the world’s largest and most visible species — bears, tigers, rhinoceroses — are simply being squeezed out of their habitats by encroaching human development. We have cut down forests, plowed up grasslands, and built cities across environments where big mammals used to live.
Two mysteries remain unsolved at the end of Kolbert’s tale: Will humans acknowledge the evidence and our responsibility to reverse the progress of the Sixth Extinction? And, if we don’t, will the habitats’ deterioration eventually halt the mass extinction by eliminating its root cause — us?