Since early Roman times, prophets, popes, and preachers have been predicting the end of the world. Undeterred by their folly, some, like the Puritan minister Cotton Mather, simply postdated their predictions each time the world proved them wrong. So what are we to make of scientists who argue that the end is nigh, who believe that mankind’s sins against nature have put us on a path to a kind of hell on Earth? How does a secular society steeped in skepticism about such matters come to grips with an apocalyptic scenario as potentially horrific as anything imagined by Billy Sunday or Pat Robertson?
In her Pulitzer Prize-winning book The Sixth Extinction: An Unnatural History (2014), environmental journalist Elizabeth Kolbert assumes the role of a secular prophet, albeit a cautious one, as she warns of what can happen if we continue to interfere with the Earth’s biological systems. “By disrupting these systems — cutting down tropical rainforests, altering the composition of the atmosphere, acidifying the oceans,” she writes, “we’re putting our own survival in danger.” Kolbert gives a lecture on “The Fate of the Earth” at the Lensic Performing Arts Center on Friday, June 1, in a presentation of the School for Advanced Research and The Nature Conservancy in New Mexico.
Kolbert carefully grounds her warning about the future in historical precedents. There’s nothing far-fetched about the prospect of a mass extinction once it has been made clear that such extinctions not only occurred in the past but resulted from the same kinds of damage to life-sustaining systems that we are inflicting today. Kolbert’s story begins with the big chill that ended the Ordovician Period, roughly 450 million years ago. Plummeting temperatures, followed by worldwide glaciation, wiped out 85 percent of marine organisms at a time when most living things were aquatic. It was the first of at least two mass extinctions caused by extreme climate change.
The early 19th-century French naturalist Georges Cuvier was the first scientist to theorize that the Earth had been wracked by mass extinctions, but it took nearly 200 years for his peers to accept the idea. Charles Darwin was acidly dismissive, writing, “So profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do not see the cause, we invoke cataclysms to desolate the world!”
Darwin believed that extinctions occur gradually as new species replace old ones. His theory held sway until the early 1990s, when Nobel physicist Luis Alvarez and his son Walter, a geologist, found convincing evidence that a giant asteroid, packing the power of a million H-bombs, collided with Earth 65 million years ago. “Debris, including iridium from the pulverized asteroid, spread around the globe,” Kolbert writes. “Day turned to night and temperatures plunged.” A mass extinction ensued, taking with it the dinosaurs, along with three-quarters of all living things. A decade of detective work by the Alvarezes led to the incontestable conclusion that life on Earth could be wiped out, as British paleontologists Anthony Hallam and Paul Wignall write, “in a geologically insignificant amount of time.” Darwin’s repudiation of mass extinctions was proved wrong; settled science was upended. The issue was no longer whether the world was vulnerable to catastrophic forces but whether we could see the trouble coming in time to stop it.
In The Sixth Extinction, Kolbert deftly guides us through 500 million years of geologic history, chronicling five mass extinctions caused by rampaging natural forces before arriving at her pivotal contention that the planet is on the threshold of a sixth extinction, for which we are responsible. At this point, the book takes a speculative turn as she gives voice to some of the scarier prognosticators in the field of climate science. She quotes Lee R. Kump of Penn State, who writes with colleagues Timothy J. Bralower and Andy Ridgway in the journal Oceanography that we are likely to leave a legacy that ranks “as one of the most notable, if not cataclysmic events in the history of our planet.”
Not that Kolbert overstates the capacity of humans to wreak havoc on nature. Her chronicling of man’s handiwork, from the slaughter of the great auk to the deforestation of the Amazon basin, ought to be part of every school curriculum. But whether or not the damage we have inflicted with habitat destruction and climate change is comparable to the upheavals of past extinctions is debatable. It’s quite possible, Kolbert contends, that rising levels of carbon dioxide in the atmosphere — the main driver of climate change — could trigger an extinction event that starts to look apocalyptic. The hypothesis is dependent on the assumption that climate change is settled science, and that global average temperatures will soar high enough to have calamitous impacts on biodiversity, sea-level rise, and human health.
A number of experts dispute the idea that we are anywhere near a sixth extinction. “Many of those making facile comparisons between the current situation and past mass extinctions don’t have a clue about the difference in the nature of the data, much less how truly awful the mass extinctions recorded in the marine fossil record actually were,” Smithsonian paleontologist Doug Erwin told The Atlantic in a 2017 interview. Peter Brannen, science journalist and author of The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth’s Past Mass Extinctions (Ecco/HarperCollins, 2017), agrees in his book. No matter how alarming, the extinction rate over the past several centuries does not begin to rival the previous five mass extinctions. Yet neither Erwin nor Brannen rule out the possibility of a sixth extinction. “I think that if we keep things up long enough, we’ll get to a mass extinction,” Erwin said. How long is “long enough”? According to Brannen, wildlife today accounts for only 3 percent of the planet’s land animals. Human beings, livestock, and pets take up the remaining 97 percent. Industrial trawlers have removed about 90 percent of all large ocean predators, including halibut, tuna, grouper, swordfish, marlin, and sharks. Even butterflies have declined by 35 percent over the past 50 years.
So, what is the difference between a true mass extinction and the mounting death toll that Brannen documents? Are we dealing in academic distinctions? Not if we consider that human life could be at stake in a mass extinction. A recent report by scientists from the Scripps Institution of Oceanography warn that there is an outside chance that CO2-driven global warming could rise by more than 5 degrees Celsius above preindustrial levels by 2100, high enough to put nearly one-quarter of the world’s projected population at risk. The report is at the extreme end of climate prognostication.
A more recent paper published in Nature earlier this year estimates the high end of likely warming at 4.5 degrees, with a fewer than 1 percent chance of temperatures rising higher than that. If climate scientists agree on anything these days, it’s that keeping the global average temperature increase to a manageable 2 degrees is looking less and less likely. With a greater than 2-degree increase, the risks of severe damage to Earth’s biodiversity and the world economy is high to very high, according to the UN’s Intergovernmental Panel on Climate Change.
The amount of CO2 in the atmosphere, 410 parts per million, is already almost 50 percent higher than it was in the 1880s at the dawn of the Industrial Revolution. The planet has not experienced those levels since the Pliocene Epoch, three million years ago, when sea levels were about 66 feet higher. Kolbert thinks CO2 levels may well reach 500 parts per million by mid-century, which would cause global temperatures to rise as high as 4 degrees Celsius. This, in turn, would trigger a variety of world-altering events, she writes, including the disappearance of most remaining glaciers, the inundation of low-lying islands and coastal cities, the melting of the Arctic ice cap, and the extirpation of the world’s coral reefs.
Survival depends on adaptability. Extinction happens when living things suddenly find themselves facing conditions for which evolution has not prepared them. The world will warm up enough in coming years, Kolbert writes, that our ability to adapt will surely be tested. “It’s quite possible that by the end of this century, CO2 levels will reach a level not seen since the Antarctic palms of the Eocene, some fifty million years ago. Whether species still possess the features that allowed their ancestors to thrive in that ancient, warmer world is, at this point, impossible to say.” ◀
