Over the years, a number of different names have been suggested for the new age that humans have ushered in. The noted conservation biologist Michael Soulé has suggested that instead of the Cenozoic, we now live in the “Catastrophozoic” era. Michael Samways, an entomologist at South Africa’s Stellenbosch University, has floated the term “Homogenocene.” Daniel Pauly, a Canadian marine biologist, has proposed the “Myxocene,” from the Greek word for “slime,” and Andrew Revkin, an American journalist, has offered the “Anthrocene.” (Most of these terms owe their origins, indirectly at least, to Lyell, who, back in the eighteen-thirties, coined the words Eocene, Miocene, and Pliocene.)
The word “Anthropocene” is the invention of Paul Crutzen, a Dutch chemist who shared a Nobel Prize for discovering the effects of ozone-depleting compounds. The importance of this discovery is difficult to overstate; had it not been made—and had the chemicals continued to be widely used—the ozone “hole” that opens up every spring over Antarctica would have expanded until eventually it encircled the entire earth. (One of Crutzen’s fellow Nobelists reportedly came home from his lab one night and told his wife, “The work is going well, but it looks like it might be the end of the world.”)
Crutzen told me that the word “Anthropocene” came to him while he was sitting at a meeting. The meeting’s chairman kept referring to the Holocene, the “wholly recent” epoch, which began at the conclusion of the last ice age, 11,700 years ago, and which continues—at least officially—to this day.
‘Let’s stop it,’ Crutzen recalled blurting out. ‘We are no longer in the Holocene; we are in the Anthropocene.’ Well, it was quiet in the room for a while.” At the next coffee break, the Anthropocene was the main topic of conversation. Someone came up to Crutzen and suggested that he patent the term.
Crutzen wrote up his idea in a short essay, “Geology of Mankind,” that ran in Nature. “It seems appropriate to assign the term ‘Anthropocene’ to the present, in many ways human-dominated, geological epoch,” he observed. Among the many geologic-scale changes people have effected, Crutzen cited the following:
• Human activity has transformed between a third and a half of the land surface of the planet.
• Most of the world’s major rivers have been dammed or diverted.
• Fertilizer plants produce more nitrogen than is fixed naturally by all terrestrial ecosystems.
• Fisheries remove more than a third of the primary production of the oceans’ coastal waters.
• Humans use more than half of the world’s readily accessible fresh water run- off.
Most Significantly, Crutzen said, people have altered the composition of the atmosphere. Owing to a combination of fossil fuel combustion and deforestation, the concentration of carbon dioxide in the air has risen by forty percent over the last two centuries, while the concentration of methane, an even more potent greenhouse gas, has more than doubled.
“Because of these anthropogenic emissions,” Crutzen wrote, the global climate is likely to “depart significantly from natural behavior for many millennia to come.”
Crutzen published “Geology of Mankind” in 2002. Soon, the “Anthropocene” began migrating out into other scientific journals.
“Global Analysis of River Systems: From Earth System Controls to Anthropocene Syndromes” was the title of a 2003 article in the journal Philosophical Transactions of the Royal Society B.
“Soils and Sediments in the Anthropocene” ran the headline of a piece from 2004 in the Journal of Soils and Sediments.
When Zalasiecicz came across the term, he was intrigued. He noticed that most of those using it were not trained stratigraphers, and he wondered how his colleagues felt about this. At the time, he was head of the stratigraphy committee of the Geological Society of London, the body Lyell and also William Whewell and John Phillips once presided over. At a luncheon meeting, Zalasiewicz asked his fellow committee members what they thought of the Anthropocene. Twenty-one out of the twenty-two thought that the concept had merit.
The group decided to examine the idea as a formal problem in geology. Would the Anthropocene satisfy the criteria used for naming a new epoch? (To geologists, an epoch is a subdivision of a period, which, in turn, is a division of an era: the Holocene, for instance, is an epoch of the Quaternary, which is a period in the Cenozoic.) The answer the members arrived at after a year’s worth of study was an unqualified “yes.” The sorts of changes that Crutzen had enumerated would, they decided, leave behind “a global stratigraphic signature” that would still be legible millions of years from now, the same way that, say, the Ordovician glaciation left behind a “stratigraphic signature” that is still legible today. Among other things, the members of the group observed in a paper summarizing their findings, the Anthropocene will be marked by a unique “biostratigraphical signal,” a product of the current extinction event on the one hand and of the human propensity for redistributing life on the other. This signal will be permanently inscribed, they wrote, “as future evolution will take place from surviving (and frequently anthropogenically relocated) stocks.” Or, as Zalasiewicz would have it, rats.
By the time of my visit to Scotland, Zalasiewicz had taken the case for the Anthropocene to the next level. The lnternational Commission on Stratigraphy, or ICS, is the group responsible for maintaining the official timetable of earth’s history. It’s the ICS that settles such matters as: when exactly did the Pleistocene begin? (After much heated debate, the commission recently moved that epoch’s start date back from 1.8 to 2.6 million years ago.) Zalasiewicz had convinced the ICS to look into formally recognizing the Anthropocene, an effort that, logically enough, he himself was put in charge of. As head of the Anthropocene Working Group, Zalasiewicz is hoping to bring a proposal to a vote by the full body in 2016. If he’s successful and the Anthropocene is adopted as a new epoch, every geology textbook in the world immediately will become obsolete.
Elizabeth Kolbert is a staff writer at The New Yorker. She is the author of Field Notes from a Catastrophe: Man, Nature, and Climate Change.
From The Sixth Extinction: An Unnatural History Copyright © 2014 by Elizabeth Kolbert. Reprinted with the permission of Henry Holt and Company, LLC.