The Best American Science and Nature Writing 2014 (28 page)

Fertilizer plants produce more nitrogen than is fixed naturally by all terrestrial ecosystems.

Humans use more than half of the world's readily accessible freshwater runoff.

 

Most significant, Crutzen noted, 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 more than a third in the past two centuries, while the concentration of methane, an even more potent greenhouse gas, has more than doubled. Just a few more decades of emissions may bring atmospheric CO
₂
to a level not seen since the mid-Miocene, 15 million years ago. A few decades after that, it could easily reach a level not seen since the Eocene, some 50 million years ago. During the Eocene, palm trees flourished in the Antarctic and alligators paddled around the British Isles.

“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 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.

Zalasiewicz noticed that most of those using the term were not trained in the fine points of stratigraphy, and he wondered how his colleagues felt about this. At the time, he was head of the Geol Soc's stratigraphy committee, and during a meeting one day he asked the members what they thought of the Anthropocene. Of the twenty-two stratigraphers present, twenty-one thought that the concept had merit.

“My response was it's a very interesting and powerful idea,” Andy Gale, a professor at the University of Portsmouth, told me. “I felt it was worthwhile to pursue, because it's an important tool for making people think.”

The group decided to approach the concept as a formal problem. Would the Anthropocene satisfy the stratigraphic 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.) After a year's worth of study, the answer that the group arrived at was an unqualified yes. Among other things, the members observed in a paper summarizing their findings, the Anthropocene will be marked by a unique “biostratigraphic 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, giant rats.

 

Just as in the early years of the Geol Soc, stratigraphers today spend a lot of time arguing about borders. A few years ago, after much heated discussion, members of the ICS voted to move the start of the Pleistocene epoch from about 1.8 million to about 2.6 million years ago. This decision was part of a broader, and even fiercer, debate about whether to do away with the Quaternary, the period that spans both the Pleistocene and the Holocene, and fold it into the Neogene. (The elimination of the Quaternary was vigorously—and ultimately successfully—resisted by Quaternary stratigraphers.)

The debate over the Anthropocene's borders is complicated by the fact that the geology of the epoch is, at this point, almost entirely prospective. The way stratigraphers usually define boundaries—once they've stopped arguing about them—is by choosing a particularly fossil-rich sequence of rocks to serve as a reference. These reference sequences are colloquially known as “golden spikes”—technically, they're called Global Boundary Stratotype Sections and Points, or GSSPs—and they're scattered around the world (though a disproportionate number are in Europe). The striped rocks at Dob's Linn have been designated the golden spike for the start of the Silurian period. For the base of the Carboniferous, the golden spike is near the town of Cabrières, in southern France, and for the start of the Triassic it's in the hills of Meishan, China. (The Chinese have tried to turn this last golden spike into a tourist destination, with a manicured park and a statue of a tooth from a once common eel-like creature known as a conodont.)

Since the rocks of the Anthropocene don't yet exist, it's impossible to choose an exemplary sequence of them. To stratigraphers, then, a key, but also rather vexing, question is what could serve instead of the traditional golden spike. In 2009 the ICS set up an Anthropocene Working Group to examine this and related issues; not surprisingly, Zalasiewicz was appointed chairman. At the time of our visit to London, he told me that he thought there were many possible ways that the start of the epoch could be designated. One would simply be to choose a date—1800, say, or 1950. This is how geological periods of the deep, pre-fossiliferous past are defined; what's known as the Neoproterozoic era, for example, is said to have begun precisely one billion years ago.

Another possibility would be to use nuclear fallout. The aboveground tests of the mid-twentieth century dispersed radioactive particles all around the globe. Some have half-lives of more than a thousand years; in a few cases, like uranium-236, the figure is in the tens of millions. To future geologists, the fallout will thus present a novel radioactive “spike” (assuming, that is, that the future does not hold a nuclear war). This sort of geochemical marker is used to define the end of the Cretaceous. The impact that occurred during the final seconds of the period left behind a thin layer of sediment containing anomalously high concentrations of the element iridium—the so-called iridium spike.

Yet another possibility is to use the world's subway systems, an idea that also has precedent in deep time. Geologists refer to the outlines of burrows that creatures left behind in the sediments as “trace fossils.” The start of the Cambrian period, some 540 million years ago, is defined as the point when the first complex burrows appear; these left impressions in the rocks that resemble scattered grains of rice. (No one is sure what the animals that made the burrows looked like, as their bodies have not been preserved.) London's subway system, the world's oldest, will leave behind an enormous set of trace fossils, as will New York's and Seoul's and Paris's and Dubai's.

“All the great world cities have underground systems now,” Mark Williams, a stratigrapher who teaches at the University of Leicester and is a member of the Anthropocene Working Group, noted. “They're extensive, they're fairly permanent from a geological perspective, and they're a very, very good indicator of the complexity that's come to characterize the twentieth and twenty-first centuries.”

Williams told me that the response to the idea of formalizing the Anthropocene had “generally been very positive.” (Just in the past few months, three new academic journals focusing on the Anthropocene have been launched.) But, as is to be expected from a group that can sustain a decade-long disagreement about the status of the Quaternary, there's still plenty of dissent. Some critics argue that humans have been altering the planet for thousands of years already, so why get all worked up about it now!'

“We can see that human interactions with the landscape are increasing,” Philip Gibbard, a stratigrapher at Cambridge, told me. “No one disputes that. We build buildings. We build towns. We build roads. We drop plastic bags in the ocean. All that's absolutely true. But from a geological perspective—and I have to speak as a geologist, not as a generally interested person—I think what's happening now is just a logical continuation of something that began as human populations started to increase at the beginning of the Holocene.

“It is quite exciting to pursue this new idea,” he added. “But I'm suspicious of it.”

Other critics are skeptical of the idea for opposite reasons. They point out that human impacts on the planet are likely to become even more pronounced, and hence more stratigraphically significant, as time goes on. Thus, what's sometimes referred to in geological circles as the “event horizon” has not yet been reached.

For his part, Zalasiewicz is sympathetic to both lines of argument. Humans
have
been altering the planet for quite a while, though probably the impacts of the past were orders of magnitude more modest than they are today. And a few centuries from now the impacts of human activity may be orders of magnitude greater again. By the time people are through, Zalasiewicz told me, he wouldn't be surprised if the earth were rendered more or less unrecognizable. “One cannot exclude a P-T-type outcome,” he observed, referring to the worst of the so-called Big Five, the end-Permian, or Permo-Triassic, extinction. In the meantime, though, he said, “we have to work with what we've got.”

 

This past summer, I went with Zalasiewicz on another collecting trip, this one to Wales. Zalasiewicz has a special fondness for the country. He wrote his dissertation on the stratigraphy of northern Wales, and while finishing his research he drove around in a decommissioned postal van and lived in a camper that had been used as a chicken coop. He wanted to show me a spot near the town of Ponterwyd where he thought there should perhaps be another golden spike—in this case, marking the base of the Aeronian Stage of the Silurian. We set out from the town of Keyworth, in Nottinghamshire, where Zalasiewicz lives with his wife and teenage son, and drove through the West Midlands. In its day the West Midlands was the industrial heart of Britain. Now the industry is mostly gone, and people struggle to find work. “About as scary an advertisement for the Anthropocene as you can imagine” is how Zalasiewicz described the region.

When we arrived at Ponterwyd, smirr was falling or, as the Welsh put it, piglaw. Again there were lots of sheep and green, sheep-shorn hills and rocks filled with fossils. Banging away at an outcropping, I soon found several graptolites. One, which Zalasiewicz identified as belonging to the species
Monograptus triangulatus
, looked like a tiny saw blade, with miniature triangular teeth. With characteristic tact, he told me that my specimen was “very lovely.” I stuck it in my bag.

A few days later, I took the train back to London and then the Tube out to Heathrow, where I was spending the night at an airport hotel. Thanks to all the graptolites I'd gathered, my suitcase was overweight, and I decided that I was going to have to deaccession some of them. I took what seemed to be the least impressive examples and headed out through the lobby, only to realize that there was nowhere to go. The hotel faced a ten-foot wall, which was made of plywood and covered with billboard-size sheets of plastic printed with photographs of trees. The photos kept repeating, so that walking along was like getting lost in a dark monoculture. Beyond the plywood wall, there was a parking lot, and beyond that an access road. I figured that the parking lot would have to do. By this point I'd spent enough time with Zalasiewicz that the place appeared to me as a mosaic of human impacts. The lot was edged with a margin of dirt; this was filled with scraggly plants, many of them no doubt introduced species. Strewn among the weeds was the usual flotsam of travel: empty water bottles, crumpled candy wrappers, crushed soda cans, half-eaten packages of crisps. I recalled what Zalasiewicz had told me about aluminum, which is that until the late nineteenth century it did not exist on earth except in combination with other elements. So soda cans may provide yet another marker of our presence: the Dr Pepper spike.

It was a lovely evening. A half-moon hung in a purple sky crisscrossed by jet contrails. I took out my graptolites. Most I couldn't identify, but one, I thought, belonged to the species
Rhaphidograptus toernquisti
, which Zalasiewicz had described to me as among life's great success stories.
Rhaphidograptus toernquisti
managed to persist, unchanged, for some five million years. I placed my fossils in a little pile next to a discarded cigarette pack. Nearby I noticed a plastic pouch with the word
TOXIC
printed in block letters. The pouch was torn, and some ominously bright yellow powder was leaking out of it. I tried to imagine a geologist in the year
A.D.
100,000,000 stumbling onto the site. It was hard for me to picture what he (or it) would look like, but I got a certain satisfaction thinking about how puzzled he would be when he came upon my Silurian graptolites nestled amid the wreckage of the Anthropocene.

FROM
The Atlantic

 

L
INDA CAMPBELL WAS
not quite four years old when her appendix burst, spilling its bacteria-rich contents throughout her abdomen. She was in severe pain, had a high fever, and wouldn't stop crying. Her parents, in a state of panic, brought her to the emergency room in Atlanta, where they lived. Knowing that Campbell's organs were beginning to fail and her heart was on the brink of shutting down, doctors rushed her into surgery.

Today removing an appendix leaves only a few droplet-size scars. But back then, in the 1960s, the procedure was much more involved. As Campbell recalls, an anesthesiologist told her to count backward from ten while he flooded her lungs with anesthetic ether gas, allowing a surgeon to slice into her torso, cut out her earthworm-size appendix, and drain her abdomen of infectious slop, leaving behind a lengthy longitudinal scar.

The operation was successful, but not long after Campbell returned home, her mother sensed that something was wrong. The calm, precocious girl who had gone into surgery was not the same one who emerged. Campbell began flinging food from her high chair. She suffered random episodes of uncontrollable vomiting. She threw violent temper tantrums during the day and had disturbing dreams at night. “They were about people being cut open, lots of blood, lots of violence,” Campbell remembers. She refused to be alone but avoided anyone outside her immediate circle. Her parents took her to physicians and therapists. None could determine the cause of her distress. When she was in eighth grade, her parents pulled her from school for rehabilitation.