by Curt Stager
DEEP
FUTURE
THE NEXT 100,000 YEARS
OF LIFE ON EARTH
CURT STAGER
For Kary
Contents
Cover
Title Page
Prologue
1 Stopping the Ice
2 Beyond Global Warming
3 The Last Great Thaw
4 Life in a Super-Greenhouse
5 Future Fossils
6 Oceans of Acid
7 The Rising Tide
8 An Ice-Free Arctic
9 The Greening of Greenland
10 What About the Tropics?
11 Bringing It Home
Epilogue
References
Index
Acknowledgments
About the Author
ALSO BY CURT STAGER
Copyright
About the Publisher
Prologue
Out of the earth has come a creature that has
changed … the face of continents, that has
harnessed the forces of the earth and turned
them against themselves.
—John Burroughs, Accepting the Universe
Welcome to the Age of Humans, a new chapter of Earth’s history whose name has already entered the lexicon of mainstream science.
Welcome to the end of the natural world as a realm that is somehow meaningfully distinct from humanity, thanks in large part to the worldwide carbon pollution that you and I have unwittingly helped to create and that will affect our descendants for many thousands of years, far longer than most of us yet realize.
And welcome to this peek beyond the curtain of 2100 AD, which currently marks the outer temporal limits of most thought and debate about modern climate change. As you’ll soon see, the environmental consequences of our actions today are so large, powerful, and long-lived that they cannot be fully understood from a mere century-scale point of view.
My aim in these pages is to introduce you to a broader perspective on global warming than the one most readers are familiar with, the one that considers “long-term” climate change to be a trend that merely stretches over several years or decades. People like Bill McKibben and Al Gore have brought the planetary scope of CO2 pollution to the attention of millions, but for most of us, the element of time has yet to be fully explored. David Archer, a farsighted climate modeler whose work I will introduce later in the book, has described the situation thus: “The idea that anthropogenic CO2 release may affect the climate … for hundreds of thousands of years has not yet reached general public awareness.” The time has come to move on from unproductive, politicized arguments over global warming to the next stage of inquiry, where it is no longer a question of if it is happening but of when, how much, and for how long.
At first, it might seem strange that an environmental historian, or paleoecologist, like myself should be writing about future events like this. I read the stories of ecosystems that lie stacked in archives not of paper but of mud. My specialty is collecting layered core samples from the bottoms of lakes and bogs in the Adirondacks, Peru, and much of Africa, picking out the remains of microscopic organisms that once lived and died there and reconstructing past climates from the patterns of change they reveal. A layer of salt-loving algae tells me that the local climate was once dry enough to lower the lake level and turn the water brackish. A slug of pollen in another layer attests to wetter conditions that favored forests over deserts.
What a paleoecologist contributes most naturally to this prediction business is a sense of time. Much of what lies ahead of us has already happened before, and those of us with a long-term view of environmental history can often recognize familiar age-old processes in action today as well as likely consequences that may come as a result. We who combine the biological and geological sciences in our historical research also become used to thinking in broad terms that include both the living and nonliving worlds. But more to the point, we also think “deep.” For us, a century or millennium may be just an appetizer on the menu, and the duration of a single human lifetime is, statistically speaking, insignificant.
That’s not always a popular position, of course. A long view is not necessarily welcome to those who are preoccupied with events in the here and now, but it nonetheless offers potentially useful compass bearings for navigation in a complex and changing world. As a guide on this tour of the future, I’ll look beyond the present moment to focus both forward and backward in time, bringing into view the nature of things to come as well as things that have long since been.
The relatively few scientists who have looked deeply into our future like this see the lingering climatic and ecological effects of fossil fuel carbon stretching well beyond the end of the twenty-first century. In order to follow their lines of sight through these pages, we will need to train the mind’s eye to take in tremendous sweeps of Earth history, both past and future. Much of what we learn here will come from geoscientists who speak of eras and epochs as the rest of us speak of seasons, people who share with the superrich a close working familiarity with the significance of terms like “million” and “billion.” To these professional time specialists, the Eocene and Pleistocene epochs are as real as World War II or the turbulent 1960s are to the rest of society, and they see in those long-gone ages some important lessons that can guide us as we struggle to understand what is happening around us today.
Before we go further in this quest, though, I would like to introduce you to a newly minted technical term that’s currently striking resonant chords in the scientific community. At the moment, it still sounds foreign to most ears, but for those who are familiar with it the word represents an almost thrilling acknowledgment of our place in the grand arc of geologic time. It’s modeled in the form of other major subdivisions of the fossil record that include what some call the Age of Fishes or the Age of Dinosaurs. Now that human influence has touched almost every cranny of the Earth, a new age has dawned, and it needs a formal name.
In the arcane lexicon of geological nomenclature, this age best qualifies as the latest in a string of episodes known as “epochs” that began 65 million years ago with the demise of the dinosaurs. You might have heard of them before, if you’ve spent much time learning about fossils. The post-dinosaur years began with the warm Paleocene, whose prefix paleo (Greek for “ancient”) refers to its great age relative to others that came later. Next came the even warmer Eocene, which saw the early-morning stages of modern mammal evolution. After skipping through three more epochs (Oligocene, Miocene, and Pliocene), each with a distinctive story of evolving life to tell, we find the Earth cooling down during the Pleistocene, and come, at last, to the climatically mild Holocene (“recent whole”), which began 11,700 years ago and traditionally includes the ever-advancing present.
But keep on the alert for a new epochal name that was recently bestowed upon this Age of Humans. No, it’s not the “Plasticene,” though blogger Matt Dowling has indeed proposed that label with tongue planted firmly in cheek. Partial credit for promoting the new name goes to atmospheric chemist and Nobel laureate Paul Crutzen, but it actually originated with aquatic ecologist Eugene Stoermer. Now an emeritus scholar at the University of Michigan, Stoermer recently told me that his catchy term spread informally through the scientific grapevine before appearing in print several years ago under the joint authorship of Crutzen and himself.
“I can’t remember exactly how it first came to mind,” he recalled, chuckling like a pleased but somewhat surprised parent whose kid has grown up to become a celebrity. “I used it in conferences here and there, and it eventually caught people’s attention.” That’s not surprising, though, because Stoermer’s term neatly defines these and near-future times as indelibly marked by anthropogen
ic, or human-generated impacts, and it’s seeping more and more comfortably into the writings and speech of scientists and lay folk around the world.
So here’s your chance to impress your friends, if you’re the type who likes to show off by using the latest technical jargon that describes not only recent human history but also the next hundreds of thousands of years of it that are yet to come. Tell them, in the course of casual conversation, “Welcome to the Anthropocene.” (Stoermer pronounces it ANthropocene, but anTHROPocene also works.)
By most definitions, the Anthropocene began during the 1700s when our greenhouse gas emissions started to change the atmosphere significantly. But our influences actually extend far beyond climate alone. The formerly dark portion of Earth that faces away from the sun now glows with electric light, as if it were illuminated by billions of fireflies. According to Crutzen, our fishing industries remove more than a third of the primary productivity of temperate coastal areas every year. Farmers sprinkle, spray, and spade more nitrogen fertilizer than is naturally deposited on all the world’s forest floors, savanna turf, and bird rookeries combined. And species extinctions today are beginning to outpace any in the history of life.
A small but active corps of visionary scientists is now sketching the broad outlines of what the Anthropocene holds in store for us. But before looking further into the surprising details of what is to come, it’s worth noting that we are not the only living things to have changed the atmosphere so much. From a biologist’s emotionally detached perspective, there is nothing particularly unusual about the human tendency to pollute our environment; every organism produces waste, and the more organisms that exist in a given habitat the more unwanted by-products they produce. It’s just that we humans have now become so numerous, so widespread, and so adept at consuming natural resources that our wastes are polluting the entire planet, even to the point of changing its climate. In that sense, we’re becoming victims of our own success as a species.
The first such global pollution crisis was actually the work of marine bacteria, and it struck just over 2 billion years ago at a time when all life on Earth was single-celled. The pressures of mutation and natural selection drove some pioneering microbes to overuse a new way of harnessing the energy of sunlight—what we now call photosynthesis. Unfortunately for most of the other diminutive life-forms of the time, that primordial biotechnology also released a dangerous waste gas into the surroundings. That waste gas was free oxygen.
Excess oxygen steadily polluted the oceans as they grew greener and greener with the tint of chlorophyll and the atmosphere grew more and more corrosive as a result. Formerly gray or black rocks crumbled into reddened remnants of their former selves as the iron particles within them rusted. Any species that could not repair the ravages of oxidation in their cells perished or lived imprisoned in protective aquatic muds. Descendants of those microbial refugees still cower in the fetid muck of marshes and in the oxygen starved depths of certain lakes and seas. We unwittingly harbor legions of benign oxygen haters in the dark recesses of our digestive tracts, and some legumes such as soybeans pack their root nodules with blood-colored, oxygen-binding compounds that shield their resident bacteria, thereby earning paybacks in the form of microbial nitrogen fertilizer.
If language had existed back then in that purely microbial world, headlines would have heralded the advent of a global oxygen catastrophe. Perhaps bacterial alarmists who warned of that first pollution disaster would have described us humans as monstrous, two-legged versions of the “cockroaches that will take over the world after it’s been poisoned.” In fact, both our distant ancestors and those of modern cockroaches did indeed populate the world only after photosynthetic oxygen made it habitable for animal life.
High above the early oceans, the novel molecules spawned new by-products just as the chemical stew of modern smog does today. Oxygen in the upper reaches of the atmosphere clumped into heavy, tripled clusters and accumulated as a layer of invisible ozone that blocked much of the sun’s dangerous ultraviolet radiation. Meanwhile, down below, some of the primitive single-celled survivors of the oxygen pollution crisis were developing ways to use the poisonous gas as a source of energy in its own right. Eventually, Earth’s first wriggly protozoans learned to harness oxygen’s destructive power to convert the bodies of their smaller neighbors into useful food, and the rest is predatory history.
Today, the waste gas of photosynthesis contaminates a fifth of the air in our lungs and we, the descendants of those first polluters, can’t live without it. When the world changes so dramatically, there must always be winners and losers. In this case, we have clearly been among the winners.
About a billion and a half years after the oxygen crisis, early plants that inherited the solar technology of photosynthesis were turning it to new uses of their own. Where the power of sunlight once supported only singular, free-living cells, increasingly large and abundant land plants used it to coax CO2 molecules from the air, dissect them, and bind their carbon atom components into the fabrics of branches, trunks, leaves, seeds, and spores.
Growing atom by atom, like living crystals, primeval swamp forests hoarded precious carbon. Photosynthetic life plucked CO2 from a thin gaseous soup in which the target element, carbon, was outnumbered more than ninety-nine to one by oxygen and nitrogen. At death, they took the concentrated carbon troves to their watery graves and were buried, layer upon layer, in mausoleum vaults of mud.
Hundreds of millions of years later, the first hints of Stoermer and Crutzen’s Anthropocene began with another biogenic pollution event. Our industrial ancestors unearthed some of those black fossil deposits, called them coal, and set fire to them. Heated in the presence of oxygen, the purified carbons disintegrated back into diffuse swarms of CO2 molecules, unleashing the hot solar energy of countless Paleozoic summers as their ancient chemical bonds snapped and cast them skyward.
Though at first indistinguishable from the other CO2 molecules circulating among plants, animals, waters, and winds today, these fossil fumes are different. Most of the CO2 that enters the air from breath, forest fires, oceanic upwellings, and rot is quickly recycled; about as much carbon is absorbed by photosynthetic bacteria, algae, and plants each year as is released by respiration, and roughly as much of it dissolves into the ocean surface as is naturally degassed from it. At the global level, only a small fraction is lost to sediment burial over the course of a year and only relatively modest amounts hiss from volcanic vents, so the total amount in circulation normally varies little.
Fossil fuel carbons, in contrast, are outsiders. Though some manage to rejoin the ebb and flow of modern life, most join the ranks of the footloose unemployed, swelling the pool of airborne CO2 faster than other processes can reduce it. Just before the dawning of the Anthropocene, a random sample of a million air molecules would have netted you about 280 carbon dioxides. As I write this I could land 387 or so, many of which emerged from smokestacks and tailpipes within the last 250 years.
Why does this modern pollution spree deserve a new, formal geological name? Even though it represents less than I percent of the gases in the atmosphere, the growing surplus of CO2 is now making the world hotter than it would otherwise be. Likewise, geologists designated the last two epochs largely on the basis of their climatic conditions; the Pleistocene was dominated by numerous glacial coolings and the Holocene was the latest of several shorter interglacial warm spells, the one during which the first complex human civilizations were born.
As I’ll explain later, the greenhouse gas pollution of the Anthropocene will hang around long enough to cancel the next ice age, and the result is that this human-driven epoch may last an order of magnitude longer than the Holocene did. Incredibly, it is we—specifically those of us who live in the twenty-first century—who will do the most to determine its duration. The epochal name is well chosen; this Age of Humans is the product, the environmental backdrop, and the geological trademark of our species.
To some, the Anthr
opocene marks the end of nature as an entity separate from the apelike Homo sapiens species that it spawned in Africa long ago. Much of this conception of humans as privileged occupiers of some lofty plane above other species dates back to Aristotle’s Scala Naturae, which is often translated as “The Great Chain of Being.” It pictures a ladder or interlocking chain of existence that positions more complex animals above simpler ones and a heavenly creator above all. Because humans in this view combine both physical and metaphysical traits, they form a unique link that joins the celestial and earthly realms. Vestigial traces of the concept still linger in biological nomenclature that classifies complex-looking orchids as “higher plants” and simple-looking mosses as “lower plants.” In society at large, it crops up in such terms as “the missing link,” the theoretical hairy ape-human that would forge a lowly, anchoring ring in the great chain between us and other primates.
To most biologists today, however, the idea that humans are meaningfully separate from nature is rather old school. Our very ability to change climate on a global scale, simply by emitting our daily wastes, attests to our intimate connection with our physical surroundings. One could even argue that this kind of self-centered and shortsighted conceit, the idea that we are somehow exempt from the ancient laws of the physical world, is what got us into so much trouble in the first place.
This brings us back to an aspect of the Anthropocene revolution that is still under debate in the scientific community. When did the new epoch actually begin? Crutzen and others like him who focus on industrial emissions typically choose the mid-to late 1700s as that starting point. Some tie it specifically to James Watt’s development of the modern steam engine in the 1760s.
Others, like climate historian Bill Ruddiman, put it thousands of years earlier. Ruddiman’s idea helps to explain a mysterious anomaly in the record of ancient greenhouse gases that is preserved in air bubbles trapped in deep glacial ice. Ice cores, from Greenland and Antarctica, represent hundreds of thousands of years of climate history, and they reveal an intimate connection between past climates and greenhouse gases. These polar ice records show that while climates have seesawed violently between frosty ice ages and warm interglacials in the past, equally dramatic shifts in carbon dioxide and methane concentrations have also occurred, most of which, as we’ll see in later chapters, had nothing to do with human activity.