UNLESS YOU ATTEND a lot of yoga classes or are a Buddhist monk, you probably don’t pay much attention to your breath. We breathe close to 20,000 times per day; if you thought about all the air going in and out, you wouldn’t have time for anything else. But every breath is exceptional. Not only because of the myriad cells and organs that allow us to take it, but also because of what each inhalation contains: 21 percent oxygen, a concentration reached only on earth, as far as we know.
Where that oxygen came from is the subject of Oxygen: A Four Billion Year History by Donald E. Canfield, a professor of ecology at the University of Southern Denmark. Canfield’s strategy is to survey the relevant science and explain it. He does so less as a reporter, making characters of one organism or another, and more as a scientist. Oxygen is far more technical and less narrative-driven than its title suggests — which is actually a good thing. This is the sort of science writing we would all do well to read more of.
If you had asked me before I read this book the origin of our planet’s oxygen, I would have recalled a lesson from high school biology and said, “Cyanobacteria.” Cyanobacteria, or blue-green algae, are the oldest known organisms with the ability to perform oxygenic photosynthesis. That is, by taking energy from the sun’s rays, they are able to combine water and carbon dioxide to produce organic compounds and oxygen. (Although the term “oxygenic” may be unfamiliar, it marks an important distinction: as Canfield explains, cyanobacteria were likely predated by bacteria that used sunlight to transform one sulfurous compound into another, without oxygen as a byproduct; known as anoxygenic phototrophs, they can still be found in hydrothermal pools such as those at Yellowstone National Park.)
While my answer wouldn’t have been incorrect, Canfield persuasively demonstrates that it wouldn’t deserve full credit, either. To cast cyanobacteria as tiny heroes, bringing oxygen and hence multicellular life to this planet, is to fundamentally misread the play. The earth itself is really the starring character — albeit one moving so slowly that most of us aren’t even aware of its role.
Oxygen is the latest volume in “Science Essentials,” a series from Princeton University Press designed to “bring cutting-edge science to a general audience.” While such books often take the form of slick narratives, following a series of characters and the events they precipitate toward a neat resolution, Canfield mercifully departs from the formula, choosing instead to engage with the ambiguity of a world where evidence is imperfect, knowledge evolves, and mistakes can be made in interpreting the data.
Case in point: scientists have long debated the cause (or causes) of the Great Oxidation Event, the substantial rise in oxygen levels that occurred some two billion years ago. Some, playing devil’s advocate, maintain that the GOE represents the evolution of cyanobacteria; from the moment the little creatures arose, the hypothesis goes, they began to reshape our atmosphere. Canfield and a loose network of his colleagues disagree. They argue that cyanobacteria evolved millions of years before the GOE, and that the transition to an oxygen-rich atmosphere has more to do with the slow churn of the earth’s interior than anything else.
To Canfield’s credit, he doesn’t dismiss opposing viewpoints out of hand, or frame them as relics of a benighted time. Rather, he explains what others have argued (and, in some cases, continue to argue) about the GOE, before drawing his own well-reasoned conclusions.
Canfield believes that for hundreds of millions of years, cyanobacteria produced oxygen, only for much of it to combine with other gases in the earth’s atmosphere. Chief among these gases was hydrogen, which reacts with oxygen to form water, and which has been spewing out of volcanoes for eons. Over time, Canfield argues, as the interior of the planet cooled, the rate of hydrogen release slowed, eventually falling below the rate at which oxygen was being produced. And then, presto: oxygen was finally allowed to accumulate in the atmosphere.
“Atmospheric chemistry is a slave to the dynamics of the mantle” — the hot, shifting mass between the planet’s core and crust — “as the interior and exterior of the planet are connected in a profound way,” Canfield writes. Geology, as he lays it out, is crucial not only to the emergence of oxygen on our planet, but also to the fact that so much of it hangs around for us to breathe. While photosynthetic organisms are responsible for introducing oxygen into the atmosphere, they are not the reason that its concentration remains so high. Credit goes instead to a much less visible but no less important feature of our planet: the cycling of sediments, which prevents all of the oxygen that plants and other phototrophs produce from being consumed by chemical reactions.
Most of the organic matter ultimately produced by photosynthesis — including herbivorous organisms and the organisms that eat them — is decomposed by fungi and bacteria, which consume oxygen to do so. If it weren’t for the fact that some organic matter is buried in sediments, where it is compacted into fossil fuels, much of the oxygen that phototrophs release would be prevented from accumulating in the atmosphere by the chemistry of decay; a coal deposit, in other words, actually represents a net oxygen source to the environment.
The other main source of oxygen — perhaps more important hundreds of millions of years ago, Canfield says, than the burial of organic matter — is the burial of pyrite, or fool’s gold. Pyrite is formed from hydrogen sulfide (the gas that gives rotten eggs their characteristic odor), a small amount of oxygen, and iron. If that hydrogen sulfide is the product of sulfate reduction — a process whereby bacteria decompose organic matter without using any oxygen — the burial of pyrite allows oxygen that would otherwise be consumed by decomposers to remain in the atmosphere. (The oxygen cycle is completed when buried sediments are eventually unearthed and oxidized, a process that, in Canfield’s estimation, takes two to three million years.)
“A sparse geologic record, combined with uncertainties as to its interpretation, yields only a fragmentary and imprecise reading of atmospheric oxygen evolution,” Canfield has written elsewhere. Be that as it may, the role that the earth plays in regulating the life that inhabits it seems clear: we are, all of us, from microbes to humans, the beneficiaries of geological and chemical processes so vast that to contemplate them is to realize that an act as simple as breathing could hardly be more complex.
Canfield reassures us that, despite all the changes that humankind is wreaking on the environment, our oxygen is in no danger of going away anytime soon. This is a relief, as the same cannot be said for the stable climate in which civilization has arisen. Climate is closely tied to the carbon cycle, the process by which carbon moves between the earth, sky, and sea. The burning of fossil fuels has perturbed the cycle. Carbon that otherwise would have taken millions of years to leak out of the earth, via volcanoes, has been liberated in fewer than two centuries. Because carbon dioxide (the gaseous form that most of the carbon in the atmosphere takes) absorbs and radiates heat, our activity has turned up the planetary thermostat, with consequences that are becoming increasingly hard to ignore.
Last year, the Australian Bureau of Meteorology had to add two new colors — deep purple and pink — to its heat index, to indicate temperatures above 122 degrees Fahrenheit. Los Angeles just experienced its driest year since record-keeping began in 1877. Owing to an unfortunate coincidence of subsiding land and rising sea, some streets in Norfolk, Virginia, are routinely flooding under the full moon. And, as The New York Times reported in January, a draft report from the United Nations has concluded that “another 15 years of failure to limit carbon emissions could make the problem virtually impossible to solve with current technologies.”
So, what’s a person to do?
Bill McKibben, the longtime environmental writer and now activist, offers two answers in Oil and Honey, his most recent book. One is to build a movement to put the brakes on our ever-increasing consumption of fossil fuels — no easy task, McKibben acknowledges, as the business of extracting and selling fossil fuels is the most profitable enterprise in the history of money. And yet, as his absorbing account of the transition from writing to activism makes clear, battles can be won — or, at the very least, prolonged. If not for the work of 350.org, the organization that McKibben and a handful of his students at Middlebury College founded in 2008, the Keystone XL pipeline, which would tap oil from Canada’s tar sands and possibly lead to a significant increase in greenhouse gas emissions, would have likely been completed already.
McKibben is perhaps best known for The End of Nature, his 1989 book that was among the first to introduce global warming to a general audience. In Oil and Honey, he explains, “[M]y initial theory (I was still in my twenties) was that people would read the book — and then change.” Needless to say, not enough people did, so he kept on writing — he has since authored or edited more than a dozen books. And yet, that, too, wasn’t enough. “Sometime over the course of the last decade,” McKibben writes, “I figured out I needed to do more than write — if this fight was about power, then we who wanted change had to assemble some.” And thus McKibben, by his own admission a mild-mannered Methodist more at home in his study than onstage, set out to launch a movement.
McKibben has written some fairly wonky books — this isn’t one of them. Oil and Honey is largely a memoir. The book chronicles two years of his efforts, from 2011, when he organized his first protest against Keystone XL, at the White House — an act of civil disobedience that lasted two weeks and got more than 1,200 people (including McKibben) arrested — to 2013, when he toured the country to pressure universities to divest their portfolios of fossil fuel stocks (a tool used in the 1980s against companies doing business in South Africa to sanction apartheid).
Taking us behind the scenes as he plans protests, gets arrested, and butts heads with political operatives, McKibben charts a gripping narrative. He makes clear that the obstacles he’s surmounted so far were hardly gimmes. When a bill to approve the pipeline came up in the Senate in 2012, he recalls, the American Petroleum Institute was so sure of the bill’s passage that it sent out a press release during the vote, congratulating the Senate on “taking a bold step.” After the bill lost by two votes, the API corrected the release, noting that the body “had tried to take a bold step.”
At such moments, a cheer may escape the reader’s lips. Each victory — and there’s more than one — is owed not only to McKibben and his team at 350.org, but also to the many volunteers he describes beavering away, sending emails, organizing demonstrations, staging lectures, and putting their bodies on the line. McKibben shares a DC cellblock at one point with Gus Speth, the head of President Carter’s Council on Environmental Quality and a retired Yale dean, who gives the following statement to the press: “I’ve held a lot of important positions in this town, but none seem as important as this one.”
Of course, as McKibben readily concedes, “environmentalists never win permanent victories.” This is especially true of the seemingly interminable grind of fighting global warming in Washington. McKibben wryly notes, “[T]he negotiation was between human beings and physics, and physics wasn’t going to bend.” Some concerned observers have taken matters into their own hands. In 2012, Russ George, a California businessman, dumped 100 tons of iron dust into the Pacific Ocean off western Canada, hoping to spur the growth of phytoplankton and reduce the amount of carbon dioxide in the atmosphere. In Oil and Honey, McKibben reveals that he, too, has hedged his bets, albeit with a less extreme gesture: he has attempted to build a farm.
In the fall of 2001, not long after he started teaching at Middlebury, McKibben met Kirk Webster, a local beekeeper. After inviting Webster to lecture in a course on local food production, McKibben kept in touch. Years later, aware that Webster wasn’t making enough money from his apiary to buy land, McKibben offered him a deal: in exchange for building a farm and getting it running, McKibben would buy the farmland and grant Webster free lifetime tenure on it. “I’ve always wanted something to leave my daughter,” McKibben writes. “Given what I knew about climate change, the gift of productive land seemed like the best thing I could hope to pass on to her, an insurance policy worth more than money in some account.”
The farm provides McKibben a break from his hectic schedule and gives his narrative a foil. Compared to our maddeningly intransigent and obstructive Congress, the bees — whom McKibben helps Webster manage despite being allergic to wasp stings (he carries two EpiPens on hikes) — are cooperative and reasonable. When a colony leaves its hive to search for a new home — an act known as “swarming” — scouts return with information to take part in a debate that, although conducted by thousands of bees hanging from a tree branch, sounds a lot more civil than much of what happens in Congress.
McKibben reports that each scout does a dance, its vigor depending on how well the bee believes the location it found will fit the colony. After a while, the scouts gravitate toward one dance or another — apparently, apiarian voting looks a lot like Soul Train — at which point the swarm carries the queen (who hasn’t participated in the decision-making process) to her new home. This sort of frank debate, McKibben aptly notes, is sorely lacking among politicians: “It’s hard to imagine a hive that would, say, go over a fiscal cliff of its own making.”
McKibben writes at the outset that he doesn’t intend to prescribe his responses to climate change — activism and farming — to his readers. But, at least when it comes to farming, he flatly contradicts himself. “This new operation would not change the world,” McKibben writes of the farm, “both [Kirk and I] knew that. But it would, you know, change the world. The sum total of a million of these kind of small shifts would be a different civilization, one you could just begin to sense emerging as farmer’s markets spread across the nation.”
While an America of small farmers certainly would be different, it wouldn’t necessarily be better. David Owen, a New Yorker staff writer, has persuasively argued that, in some respects, dense urban areas like New York City are more friendly to the environment than rural ones. Although population density is often taken as an environmental ill, it’s actually not so bad. “If you made all eight million New Yorkers live at the density of my town,” Owen, who lives in rural Connecticut, wrote in 2004, “they would require a space equivalent to the land area of the six New England states plus Delaware and New Jersey.” Rather than encouraging waste, cities limit it: if you live in a place where traffic is horrendous and space is at a premium, there’s every reason not to own a car or buy lots of big appliances, whereas if you live far from an urban center, you have lots of space to fill and need to drive just about everywhere.
Perhaps McKibben envisions a nation of Kirk Websters: people who use “just enough fuel to get the pickup between beeyards.” That’s a nice idea, but the likelihood that our culture, as McKibben describes it — “one that depends on more, on faster, on ambition, on a kind of generalized horniness for accumulation and sensation and novelty, novelty, novelty” — will voluntarily content itself, as Webster does, with sitting alone in a small house with a handful of books and no consumer electronics seems remote, at best.
What’s more, it’s hard to argue that the massive problems we now face aren’t the product of extremely rational short-term decisions. As Webster and McKibben, perhaps unintentionally, make clear, fossil fuels have been an enormous boon, at least for those who’ve been able to avoid their pernicious side effects so far. Early on, Webster buys a tractor, in order to, among other projects, dig a conduit for electrical cables. “It only took a day and a half in the tractor,” he says. “You understand why fossil fuel can be a good thing.” McKibben chimes in later, when Webster articulates his dream of using animals to work the fields. “For me, though,” McKibben writes, “I was deeply happy with the tractor.”
McKibben speaks from time to time with dismay about the way that climate change is disrupting the familiar patterns of life on earth — altering the flowering cycle, prompting bees to begin foraging for nectar earlier; allowing tick populations to bloom year-round, contributing to a massive decline in the number of moose. At one point, he writes of the way things should be: “I lay back in the sun in my bee veil, listening to the thrum of bees that filled the air, and behind it the background note of the crickets’ song swelling and falling: the comforting sound of life on automatic, the planet working as it should.” But, to judge by Canfield’s book, the notion that our planet should be one way or another seems short-sighted.
What McKibben takes here as normal — a planet teeming with a diversity of life, ranging from bees and crickets to the humans contentedly observing them — is a historical anomaly. The fossil record seems to indicate that, for billions of years, the earth was without appreciable amounts of oxygen, and could support only microbial forms of life. And yet, that world was perfectly natural, too.
Nature is often spoken of as if it were immutable. If only we could go back to nature, we say, as if it were an Eden that our activity had exiled us from. But nature is not so easily defined. If we were to go back to nature, where would we stop? The effect that organisms have on their environment has always been part of nature — indeed, it has shaped what we think of as natural.