The Wizard and the Prophet2

by Charles C. Mann

  Could natural systems (or natural-feeling systems) be harnessed to suck carbon from the air? Why not create a new Carboniferous by covering the two biggest deserts in the world—the Sahara and the Australian outback—with trees? In 2009 three researchers—two at the NASA Goddard Institute for Space Studies, one at the Mount Sinai School of Medicine, all in New York—proposed just that. At bottom, the idea is easy to understand. Very roughly speaking, humankind emits 40 billion tons of carbon dioxide a year, mostly by burning fossil fuels. About 40 percent of the total is absorbed by plants, microorganisms, and the ocean. Foresters have spent decades measuring the rates at which trees grow, which in turn is a measure of their capacity to take carbon dioxide out of the air. If one takes foresters’ measurements seriously, covering all 3.8 million square miles of the Sahara with drought-tolerant Eucalyptus grandus would suck roughly 20 billion tons of carbon dioxide from the atmosphere every year—enough to have a substantial impact on climate change, though its exact size would depend on the reaction of the oceans and land plants. Still more carbon dioxide could be tucked away by foresting the Australian outback, which is almost two-thirds the size of the Sahara.

  Tree planting, advocates say, is simpler and less risky than high-tech Wizardly schemes. Instead of building costly carbon-capture facilities and nuclear plants, people should install cheap, natural carbon-eating mechanisms—trees—in equatorial deserts. Unlike carbon-capture plants, trees in carbon farms represent a direct solution to the problem of climate change. Adding sulfur to the air, geoengineer-style, would make the world less hospitable by harming the ozone layer. Planting trees in the Sahara, the Arabian desert, the Kalahari, or the Australian outback would make these parts of Earth more habitable, even desirable. The trees would increase humidity, which in turn should increase rainfall. Land that is now sterile would become farmland for carbon, and then, possibly, just farmland.

  All climate-change measures will involve people in developed nations paying a lot of money, Klaus Becker and Peter Lawrence of the University of Hohenheim, in Stuttgart, have contended. Now present those taxpayers with two alternatives, “one that requires the introduction of untried and potentially hazardous new technology on their own doorsteps, and one that involves the establishment of forests in underpopulated countries far away with possible related benefits for the local populations.” Potently combining the virtues of altruism and Not In My Back Yard, carbon-farming is more politically feasible, from this perspective, than either carbon capture or nuclear power.

  To get an idea of what a massive reforestation project might be like, visit the Sahel. Technically, the name “Sahel” refers to the arid zone between the Sahara Desert and the wet forests of central Africa—a broad east-west band that runs from Mauritania on the Atlantic through Burkina Faso, Niger, and Chad to Sudan on the Red Sea. Rhetorically, “Sahel” is a watchword for famine and desertification. Until the 1950s the Sahel was thinly settled. When the population boom began, people from the more crowded areas to its south shifted north, into the empty zone. Like city slickers moving into the sticks, they didn’t know how to work this dry land. In the 1960s problems were masked by unusually high rainfall. Then came two waves of drought, one in the early 1970s and a second, worse episode in the early 1980s. More than 100,000 men, women, and children died in the ensuing famine—probably many more.

  In Burkina Faso, an aid worker named Mathieu Ouédraogo assembled the farmers in his area to experiment with soil-restoration techniques, some of them traditions that Ouédraogo had read about in school. One of them was cordons pierreux: long lines of stones, each no bigger than a fist. Because the area’s rare rains wash over the crusty soil, it stores too little moisture for plants to survive. Snagged by the cordon, the water pauses long enough for seeds to sprout and grow in this slightly richer environment. The line of stones becomes a line of grass that slows the water further. Shrubs and then trees replace grasses, enriching the soil with falling leaves. In a few years, a minimal line of rocks can restore an entire field. As a rule, poor farmers are wary of new techniques—the penalty for failure is too high. But these people in Burkina were desperate and rocks were everywhere and cost nothing but labor. Hundreds of farmers put in cordons, bringing back thousands of acres of desertified land.

  Yacouba Sawadogo, 2007 Credit 75

  One of the farmers was Yacouba Sawadogo. Innovative and independent-minded, Sawadogo wanted to stay on his farm with his three wives and thirty-one children. “From my grandfather’s grandfather’s grandfather, we were always here,” he told me. Sawadogo laid cordons pierreux across his fields. He also hacked thousands of foot-deep holes in his fields—zaï, as they are called—a technique he had heard about from his parents. Sawadogo salted each pit with manure, which attracted termites. The insects dug channels in the soil. When rain came, water trickled through the termite holes into the ground, rather than wash away. In each hole Sawadogo planted trees. “Without trees, no soil,” he said. The trees thrived in the looser, wetter soil in each zaï. Stone by stone, hole by hole, Sawadogo turned fifty acres of desert waste into the biggest private forest for hundreds of miles.

  To my untrained eye, his forest looked anything but miraculous: an undistinguished tangle of small trees and shrubs interspersed with waist-high grass. Then Sawadogo showed me a photograph of his land at the time of the drought: bare reddish soil, tufts of grass, a few dusty bushes. Hardly a tree was in sight. For me to think his land looked undistinguished was like looking at a functioning automobile somebody built out of junk in the basement and sneering at the paint job.

  Using little but rocks and shovels, farmers in broad stretches of the Sahel have restored savanna forests like this one in Burkina Faso. Comparing this area with what had been the same spot just a few years before (photo in picture) provides vivid evidence of the power of reforestation to change landscapes rapidly. Credit 76

  At his home Sawadogo had a list of the tree species in his forest, compiled by a botanist in Ouagadougou, the capital. Atop the list was Jatropha curcas, a small, shrubby tree with nuts used to make fuel oil. In 2014 German researchers dug up jatropha trees from Luxor, Egypt, and measured their carbon content. They determined that an acre of desert jatropha warehouses the carbon from 209.5 tons of carbon dioxide every year. On average, each U.S. citizen emits 18.7 tons of carbon dioxide per year; each German, 8.9; each Indian, 1.7. If jatropha carbon-storage values are typical, walking through Sawadogo’s fifty-acre tree farm was like pushing through a crowd of 560 Americans, 1,175 Germans, or 6,160 Indians.

  Unsurprisingly, the new techniques, uncomplicated and inexpensive, spread far and wide. The more people worked the soil, the richer it became, the more trees grew. Higher rainfall was responsible for part of the regrowth (though it never returned to the level of the 1960s). Another contributing factor, possibly, was higher atmospheric carbon-dioxide concentrations—they make rubisco’s job easier. (A big study in 2016 suggested that as much as half of the world’s vegetated area was becoming somewhat greener, with increased carbon-dioxide levels responsible for most of the additional growth.)*13 But mostly the restoration of Burkina was due to the efforts of individual men and women. Next door in Niger was even greater success, according to Mahamane Larwanou, a forester at Dioffo University in Niamey. With little or no support or direction from governments or aid agencies, local farmers used picks and shovels to reforest more than forty thousand square miles, an area the size of Virginia.

  The carbon farms envisioned by Prophetic geoengineers are much bigger and located in even drier areas. Initially, they would require irrigation. In many cases the water would have to come from desalination plants on the shore. At first the plants would probably run on solar energy; after about three years, they could be driven by trimmings, leaves, and nuts from the trees. Studies suggest that trees could provide enough power to provide their water—they would be, so to speak, sustainable. After several decades, carbon farmers would harvest the trees and replace them with new, fast-growing
saplings. All of this would be expensive, but all carbon remediation schemes are expensive. It is not ridiculous to imagine that the economic activity from making the Sahara habitable would offset some of the costs.

  The old trees could be “pyrolized”—burned in low-oxygen environments, which turns them into charcoal. Depending on how it is produced, charcoal typically retains about two-thirds of its original carbon. The charcoal can be ground and buried, enriching the soil. Desert soils tend not to hold nutrients and organic matter because they are made from types of dirt that don’t bind to them chemically. Any precipitation makes them wash away. Over time, buried charcoal slowly oxidizes, providing the requisite binding sites. Nutrients and organic matter “stick” to it, providing food for the bacteria, fungi, and other microorganisms that make soil fertile. Charcoal, properly manufactured and deployed, can dramatically improve bad farmland. It also stores carbon: Johannes Lehmann, a charcoal-soil expert at Cornell University, has calculated that turning residues from agriculture and logging could offset as much as an eighth of the world’s carbon dioxide output if the gases from charcoal-making were captured and turned into fuel. The figure is higher if the climate-changing gases methane and nitrous oxide, emitted by rice paddies and fertilizer, are included. Presumably these techniques could be applied in carbon farms.

  Typically Wizards react to these scenarios by pointing out their unfeasibility. The forests would destroy desert ecosystems, they say. Or they would require large numbers of people to radically change the way they live. Or it amounts to green imperialism—forcing poor people in desert areas to offset the emissions of faraway rich people. These criticisms are a distorted mirror of the Prophetic criticisms of Wizardly ideas. Prophets are appalled by the top-down nature of CCS and nuclear power, which depend on unelected technical experts. They like reforesting, which functions best when it is bottom-up, harnessing the willing participation of people like Yacouba Sawadogo. Either one must coordinate the actions of millions of people to have an impact or create processes that need so few people that they can’t be controlled.

  What to do, in a world brimming with fossil fuels? In climate change, all choices involve leaps into the unknown. Claims that carbon capture cannot be economically viable or that renewables will always cost too much or use too much land generally amount to saying, I prefer the unknown risks associated with this course rather than the unknown risks associated with that course because the first leads to a future that I like better. At bottom, the choices stem from private images of the good life—a life in which people are tied to the land or free to roam the skies. Only individuals can choose. The important thing is that they have choices, and we are still at the stage where, however dimly, we can imagine that Lynn Margulis was wrong.

  * * *

  *1 As I mentioned in the Prologue, I am splitting the discussion of climate change into two pieces. Here I ask skeptics to accept—just for the moment—that climate change is a problem, so I can look at how Borlaugians and Vogtians would address it. In an appendix, I address whether one should believe in its potential impact.

  *2 It is often said that Fourier discovered the “greenhouse effect.” This is wrong for two reasons. First, Fourier never said the atmosphere acts like a greenhouse—the term serre (greenhouse) doesn’t appear in his articles. Second, the atmosphere doesn’t act like a greenhouse. The atmosphere is warm because it absorbs heat radiation from the surface. A greenhouse is warm because the glass physically blocks hot air from wafting away, a different process. Because many scientists whom I spoke with regard “greenhouse effect” as misleading, I avoid it in this book.

  *3 Three years before Tyndall, a U.S. scientist published a two-page paper that described how different gases absorb solar energy. The scientist was Eunice Foote, a suffragist from upstate New York. Little is known about Foote; she published just one other article, on a different subject, and no further trace of her work has been found. Foote’s research was similar to but less comprehensive than Tyndall’s work. No evidence exists that Tyndall knew of it.

  *4 Today we know that is because an atom’s electrons surround it in complex “orbitals.” An atom can absorb an incoming light wave only if it has exactly the right energy to kick the atom’s electrons from one orbital to another, more energetic orbital. Any more or any less and the atom won’t take it in, because the light wave’s energy doesn’t match the energy between orbitals. All of this baffled nineteenth-century physicists: How could atoms be so choosy? Resolving the puzzle led in the early twentieth century to the revolution of quantum mechanics.

  *5 Most researchers now think that the ice ages were caused by slight shifts in the earth’s tilt and orbit, which changed the amount and distribution of sunlight on the surface, cooling the planet.

  *6 About radiocarbon dating: Earth is constantly bathed by a rain of high-energy subatomic particles from outer space. When these “cosmic rays” slam into a carbon atom, they knock away bits of its nucleus. This creates a trickle of mildly radioactive carbon: carbon-14 (14C), as scientists call it. By happenstance, 14C disintegrates into a form of nitrogen at almost exactly the same rate that it is created by cosmic rays. As a result, a small, steady percentage of the carbon in the air, sea, and land consists of 14C. Plants take in 14C through photosynthesis. When animals eat plants, they take it in, too. In consequence, every living cell has a steady, small level of 14C—they are all slightly radioactive. When organisms die, they stop absorbing 14C. Because the 14C in their cells continues to disintegrate, their bodies’ 14C level falls in a predictable way that researchers can use to estimate when the creatures were alive. Suess realized that carbon dioxide from burning petroleum would have almost no 14C because the organisms that had created it had died millions of years ago. It would thus be possible to detect if fossil fuels were pumping this 14C-less carbon dioxide into the environment—the overall 14C level would be a hair lower than it would be otherwise.

  *7 Feedback in this sense occurs when the output of a system gets fed back into the system, affecting the next output. An example is the way an opera audience’s bravos can affect the performers. If the crowd cheers every time a soprano stops the show with a high C, the singer might, buoyed by approval, try to hit more high Cs. Enough feedback, and the performance will be nothing but flashy high notes. This is positive feedback: the feedback increases the change until it reaches a new state. If the audience boos, the soprano might not try any more high Cs and just sing normally—negative feedback, when the feedback reduces the change. The back-and-forth between singer and crowd is a feedback loop.

  *8 The ozone hole, discovered in 1985 by British researchers, was a severe regional drop in the stratospheric “ozone layer” that absorbs the sun’s harmful ultraviolet radiation. Nuclear winter referred to the risk that a nuclear war could throw enough dust and smoke into the atmosphere to block the sun, creating a years-long winter of the sort familiar to readers of A Song of Ice and Fire. Acid rain was created when sulfurous air pollution from power plants combined with water vapor to form airborne sulfuric acid, which could mix with rain and fall on distant places, damaging lakes, streams, and forests.

  *9 Where do these numbers come from? Researchers have constructed half a dozen large climate models. These simulations are made of thousands of relations, each with measures of uncertainty—statements that if X happens, it will have an effect on Y of magnitude a, b, or c. When researchers run the simulation, the computer randomly goes through every imaginable variation—every a, b, or c of every relation—to obtain all possible outcomes. In this case, about two-thirds of the time that outcome is a temperature rise of between 2.7°F and 8.1°F.

  *10 Because many electric plants have several power-producing facilities, the number of coal units is about 8,800, of which about 6,700 are bigger than thirty megawatts (an average U.S. coal plant is more than five hundred megawatts). No good census of the world’s coal-fired steel mills or cement plants exists. “Several thousand” is an estimate from the World Steel As
sociation and the Portland Cement Association. Still, the point remains: compared to oil and gasoline, coal is burned in a small number of facilities.

  *11 The storage part of the equation is more straightforward. Engineers like to say that “nature is the proof of concept.” What are petroleum fields but natural storage sites for carbon? Recall that a petroleum deposit consists of two layers of stone, a porous bottom layer beneath a non-porous cap. Carbon dioxide storage is the reverse of oil drilling: companies pump pressurized carbon dioxide through impermeable rock into permeable rock. After the rock is filled, the entrance hole is plugged forever, a reliquary for humankind’s energy obsession. In principle, carbon dioxide could be tucked into such lairs until the sun explodes. In practice, it needs to be stored only for a century or so, the time required for the carbon dioxide to combine with the surrounding stone and form stable minerals. Most scientists believe this to be an achievable goal.

  *12 Wizards and Prophets mostly agree on energy conservation—making buildings, vehicles, and machinery waste less energy. For this reason I don’t discuss it, but efficiency is key to any climate strategy. The more energy you don’t use, the less you need to convert from fossil fuels.

  *13 At a certain point, the benefits of higher carbon-dioxide levels to plant growth are outweighed by the negatives, including drought, heat stress, and enzyme failure. The exact line varies from species to species. For rice the limit may be quite low, because at just slightly higher temperatures than usual it can’t produce fertile pollen.

  TWO MEN

  [ EIGHT ]

  The Prophet

  Launch

  Washington, D.C., 10:00 a.m., December 27, 1947. A thousand feet, give or take, from the Lincoln Memorial. Boardroom of the U.S. National Academy of Sciences: walnut-panel walls, Persian carpet, marble fireplace, massive oil painting of a stone-faced Abraham Lincoln signing the academy charter. Pale winter light through the shades. A long oval table, gleaming in that light. Above the table a spherical glass light fixture, an electrolier, painted to resemble the map of the world drawn (or thought to have been drawn) around 1515 by Leonardo da Vinci. Bathed in its yellow glow: a huddle of men in dark suits and white shirts. High officials from the U.S. Department of the Interior, the Department of Agriculture, the National Research Council—and two civilians. The first civilian is William Vogt, head of the Conservation Division of the Pan American Union. One imagines him nervous and quietly excited to be in this room, literally in the meeting before the meeting, surrounded by people whose hands rest comfortably on the levers of power.