The Wizard and the Prophet2

by Charles C. Mann

  Industrial and organic boosters both agreed that soil needed to furnish nutrients to plants, especially nitrogen. The difference was that the Liebigs believed that synthetic fertilizer could deliver them—a nitrogen atom from a factory, they said, was identical to a nitrogen atom from the rear end of a cow—and the Howards believed that they were better provided via the Law of Return as part of a natural system. At the beginning it might have been possible to reconcile the two points of view. One can imagine industrial advocates considering humus, humus advocates willing to use chemicals as a supplement to good soil practice. But that didn’t happen. Hurling insults, the two sides moved ever further apart.

  As early as 1940, Northbourne had described the conflict between organic and conventional farming as a war that would last for “generations of concentrated effort.” Howard was a general in that war—“the warrior at the apex of the phalanx,” one disciple called him. “Chemicalist versus organiculturalist,” Rodale characterized the fight; he was happy to enlist. “The Revolution has begun,” he announced in the first issue of Organic Gardening, capitalizing the R to show that he was serious. The magazine lost money for years. But Rodale was in it for the long haul. McCarrison, Howard, Balfour, Northbourne, and so many others stood at his back. All set in motion a battle that not only continued into the twenty-first century, but with the onset of genetically modified crops became ever more intense.

  Slow

  Picture William Vogt on his guano island in 1940: a footnote in the history of nitrogen. The Haber-Bosch process has been known for thirty years; chemical companies like BASF are capitalizing on it. But natural fertilizer is still important enough that Peru has hired a foreign biologist to protect it. Strikingly, neither scientists nor corporations nor organic advocates understand why it is so important to provide nitrogen to the soil. Not until years after Vogt left Peru did researchers learn the answer: nitrogen is critical to photosynthesis.

  Photosynthesis is hard to describe without sounding like a hand-waving mystic. By blending water from below with sunlight and carbon dioxide from above, photosynthesis links Earth to the sky. The crops in every farmer’s field are air and sunlight in cold storage. So are the trees around the field and the algae in nearby ponds. Every dot of green on the landscape is a ceaselessly active photosynthetic factory. If this furious microscopic churning stopped, Oliver Morton, the science writer, has remarked, “so would everything else that you care about.” The planet would survive. But it would no longer be green.

  Plants need nitrogen chiefly to make a substance called rubisco, a prima donna in the dance of interactions that is photosynthesis. Rubisco is an enzyme, which means that it is a biological catalyst. Like the iron in the Haber-Bosch process, enzymes cause biochemical reactions to occur but are left unchanged by those reactions. Tens of thousands are known—the online enzyme database BRENDA alone has data on eighty-three thousand. Essential to every cell of every living creature, invisible to the eye but feverishly in motion, enzymes typically catalyze thousands of reactions per second. Some accelerate them a billionfold or more.

  Rubisco is the essential catalyst for photosynthesis. Like military recruiters who induct volunteers into the army and then return to their work, rubisco molecules take carbon dioxide from the air, insert it into the maelstrom of photosynthesis, then go back for more. The name “rubisco” was coined, jokingly, in 1979, to sound like a breakfast cereal; it is a sorta-kinda acronym for the compound’s scientific name, ribulose-1,5-bisphosphate carboxylase/oxygenase. Rubisco’s catalytic actions are the limiting step in photosynthesis, which means the rate at which rubisco functions determines the rate of the entire process. Photosynthesis walks at the speed of rubisco.

  Alas, rubisco is, by biological standards, a sluggard, a lazybones, a couch potato. It causes reactions to occur, but very slowly. Whereas typical enzymes catalyze thousands of reactions a second, rubisco deigns to involve itself with just two or three per second. It is one of the pokiest enzymes known. When Warren Weaver bewailed the inefficiency of photosynthesis, he was unknowingly bewailing the torpor of rubisco. Years ago I talked to biologists about photosynthesis for a magazine article. Not one had a good word to say about rubisco. “Nearly the world’s worst, most incompetent enzyme,” said one researcher. “Not one of evolution’s finest efforts,” said another.

  Not only is rubisco slow, it is inept. Carbon dioxide (CO2) consists of a carbon atom (C) flanked by two oxygen atoms (O), the whole in a straight line. Oxygen gas (O2) consists of two oxygen atoms. Like the atoms in carbon dioxide, the oxygen atoms are bound together linearly. Schematically, they look like this:

  Carbon dioxide (CO2, left) and oxygen (O2) Credit 41

  Rubisco is constantly searching, so to speak, for a linear molecule with two oxygen atoms at either end. But as much as two out of every five times, rubisco fails to pick up carbon dioxide, fumblingly grabs oxygen instead, and tries to shove the oxygen into a chemical reaction that can’t use it. To get rid of the unneeded oxygen, plants have evolved an entire secondary process that pumps it out of the cell and re-primes the rubisco to try again for carbon dioxide.

  The mistakes waste energy. Rubisco’s penchant for oxygen reduces the maximum efficiency of photosynthesis by almost half. Because rubisco gets worse at distinguishing between oxygen and carbon dioxide as temperatures rise, the problem is worse in the tropics than in cooler zones. But even in cool climates, wheat harvests would rise by a fifth and soybean harvests by a third if rubisco could distinguish oxygen from carbon dioxide.

  To overcome rubisco’s lassitude and maladroitness, plants make a lot of it. As much as half of the protein in many plant leaves, by weight, is rubisco—it is often said to be the world’s most abundant protein. One estimate is that plants and microorganisms contain more than eleven pounds of rubisco for every person on Earth. The biological chain seems clear: more nitrogen ⇒ more rubisco ⇒ more photosynthesis ⇒ more plant growth ⇒ more food from farms.

  Researchers discovered the import of rubisco in the early 1950s. Almost immediately came a follow-up question: Could scientists develop plants with better rubisco? Was that the way to create faster-growing, more productive, less-fertilizer-intensive wheat, rice, and maize for the coming world of 10 billion? Botanists set to work.

  Here’s the short version of what they found out:

  No—you can’t improve rubisco by any means known then or now.

  Here’s the long version:

  Rubisco is as old as photosynthesis itself. Photosynthesis apparently evolved about 3.5 billion years ago, in the ancestors of today’s cyanobacteria, blue-green, single-celled creatures (the name comes from kyanos, a Greek word for “blue”). For more than a billion years, cyanobacteria proliferated without incident. Then one was engulfed by some microscopic organism, likely a protozoan. Usually this would be routine: the protozoan would be consuming the cyanobacterium as food. But on this occasion the protozoan allowed the cyanobacterium to remain more or less intact—how is unclear—bobbing inside its cell walls. More than that, the protozoan eventually learned how to harness—“enslave” is sometimes used—the cyanobacterium’s photosynthetic abilities for its own benefit. When the altered protozoan reproduced, creating a daughter cell, the cyanobacterium reproduced, too; the two creatures were in a long-term symbiotic relationship.

  This symbiosis was fantastically improbable. In 3.5 billion years of history and trillions of trillions of interactions between protozoa and cyanobacteria it seems to have happened exactly once. But this single incident had huge effects—it is responsible for the existence of plants. Over the eons the cyanobacterium shed many of its original characteristics, and became a chloroplast: the free-floating body in plant cells in which photosynthesis occurs. Plant cells today can have hundreds of chloroplasts, each a descendant of that long-ago cyanobacterium.

  Guffaws greeted this scenario when it was first proposed by Russian biologists in the early twentieth century. Billion-year-old symbiotic entities hidden in
most plant cells? The notion seemed like bad science fiction. In the 1950s and 1960s researchers slowly discovered that chloroplasts have their own, separate DNA; their own, separate genes; their own, separate process for creating proteins. They were like tiny alien beings with a history and purpose of their own. Suddenly the old idea seemed less crazy, at least to Lynn Margulis, who assembled the evidence for ancient symbiosis in a powerful article in 1967. Not only were chloroplasts the result of a long-ago symbiotic event, she said, but so were other objects in cell protoplasm, notably the mitochondria, the minuscule entities that regulate energy flow. In fact, some of the symbiotic protozoan-cyanobacteria associations had themselves been engulfed by other, larger creatures, forming new symbiotic associations. These symbiotic acts were rare, but they had shaped the course of life on Earth. Fifteen journals rejected Margulis’s paper before it was accepted by the Journal of Theoretical Biology. Today it is regarded as a classic.

  At first glance the skepticism seems merited: cyanobacteria typically have several thousand genes that encode the full panoply of molecules necessary for life; chloroplasts have fewer than 250 genes and cannot survive on their own. How could they be connected? The answer is that over the eons most of the cyanobacterial genes have migrated from chloroplasts to the cell nucleus. Among these are some of the genes for making rubisco itself. Rubisco consists of two big subunits, one bigger than the other. The big subunit is encoded by genes in the chloroplast, the small by genes in the nucleus.*5

  This constant genetic shuffle has allowed rubisco to evolve in many ways. Today it exists in at least four main forms, each with several subforms, as well as “rubisco-like proteins” that look like rubisco but have changed to do something else. But despite all the tinkering, no version of rubisco is better at avoiding oxygen than the original. In this respect, 3.5 billion years of evolution has accomplished nothing.

  What evolution seems to be saying, explains Jane Langdale, is that “there is an inescapable trade-off between precision and speed.” If rubisco could better distinguish between carbon dioxide and oxygen, it would be even slower; if it catalyzed more reactions per second, it would make more mistakes. “It looks like there’s a balance—one that hasn’t changed fundamentally for a few billion years.”

  Langdale is a molecular geneticist at Oxford University’s Department of Plant Sciences. When I spoke with her, she had recently been placed in charge of an enormous effort to make an end run around rubisco. Scientists in eight nations were collaborating in an effort to change the way photosynthesis works in rice: perhaps the biggest-ever project in plant sciences. In its effort to hack photosynthesis, the C4 Rice Consortium is an attempt to realize Warren Weaver’s vision of the future—the logical extension of von Liebig’s dream. To Langdale, it is the kind of effort that will be necessary to feed everyone in tomorrow’s crowded, affluent world. It is an attempt to fashion a second Green Revolution. But another way of saying this is that the C4 Rice Consortium is everything Howard and Rodale didn’t want.

  Special Rice

  The Green Revolution had two main branches. One, directly derived from Borlaug’s work, was centered in Mexico at CIMMYT, the research agency descended from the Mexican Agricultural Program. The other was inspired by his work and headquartered in the Philippines, at the International Rice Research Institute. Known as IRRI, the rice institute was initially conceived in the early 1950s, when Warren Weaver and George Harrar traveled through Asia to find out if Asian nations would support a version of the Mexican wheat project for rice. Half a dozen Asian nations promised they would back the new program—but only if it was based on their territory. “That reaction eliminated any hope of creating a research center financed by multicountry contributions,” sighed Robert F. Chandler, IRRI’s first director. Rockefeller was unwilling to pay for the whole project by itself and shelved it. To revive the idea, Harrar and Chandler met with the Ford Foundation. After automobile pioneers Henry and Edsel Ford died, their wills bequeathed so much cash to the foundation that it superseded Rockefeller as the world’s richest charity. The two foundations—one with money, one with expertise—jointly built IRRI on land donated by the University of the Philippines. The campus, sprawling and modernist, was dedicated in 1962.

  At the time at least half of Asia lived in hunger and want; farm yields in many places were stagnant or falling. Governments that had only recently thrown off colonialism were battling Communist insurgencies, most notably in Vietnam. U.S. leaders believed the appeal of Communism lay in its promise of a better future. In consequence, Washington wanted to demonstrate that development could occur best under capitalism. With IRRI, the hope was that top research teams would transform East and South Asia by rapidly introducing modern rice agriculture—“a Manhattan Project for food,” in the historian Nick Cullather’s phrase.

  From the beginning, IRRI’s main plant breeders, Peter R. Jennings and Te-Tzu Chang, focused on developing a rice version of Borlaug’s wheat: fertilizer-responsive, photoperiod-insensitive, disease-resistant, short-straw rice. The task was as daunting for them as it had been for Borlaug, but they had the advantage of being second. Thanks to Borlaug, they knew what the target was and that it had already once been reached. In addition, as it turned out, they were favored by chance—“sheer luck,” Jennings called it.

  Chang, who was from Taiwan, brought to the Philippines three types of Taiwanese rice, curiosities that had short straw but were unproductive and susceptible to disease. Jennings crossbred them with tall tropical varieties, hoping for favorable mixes. It was a comparatively tiny effort: thirty-eight crosses. And the results, Jennings recalled later, “looked terrible.” Combinations of their parents’ worst features, they were all tall, unproductive (most were sterile), and blasted by disease. The best of this unpromising lot produced 130 grains of rice, which Jennings put in the ground with the rest of the seed. In a few of the offspring, the shortness reappeared; some of them also were less susceptible to fungus. These were crossed and harvested; the seed was planted. In the next generation, a single plant in row 233 seemed perfect. Code-named IR8–233–3, grain from that fortunate rice plant was multiplied and planted in test farms all over South and East Asia. It was staggeringly successful. Borlaug’s wheat had doubled or tripled harvests, but the new rice did even better—one trial in Pakistan yielded ten times more than the average of the day. Under the brand of IR-8, the new variety was released to the public in early 1966.*6

  According to its architect, Ralph T. Walker, the modernist IRRI campus, constructed entirely of imported materials, symbolized “a new type of imperialism” of “specialized knowledge generously given to backwards peoples.” Credit 42

  IR-8 was the foundation of the rice wing of the Green Revolution. It was embraced on all levels, by nations big and small, capitalist and Communist, and even by both sides in the Vietnam War. U.S. president Lyndon Johnson visited an IR-8 rice field at IRRI in the fall of 1966 and theatrically crumbled the soil between his fingers while promising to “escalate the war on hunger.” Hoping that “miracle rice” would win Vietnamese hearts and minds by leading peasants to consumer prosperity, his administration set up IR-8 demonstrations throughout South Vietnam. U.S. helicopters dropped pro-IR-8 propaganda leaflets on Vietnamese villages; officials in Saigon, a visitor wrote, were “running around waving IR-8 pamphlets like Red Guards with the Mao books.” North Vietnam fought back by spreading rumors that IR-8 was a U.S. plot to poison villagers. But after the North won the war, miracle rice became the centerpiece of the new government’s brutal rural rebuilding program. By 1980 about 40 percent of the rice grown in East and Southeast Asia was from IRRI; twenty years later, the figure had risen to 80 percent.

  Like Borlaug’s wheat, IR-8 was an essential part of a “package” that included irrigation and artificial fertilizer. Between 1961 and 2003, Asian irrigation more than doubled, from 182 million acres to 407 million acres; fertilizer use went up by a factor of twenty, from 4.2 to 85 million tons. The consequences were drain
ed aquifers, fertilizer runoff, aquatic dead zones, waterlogged soils, social upheaval—and a near tripling of rice production in Asia. Even though the continent’s population soared, Asians had an average of 30 percent more calories in their diet. Millions upon millions of families had more food, better clothing, money for school. Seoul and Shanghai, Jaipur and Jakarta; shining skyscrapers, pricey hotels, traffic-choked streets ablaze with neon—all are built atop a foundation of laboratory-bred rice.

  By 2050, researchers believe, it will have to happen all over again—a second Green Revolution for the world of 10 billion. As a journalist, I have been reporting about population and agriculture, off and on, since the early 1990s. In that time I can’t recall meeting an agricultural researcher who wasn’t worried about what lies ahead. “What is unsure,” IRRI researcher Paul Quick told me not long ago, “is whether that additional demand can be met, and whether it can be met without undue environmental or economic cost.”

  How much will harvests have to rise? Typical projections claim that the world will have to lift food output by 50 to 100 percent by 2050. But in truth nobody really knows, because nobody knows how wealthy the world will be, and what the world’s new middle-class people will want to eat. The biggest part of that uncertainty is how much of their diets will consist of animal products—cheese, dairy, fish, and, especially, meat. In the past, increasing affluence has always led people to eat more meat and less grain and legumes (though there is some evidence that at extreme levels of affluence meat consumption declines). At the beginning of the twentieth century, according to Smil, the environmental researcher, barely 10 percent of the world’s grain harvest went to animals, mostly horses, mules, and oxen used as farm labor. By the beginning of the twenty-first century, the figure had risen considerably, though by exactly how much is difficult to calculate: perhaps 40 percent, Smil estimates, the great majority of it destined for dairy and meat animals.