In May 2002 the United Nations Environment Programme released a report on environmental trends. The New York Times account stated: “Expansion of cities, destruction of forests, erosion of fields, and rising demand for water are likely to threaten human and ecological health for at least a generation.” The growth of agriculture “is damaging landscapes, depleting aquifers, raising the level of salt in the soil, and reducing habitat for wildlife.” The Times continued, “The report says an important cause is the accelerating growth of vast, poor, and largely unplanned cities in developing countries, most of them near coastlines.”

A month earlier, in April 2002, the New Yorker magazine published an article called “Leasing the Rain.” “The world is running out of fresh water,” the cutline read, “and the fight to control it has begun.” Between 1950 and 1990, worldwide, the demand for fresh water tripled. By 2025 demand is projected to exceed supply by 56 percent. The fight the New Yorker described occurred in “the beautiful old Andean city of Cochabamba, Bolivia,” a city of 800,000 people in which “a good part of the population was now in the streets, battling police and soldiers in what people had started calling la guerra del agua—the Water War.”

Neither fresh water nor arable land is inexhaustible, even in the United States. This fact underscores the need for an agriculture that truly conserves both water and land—and still grows more food to feed the growing cities. The acreage of land under cultivation worldwide has remained the same for almost half a century. Most of the best agricultural land is already being farmed. On balance, additions—such as acres cut out of the Amazon rainforest for subsistence farms—are canceled by the loss of prime farmland to urbanization in some places and to desertification and salinization in others. The miracle of the twentieth century was that the amount of food produced worldwide doubled and tripled, while the amount of land farmed stayed the same. This success had three roots: the genetic modification of plants by professional breeders using many different techniques, the increasing use of synthetic fertilizers invented by chemists, and the improved soil and water management methods devised by agricultural scientists and innovative farmers.

The name Green Revolution was coined by William Gaud, the administrator of USAID. “At the time it was an appropriate description of a momentous event,” writes Gordon Conway in The Doubly Green Revolution. “Today ‘Green’ signifies the environment; then the image it conveyed was of a world covered with luxuriant and productive crops.”

But it is precisely because of the Green Revolution that the world today is not one large farm. Economist Indur Goklany has calculated that if we tried to feed today’s six billion people using the mainly organic farming methods of 1961, we would need to cultivate 82 percent of the earth’s land surface instead of the current 38 percent. The additional acreage amounts to the entire Amazon Basin, the Sahara Desert, and the Okavango Delta, also known as the Okavango Swamp, an area rich in African wildlife. None of these places is best described as farmland.

Norman Borlaug contends that by improving the productivity of existing farmland, the new crop varieties, fertilizers, and farming techniques of the Green Revolution have saved 20 million square miles of wilderness since 1950. Dennis Avery of the Hudson Institute has pointed out that about 16 million square miles of forest exist today. Forests are the first areas likely to be cultivated when farmland ex-

pands (deserts and swamps are not nearly as inviting). “What I’m saying,” Avery told the Atlantic Monthly in 2003, “is that we have saved every square mile of forest on the planet.”

True, the United States currently has a surplus of food, and farmers are paid to take land out of production. But Avery, a former USDA official, has written, “The world has no ‘surplus’ of farmland, in the U.S., in Western Europe, or anywhere else. The world must virtually triple its farm output in the next 40 years. Inevitably, surplus food stockpiled in America means plowing down more wildlife in some other country.” Efforts to protect wildlife and wilderness in other ways will eventually cause conflict. “Nor can we starve the people and let the animals live,” Avery writes. “The people would not go quietly. They would not let their children die of starvation while a wildlife preserve sat unplowed next door.”

Despite conventional wisdom, the modern contraction of agriculture in the United States has environmental benefits. Gregg Easterbrook, profiling Norman Borlaug in the Atlantic Monthly in 1997, labeled the “crisis of ‘vanishing farms’” in America as “perhaps the most environmentally favorable development of the modern age.” He quoted Paul Waggoner of the Connecticut Agricultural Experiment Station as saying, “From long before Malthus until about 45 years ago each person took more land from nature than his parents did. For the past 45 years people have been taking less land from nature than their parents.” And yet, as an article by Jonathan Rauch published in the same magazine six years later pointed out, the percentage of the earth’s land surface that is farmed is still rising: “The increase has been gradual, only about 0.3 percent a year; but that still translates into an additional Greece or Nicaragua cultivated or grazed every year.”

The Green Revolution has had its ecological downside as well. “Pest and disease outbreaks have been an especially severe consequence,” wrote Gordon Conway, due most often to “a combination of factors—higher nutrient levels, narrow genetic stock, uniform continuous planting, and the misuse of pesticides.” Erosion and salinization (from too much or improperly designed irrigation) have also been blamed, often legitimately, on the intensive farming practices of the Green Revolution.

Conway continues: “In the 1960s, when the Green Revolution was beginning to make its impact, little thought was given to environmental consequences. They were deemed either insignificant or, at least, capable of being easily redressed at a future date, once the main task of feeding the world was accomplished. There was also a strongly held view, one still commonly voiced, that a healthy, productive agriculture would necessarily benefit the environment. Good agronomy was good environmental management. It is a point with some force,” he adds. Farmers do need to be environmentalists.

When farming methods are not ecologically wise, Conway argues, “agriculture is both culprit and victim.” In the twenty-first century, the central questions about sustainable agriculture raised by Howard and Rodale and the other pioneers of organic farming remain with us. But are the methods that have come to be called organic—and codified in the Organic Rule—the best we can do?

A hundred years ago when Sir Albert Howard was devising his composting methods, land was not an issue. Between 1870 and 1920 the population increased by 40 percent. The amount of land farmed increased by 75 percent, because more land was cleared, much of it by settlers moving west across North America and by similar expansion in Russia. “The burgeoning populations of those areas were fed by the extension of agriculture rather than by its intensification,” T. F. Evans writes in Feeding the Ten Billion, “while in Europe there was a marked reduction in the proportion of arable land left fallow.”

The human population of the earth was about a billion and a half at the turn of the twentieth century. It is more than six billion today. It is expected to be more than eight billion by 2050. The Great Plains of America and the steppes of Russia are already being farmed. New land could be put under the plow, but arable land is not evenly spread over the globe. More than 90 percent of potential new farmland is in Africa and Latin America. Two countries—Brazil, with 27 percent, and Zaire, with 9 percent—account for more than a third of it. In South Asia, a center of population growth, almost half of the potential farmland is already occupied by cities and towns.

More than half of the people alive today live in cities, with little prospect of growing their own food. By 2020 that proportion will reach

60 percent. They must all be fed. “In 1999 I visited New York City for the first time ever,” plant pathologist Jim Cook of Washington State University recalled in 2003. “I took my wife. We had all our lunches at delicatessens. Thousands of people are eating that way. And the next morning all these delis were full again—ham, turkey, chicken, roast beef. It just came home to me: every night, every city in the world has to refill with food. And none of that food is grown in the city.”

He remembered a visit to an agricultural research center near New Delhi, India. “My hosts drove me out of the city. On our way back, it was getting toward six in the evening. Thousands of trucks were parked along the freeway, stacked so high with boxes that they were top heavy. ‘These trucks have been moving all day long from the north of India, loaded with perishable foods,’ my hosts explained. ‘They can’t get into New Delhi until midnight, the city is too crowded. They have to wait until folk are off the streets.’ At midnight they charge in, unload, then charge out at six in the morning to do it again.”

As Wendell Berry says in his 1981 book of essays, A Gift of Good Land, “We have an unprecedentedly large urban population that has no land to grow food on, no knowledge of how to grow it, and less and less knowledge of what to do with it after it is grown. That this population can continue to eat through shortage, strike, embargo, riot, depression, war—or any of the other large-scale afflictions that societies have always been heir to and that industrial societies are uniquely vulnerable to—is not a certainty or even a faith; it is a superstition.”

Peter Raven uses the concept of the ecological footprint to calculate the impact of today’s population on the environment. Dividing the earth’s 11.4 billion productive hectares by the current world population—6.3 billion people—means that each person has the use of about 1.8 hectares. According to the Worldwide Fund for Nature’s calculations, though, each person in North America uses 9.6 hectares, while each European uses about 5.0 hectares. Only the people in Africa and Asia are living within their means, at 1.3 hectares per person. The worldwide average in 1999, 2.3 hectares per person, is about 22 percent above the planet’s carrying capacity. For developing countries to enjoy the American standard of living, Raven adds, “It would take two planets comparable to the planet Earth to support them.”

Today discussions of farming methods must take into account the environmental consequences of expanding the food supply further. New land put under cultivation is land taken away from the dwindling wildlands that are the planet’s ecological underpinnings—providers of what are called ecological services, such as the underground supply of clean water, climate regulation, and a home for wildlife. If we choose to preserve these, we must ask where the food will come from to feed the still growing human population. If we want everyone to eat as well as today’s average American, we must increase our production of food by more than 400 percent.

Thus our challenge for the twenty-first century is to substantially increase our food supply on roughly the same amount of land in production today while simultaneously ameliorating the impacts of intensive farming and putting it on a sustainable basis. Reaching this goal is likely to require improving every aspect of our current agricultural practices—and inventing new ones as well. Yet Ken Cassman, an agronomist at the University of Nebraska, warns that conventional plant breeding and farming methods are already approaching their maximal yields in some places in the world. Moreover, the extreme polarization of current discussions about organic and conventional farming methods stands in the way of using the best of both. We have few unbiased scientific appraisals of competing methods. Most experimental designs, such as the comparisons of Washington apples or Bolivian potatoes, reflect the belief system of the investigators. The notion that valuable insights can be gleaned from both conventional and organic approaches and combined is almost unthinkable—right now—as is using molecular methods to increase yields and protect crops from diseases and pests.

In a book with the uncompromising title Saving the Planet with Pesticides and Plastic: The Environmental Triumph of High-Yield Farming, Dennis Avery describes a conference of the Organic Farming Association in 1993:

Klaus Ammann, curator of the Botanical Garden at the University of Bern in Switzerland, is among the many who believe a compromise could—and must—be reached between organic farming and the new methods in agriculture. In his long career, Ammann has had many “scientific lives,” as he puts it. He studied the vegetation of alpine and glacial regions. He mapped the flora of all Switzerland. He studied lichens, specifically their chemistry, and came up with a method of using them to monitor air pollution. He studied urban ecology and weeds, consulted with park systems on how to preserve native flora, and did research in the rainforests of Jamaica.

In the 1990s he founded a group called Ecogene to investigate the biosafety of genetically modified plants. The group completed a million-dollar research project on gene flow in Switzerland in 1996 and published their findings on the Internet. In 2003 he produced a report on biodiversity and agricultural biotechnology for the Botanical Garden at Bern. His conclusion is: “We need organo-transgenic crops. We need to make peace with the people in organic agriculture. We need an ecotechnology revolution.”

At the annual meeting of the American Association for the Advancement of Science (AAAS) in 2003, Ammann was asked how scientists could encourage both biotechnology and organic agriculture. He answered, “There’s ideology on both sides. In Europe it’s just cheap marketing to be GM-free. But to build your marketing on a negative has no future. The next generation of transgenic crops may be more interesting to organic farmers.”

Plant pathologist Jim Cook was asked, also at the AAAS meeting, how scientists could encourage biotechnology and organic agriculture at the same time. He replied, “We in the scientific community must never let the divide between the two drive our research.” Cook is an

adherent of sustainable agriculture, although he admits that even this relatively new term has “taken up all sorts of baggage” and become politicized. To Cook it means an agriculture that is dependent on natural biological cycles, one that places a high value on such resources as soil, water, and energy, on the components of fertilizers, and on genetic diversity, and an agriculture that consciously tries to reduce the pollutants—“the dust, sediments, chemicals, gaseous emissions, and other wastes”—that farming releases into the environment. “These objectives must be met,” he stresses, “while continuing growth in the supply of safe, affordable, quality food.” When he says “affordable food,” Cook has in the back of his mind those cities like New York and New Delhi that, each night, must refill their shops with food.

In 2002 the World Resources Institute published Fruits of Progress: Growing Sustainable Farming and Food Systems. It notes that sustainable farming means using “methods that are environmentally sound as well as socially responsible and economically viable. The term ‘sustainable’ farming may include certified organic practices, and also encompasses other ecological and integrated practices.” The publication’s case studies cover four wine producers, seven whose main products are vegetables, fruits, and nuts, and one rice grower. All have incorporated basic ecological principles into their farming methods, the institute says, “such as enhancement of diversity (of crops, varieties, soil biota, etc.), recycling and conservation of resources and nutrients, and reduction or elimination of chemical inputs.” Cook would not argue with any of these goals; yet none of the farmers in the 12 case studies is attempting to produce high yields of a staple crop at an affordable price and on a sustainable basis, as he is.

Cook’s research shows unequivocally that genetically modified crops can contribute to sustainable agriculture. He does not mean virus-resistant papayas or Golden Rice. He means those genetically modified crops most vilified—and least understood—by the press: Roundup Ready soybeans and other herbicide-tolerant crops. He is particularly interested in one that has been developed but not yet marketed: herbicide-tolerant wheat.

For more than 20 years, Cook has been studying no-till agriculture as a way for wheat farmers in the Pacific Northwest to cut erosion and

to enrich the soil. Erosion and soil quality are continuing themes in both conventional and organic agriculture. Yet because the Organic Rule forbids the use of herbicides, organic farmers rely on frequent tilling to control weeds. Why do we plow? As Jonathan Rauch writes in “Will Frankenfood Save the Planet?” published in the Atlantic Monthly in 2003: “Human beings have been ploughing for so long that we tend to forget why we started doing it in the first place.” Before the tractor arrived on the farm, writes T. F. Evans in Feeding the Ten Billion, “The guiding adage was: ‘When the crop stands still, stir the soil.’ Weeds were controlled and soil moisture was thought to be conserved.”

Plowing is one of those practices that historian Mauro Ambrosoli has traced, unchanged, through the farming handbooks published between 1350 and 1850—clear back to the poetry of Virgil from before the time of Christ. But research at the Rothamsted Research Institute in England in the 1930s showed that tilling the soil does not conserve soil moisture and that it is unnecessary if weeds can be kept down by “dust mulches” or some other means. “Indeed ploughing, that hallmark of good farming for more than a millennium, could cause substantial soil erosion,” Evans writes, “as recognized in the Great Plains of the USA during the 1930s when stubble mulching was found to reduce both wind and water erosion.”

Now tillage systems are valued for how much stubble they leave in a field. The best, called conservation tillage, is defined by the Conservation Technology Information Center at Purdue University as “any tillage and planting system that covers more than 30 percent of the soil surface with crop residue, after planting, to reduce soil erosion by water.” Achieving this, however, meant putting up with weeds until herbicides were introduced that were effective enough to replace the plow. The first was atrazine, brought out in 1959. Glyphosate, or Roundup, was “the next major step,” Evans says, when it was released in 1974, being much less harsh than atrazine. “The reduction in soil erosion by minimum tillage can be striking,” Evans writes, “varying from twenty-to a thousand-fold across a range of environments.”

Plowing not only dries out the soil and exposes it to erosion, it releases carbon, as carbon dioxide. Carbon dioxide is a greenhouse gas, suspected to cause global warming. “Carbon disappears faster if

you stir the soil,” Cook explained. “If you chop the crop residue up, bury it, and stir it—which is what we call tillage—there’s a burst of biological activity, since you keep making new surface area to be attacked by the decomposers. You’re not sequestering carbon anymore, you’re basically burning up the whole season’s residue.” In no-till agriculture, on the other hand, the turnover of organic matter happens in such a way that carbon is sequestered. Said Cook, “You’re saving the photosynthate that was manufactured by the plant and returned to the soil as crop residue.”

The organic matter in the soil holds more carbon than is in trees or living plants or anything else on land. It influences the amounts of carbon dioxide, methane, and other greenhouse gases in the atmosphere. Plowing releases carbon into the atmosphere; no-till farming keeps it in the soil.

Plowing also, said Cook, “doesn’t lead to that nice crumb structure we get when we let the process go slowly.” For it is not only the soil’s nutrient content that determines its productivity, but its texture or crumb structure, as Cook named it, which is created by the organisms that live in the soil. Cook was talking not only about earthworms (although a study comparing a plowed field with one that had been farmed for 17 years using no-till methods found more than three times as many earthworms in the no-till field), but about fungi and bacteria. Cook explained, “I think what’s important is the total biomass, not just who’s making up that biomass. You need diversity. You need to have somebody to work in all environments, to have resiliency against stress. The bacteria put out complex carbohydrates that are like glue. The fungi’s threads hold the soil together. When they die, they release nitrogen back into the system. There’s a lot of symbiosis between plant roots and these microorganisms and we only have the slightest understanding of it.”

For instance Dave Weller and Linda Thomashow, Cook’s colleagues at Washington State University, recently discovered that a group of microorganisms, different strains of Pseudomonas fluorescens, can, as Cook put it, “team up with roots to protect them against disease—it’s most interesting. We used to just think the nitrogen-fixing bacteria and the fungal mycorrhizae were the good actors. Here we have another whole world that’s providing benefit to the plant.”

When Cook first became interested in no-till in 1974, it was not a popular way to farm, even though it had been invented by what Cook calls progressive farmers. It is also known as direct seeding, because the seed and fertilizer are placed in the soil at the same time. Notably, the field is not plowed first. Planting involves one pass with a tractor towing a seeder with two tools. Said Cook, “One disk makes a slice, a zone an inch or two wide and three to four inches deep. The second disk is just a little shallower.” The first slice is for liquid fertilizer, with the proportions of nitrogen, phosphorus, and sulfur determined by a soil test. The second disc places the seed.

Direct seeding, Cook said, encourages the growth of soil microorganisms that decompose matter on the surface, “where there is a much more dynamic environment of alternating light and darkness, ultraviolet radiation, and wetting and drying.” When a field has made the transition, as Cook put it, from a plowed field to a direct-seeded field, “the seed-drill goes through the soil easier, and the straw rots faster on the soil surface. The straw that’s left behind with one harvest disappears by the next spring.” It is what he calls “composting in place.” An acre that he has direct-seeded for more than 20 years “is organically as beautiful as it can be. The soil is mellowing out with better crumb structure. You can pull the plow through it in third gear.” In spite of the beauty of the soil in his test plot—and the savings in labor, time, and gas from having to ride a tractor less—Cook finds it has not been easy to persuade either his colleagues or the region’s wheat farmers that no-till is the future of farming. “Farmers are reluctant to change, and so are scientists,” he noted.

The Conservation Technology Information Center reports that in 1991, when Iowa farmers were asked why they didn’t switch to conservation tillage to control runoff and erosion, they answered: weeds. Other surveys of farmers have had the same result. If they knew they could control weeds without plowing, farmers would readily convert to no-till.

The biggest increase in no-till farming since 1996 has come in soybean farming. The center believes it is no coincidence that Monsanto’s Roundup Ready soybeans, genetically engineered to tolerate the herbicide glyphosate, were introduced in that year. In 2001 the American Soybean Association randomly surveyed soybean farmers in 19 states

who planted 200 or more acres. They found that the number of acres being farmed with conservation tillage methods, including no-till, had jumped from 25 to 83 percent. Compared to 1996, more than half the farmers plowed less, while 73 percent left more crop residue in their fields. Why such a change? Sixty-three percent of the soybean growers said, without being prompted, that the reason was Roundup Ready soybeans. They could control weeds in their fields without plowing. In 2002, 75 percent of the soybeans planted in America were genetically engineered herbicide-tolerant varieties, the majority of which were Roundup Ready.

Roundup, for which Monsanto’s patent expired in 2000, was discovered in 1971 by John Franz, a Monsanto chemist. It is now the most popular weed-killer in the world. Every year since 1983 its worldwide sales have topped one billion dollars. It is a broad-spectrum herbicide, meaning that it kills every kind of plant (or as one scientist put it, “essentially anything that is green”), both annual and perennial, grasses and broad-leaved plants. Sprayed on a weed, it is quickly absorbed by the leaves. It moves through the plant, accumulating in the meristems, the growing tips of the shoots. Reaching the chloroplasts, where the plant produces its energy through photosynthesis, glyphosate latches on to an enzyme called 5-enolpyruvylshikimate-3-phosphate or EPSP synthase. This enzyme controls a key step in making the amino acids phenylalanine, tyrosine, and tryptophan. With glyphosate attached to it, EPSP synthase does not work: production of these three amino acids is stopped. Without them, the plant cannot make proteins; it cannot form cell walls, produce hormones, or transport energy. The plant begins to starve. It stops growing, wilts, and turns yellow. Its roots deteriorate, and within a week or two it dies.

Roundup does not harm insects, fish, birds, or mammals (including humans) because none of these creatures have the enzyme EPSP synthase. Unlike plants, animals do not make these three amino acids (phenylalanine, tyrosine, or tryptophan) but instead take them from their food. Fungi and bacteria, including the ones in the soil to which Cook attributes good crumb structure, do contain EPSP synthase. Yet

soil organisms can—and rapidly do—metabolize glyphosate, breaking it down into carbon dioxide and ammonia.

In 1994 Farm Chemicals magazine included Roundup in the “Top Ten Products That Changed the Face of Agriculture” because, they said, Roundup encouraged conservation tillage. Jim Cook agrees. He testified before Congress in 1999, “I can say unequivocally that the development of Roundup as a tool has been the single greatest tool for moving forward to growing crops with less tillage.” Yet it wasn’t a perfect tool to begin with. Glyphosate has no way to distinguish one plant from another, a crop from a weed. So while it could clean a farmer’s fields of weeds before planting, it couldn’t be used while the crop was in the ground. Other herbicides were more specific. Grasses like corn and wheat can tolerate 2,4-D, which mimics the action of the auxin growth hormones. It kills only broad-leaved plants like dandelions. In a soybean field, trifluralin (which inhibits cell division in the roots) can be used; corn sprayed with it, on the other hand, won’t produce a single ear.

Could Roundup be made more specific, made to target only some plants and not all of them? Monsanto’s Ernie Jaworski began working on the idea in the 1970s. “I was just curious about why this chemical killed all plants but didn’t injure animals,” he said when asked how he had gotten the idea for Roundup Ready crops. Steve Padgette, an enzymologist, was hired by Monsanto in 1984. “Jaworski had a clear vision that resistance to glyphosate would be valuable,” he recalled. “He just knew if we could do it, it would work.”

By 1984 Monsanto researcher Ganesh Kishore had identified a change in the enzyme EPSP synthase that would make a plant tolerate Roundup. Said Padgette, “I walked in and started working on petunia EPSP synthase. We were getting some pretty good tolerance but not commercial levels of tolerance. The ‘aha’ moment, for me at least, came in 1986 or ’87. We had a big collection of bacteria that would degrade glyphosate. So we got the idea to screen the bacteria for EPSP synthase. We used a robot. We found one particular bacterial culture in which the extracts showed really good results. It had super high efficiency.”

By the end of 1988 the team had isolated the gene and created a vector with which to introduce it into soybeans. “We were working all

through Christmas getting these vectors ready to go out,” said Padgette. The results were good: “We had soybean transformation.” This gene, from the familiar Agrobacterium, is now found in all Roundup Ready crops: alfalfa, canola, cotton, corn, lettuce, potato, soybean, strawberry, sugar beet, sugarcane, and wheat.

Besides Monsanto’s glyphosate-tolerant varieties, other crops, known by the name Liberty, have been developed that can tolerate being sprayed with a different herbicide, a compound called glufosinate, sold as Basta, Rely, Challenge, and Finale. Like Roundup, glufosinate is a broad-spectrum herbicide, killing all green plants, but its method of action is quite different. Glufosinate was first discovered in a soil organism called a streptomycete, which produces it to poison competing soil microorganisms. Sprayed on a plant, it interrupts the production of the amino acid glutamine, which the plant makes from the nitrates in fertilizers, both natural and synthetic. The nitrates are first turned into ammonia, from which an enzyme called glutamine synthase makes the amino acid. Glufosinate disables this enzyme. The plant cells continue making ammonia until it reaches toxic concentrations. At the same time, having too little glutamine, they can no longer fix carbon. The combination quickly kills the plant.

Because humans and other animals do not use ammonia to make glutamine, glufosinate is not harmful to them. The streptomycete, however, does use ammonia; it has developed a way to avoid poisoning itself. The streptomycete produces an enzyme that attaches an acetyl group onto glufosinate, chemically inactivating it. It can no longer bind to glutamine synthase and so cannot disrupt the production of the amino acid. To make glufosinate-tolerant crops, the gene that allows the streptomycete to inactivate the herbicide was cloned and transferred, using the Agrobacterium method, to crop plants. Canola, chicory, corn, cotton, rice, soybean, sugar beet, tomato, and wheat have all been modified to be glufosinate-tolerant.

A third kind of herbicide-tolerant crop can withstand spraying by imidazolinone herbicides, sold as Patriot, Lightning, On Duty, and other brands. Imidazolinones also interrupt the production of amino acids, in this case leucine, isoleucine, and valine. The enzyme blocked is acetolactate synthase (ALS). When the herbicide binds to ALS, the

enzyme stops working, so the amino acids can’t be made. The plant, unable to produce proteins, dies. The ALS enzyme can readily mutate to a form that is not sensitive to imidazolinone. It takes a change of a single amino acid in the protein’s sequence. For this reason, imidazolinone-tolerant crops can be created without genetic engineering. Those currently on the market, such as corn, canola, rice, and wheat, were created by chemical mutagenesis and somaclonal variation.

Having three kinds of herbicide-tolerant varieties of wheat available to farmers, Cook believes, could give the same boost to conservation tillage in the Pacific Northwest that Roundup Ready soybeans did in the Midwest. Yet so far two of these varieties have stayed on the shelf, the companies choosing not to commercialize them because of political opposition to genetically modified foods. “In Washington, we’re a big wheat-producing state,” Cook explained, “and 90 percent of our wheat is exported. It’s a different kind of wheat than is grown in the Midwest. It’s low protein, only 8 to 9 percent protein. It works well in chapatis and noodles.” Wheat growers have resisted switching to no-till farming using genetically modified crops because, said Cook, “That would make our wheat a GMO, a genetically modified organism, and so far unacceptable to our international customers.”

Wheat that is tolerant of imidazolinone, however, is not genetically modified. “BASF used mutagenesis, old-fashioned mutagenesis,” Cook said. To mutate the gene responsible for the ALS enzyme, BASF exposed seeds to the chemical sodium azide. “It beats up the DNA,” Cook explained. “Some seeds will be dead, others will produce plants with all kinds of morphological changes, and if you don’t like them, you throw them away.” The next step is to spray the healthy-looking seedlings with the herbicide, throw away the ones that die, and continue growing the rest. “You compare them back to your unmodified source,” said Cook. “You look and screen and throw away, and then scale up. You don’t know how many genes have been changed besides the one targeted to make the plant tolerate the herbicide. You don’t have a clue. You might have changed a hundred, or many hundreds of genes. And unless a change can be recognized by looking at the plant, or by watching its performance in the field, it will go undetected.” An imidazolinone-tolerant wheat variety called Above, in the line known

as Clearfield, was released to seed producers by the Colorado and Texas experiment stations in 2001 and by the Oregon experiment station in 2002. Having been conventionally bred and not modified by molecular techniques, these varieties are not subject to federal regulations or international conventions concerning genetically modified foods.

Said Cook, “I’m delighted to see Clearfield come in. I chuckle under my breath to hear that mutagenesis is considered safe and genetic engineering is not, but if that’s what society gives us, we’ll take it.” In the Pacific Northwest, where Cook is located, farmers grow both spring wheat and winter wheat. He can foresee a three-year, no-till rotation using Clearfield winter wheat, Roundup-Ready spring wheat, and Liberty spring barley. Each cereal is herbicide-tolerant, but each has a completely different mode of action to the other two. “It would buy all kinds of durability into the system,” he said. But, he warned, “You need to be careful with Clearfield. That ALS gene is easily mutated.” Already some weeds are resistant. “We’ll see tolerance in four to five years, but if we can then use Roundup Ready or Liberty crops, we can extend its usefulness.”

Cook concluded, “The principle we need to never forget is that diversity is just as important in agriculture as in the environment. This three-year combination would be so efficient you could just skip the herbicide altogether one year—the ground would be so clean.”

Ecologists have taught us that the natural environment provides many essential services: purification of the water and of air, mitigation of droughts and floods, and protection of biodiversity. Asked Cook, “Can’t we do these same things while farming the land? The answer is yes, with no-till. You improve soil structures, stop erosion, sequester carbon, improve water filtration, rather than letting it run off the land, and store more water in years of drought.” The stubble left behind provides habitat for birds and small mammals, which could lead to an upsurge in the number of their predators, including hawks, owls, and coyotes. Compared to conventionally tilled farmland, Cook considers no-till “a whole new ecology” and “a huge step toward being environmentally benign and toward contributing services with social value.” Farmers can achieve these goals, he believes, with a three-year rotation of herbicide-tolerant cereals using three different herbicides—Clearfield, Roundup, and Liberty. But they can’t do it with just one.