Schrank, a So Paulo grower who recently destroyed 12,000 stricken trees, there’s another name for it. “This”–he nods at a stretch of bare dirt, as red and raw as a wound–“this is like AIDS.”
Actually, it’s more like tristeza da laranja (“the orange’s sorrow”), a virus that ravaged the Brazilian countryside in the 1940s. In a few years, the disease killed all varieties of Brazil’s orange trees except one: the limo cravo. Brazilians hailed the limo cravo as something of a miracle, and farmers made it the foundation crop of the orange industry’s renewal. Of course, they knew–as farmers everywhere know–that planting only one kind of anything is folly. History is rife with single-crop catastrophes, from the locust storms of Biblical Egypt to the Irish potato famine. But they risked it anyway. By the late 1990s, Brazil had overtaken the United States in orange production. Today, 85 percent of Brazil’s 200 million orange trees are grown from limo cravo rootstalk. In an ironic twist, scientists believe that the new virus may be a relative of the orange’s sorrow, returned to claim the one tree spared in the previous epidemic. Says Nelson Gimenes, a plant pathologist at research lab Fundecitrus, “The risk of catastrophe is enormous.”
Ever since hunters and gatherers swapped spears for seeds, farmers have waged war with germs and pests. Usually, producers have prevailed over the pathogens. But today the stakes are infinitely higher. Old-style farms, with a mosaic of different vegetables, fruits and cereals grown on a single plot, weren’t terribly efficient, but the diversity of crop types helped insure against catastrophic losses due to disease. In the rush to feed the world’s billions, diversity has been sacrificed on the altar of efficiency. Agriculture is now an industrial-scale enterprise, with huge estates dedicated to the cultivation of a single crop–so-called monoculture farming.
Today, fewer and fewer farmers produce massive quantities of super crops that smother the land in a seamless carpet. Intensive irrigation and synthetic fertilizers pump up yields. But these vast spreads are sitting ducks for pests and pathogens, which farmers fight with ever-growing doses of insecticides and weed killers. The most powerful new tools to defend the gains of the green revolution–namely, genetically modified crops–are taboo in many nations. That leaves farmers with a handicap. If some kind of solution isn’t found, many scientists say, food crises will grow more frequent and disruptive. Eventually we may find that the food supply we take for granted may falter. “How long will it take before we have an ecological disaster?” says David Tilman, an ecologist at the University of Minnesota and a longtime scholar of monoculture farming. “We –can’t afford to have a SARS in agriculture.”
The green revolution, based largely on monoculture farming, saved much of the world from the threat of starvation due to overpopulation–at the expense of diversity. According to Jared Diamond in the journal Nature, the first farmers chose from 200,000 species of wild plants and 148 wild animals, but today only 100 plant varieties and just 14 different animals are routinely cultivated–the ones that humans could most easily tame, reproduce, manipulate and profit from. Orderly expanses of a single crop like wheat or soy are convenient to plant and reap, and make big profits for breeding companies, which can sell tons of super seeds. Streamlining the garden has long been the most efficient way to put food on an ever larger number of tables.
It still is, but the gains have begun to falter. From sprawling Kansas wheat fields to southern China’s rice fields, farmers do almost daily battle with legions of microscopic enemies: blight, bunt, blast and bugs that rip through their fields like fire through kindling. In the United States, pests and diseases devour $90 billion worth of food crops a year. Worse, these ills hitch rides around the globe aboard ships, airplanes and trucks, stuck to the soles of shoes or merely riding the winds. Customs keepers and health inspectors do a heroic job of holding the invaders at bay, but their efforts are laughable. U.S. port officials intercept some 13,000 exotic plant diseases every year, but check only 2 percent of incoming freight, according to a National Academy of Sciences report.
If mobility makes germs more dangerous, monoculture makes farmers more vulnerable. Like families, single-crop plantations are stamped with nearly identical genes. “If there is an inherited defect, all of the siblings are vulnerable,” says Zhu You-yong, a plant pathologist at the Phytopathology Laboratory in China’s Yunnan province. “We may not be able to see it now, but in the future monoculture is going to be a threat to the world food supply.”
The dark side of monoculture is becoming more and more apparent. When southern corn-leaf blight tore through the one-of-a-kind corn farms in the 1970s, U.S. farmers tallied $1 billion in damages. Late potato blight, a cousin to the fungus that devastated Ireland, is even more intractable today than two centuries ago, costing potato plantations $2.7 billion a year worldwide.
For small farmers, the impact of disease can be even more devastating. In the vast and populous Indian states of Uttar Pradesh, Bihar, West Bengal and parts of Assam, rice cultivators plant almost nothing but the Mahasuri variety, leaving them wide open to disease. Chinese peasants lose 10 percent of their harvest to rice blast, while wheat rust claims 20 percent of their grain. And while North American potato potentates grumble that blight has cut profits, in impoverished Russia potatoes are the next meal. In the Indian state of Andhra Pradesh, where a rampant bollworm infestation adds to the already crushing debt of small farmers, 10,000 desperate peasants have committed suicide in the past decade. Geoffrey Hawtin, head of Global Conservation Trust, a Rome-based research agency, puts it starkly. “For the little guy, a failed crop means you starve,” he says.
Producers large and small have generally –shrugged off the fight against bugs and bacteria as part of the trade-off for a brimming silo. No longer. Rice yields have been stagnant in Asia for more than a decade. With water growing scarcer, irrigation has actually retreated, down 10 percent per capita in the past 25 years. As the green revolution loses momentum, pressure on farmers to compensate with ever-bigger harvests will be even greater. Says David Pimentel, an agricultural ecologist at Cornell, “We are bumping up against the limits of the model.” Demographers expect that not only will the world’s population swell to 9 billion by 2050, demand for food will surge nearly 2i-fold, driven by rising incomes.
To wrest more food from the earth, producers will either have to pump more yield out of the same tired plots–blitzing the soil with fertilizers and pesticides–or push cultivation onto weaker soils and chop down forests. Each harvest will bring more erosion, pollution, salinization of water and water logging of the soils. “We are on a trajectory that is not sustainable in the long run,” says Tilman.
In China now, plants bred for disease resistance last five years before the germs catch up. Tilman reports that maize hybrids in the United States typically remain disease-free for four years–half the shelf life of 30 years ago. Bugs can beat the best insecticides in a decade. Spraying fungicides and pesticides now accounts for a quarter of all costs for banana growers. Fertilizers are double agents: “We’re feeding plants and making them more nutritious, and the pests like that, too,” says Pimentel. The world, he says, loses 40 percent of potential food production a year despite the use of 2.7 billion kilograms of pesticide.
The banana may be the worst casualty of the modern plantation system. Some 500 million Asians, Africans and Latin Americans depend on it for calories and income, yet few crops are as cursed. Emile Frison, head of the International Plant Genetic Resources Institute in France, estimates that 40 percent to 50 percent of the world banana harvest is lost to insects and diseases. Ten millennia ago, the banana was a big, starchy thing stuffed with seeds as hard as stones. But early farmers carefully culled and cultivated the rare edible fruits and, over time, begat an elegant golden crescent with a filet of sweet, smooth flesh. Of 500 varieties, the only banana people in rich countries ever see is the Cavendish, a huge cash crop.
The problem is, the perfect Cavendish banana is perfectly sterile. Centuries of careful breeding have shrunk the once virile pits to a sexless streak of black dots (farmers breed it by cloning). In the wild, sexual reproduction equips a plant with a mixed bag of genes that get jumbled again and again with each generation–making it a moving target for disease. The chaste Cavendish is a pushover. Black sigatoca, a once rare fungus, is now an epidemic. Cavendish growers spray their crop with fungicides up to 50 times a year, at a cost that experts say may price this banana out of the market.
It’s not only wonder foods that are threatened. Malaysian customs inspectors pore over baggage as though they were looking for weapons-grade plutonium. What worries them is microcyclus ulei, the rubber-tree leaf blight. Together, Malaysia and its Southeast Asian neighbors produce 92 percent of the world’s natural latex, which synthetic rubber has never equaled for elasticity and heat resistance. So far leaf blight has not spread beyond the West Indies and Central and South America. But the Asians are taking no chances. To this day travelers from Brazil, where the blight is endemic, may not set foot on Malaysian soil without first spending several days in quarantine in Europe. There is even a blight brigade on call, ready to defoliate an entire plantation at the first hint of infection. If the leaf disease ever makes the jump to tropical Asia–scientists have little doubt it will eventually–“the world rubber supply would collapse,” says Eurico Pinheiro, a Brazilian rubber expert.
The task for scientists is to find a way of producing food efficiently while keeping the planet healthy at the same time. Genetic engineering may help boost immunity in sterile plants (the banana) or those in which virtually all varieties (potatoes, papaya) are vulnerable. Brazilian agronomist Manoel Texeira engineered papayas to withstand ringspot virus, which causes $35 million in damages a year. But Brazil has outlawed transgenic crops. “It’s extremely frustrating,” Texeira says.
Another way out may be to take a gamble on diversity. Thirty years ago, at the height of the green revolution, a few prudent policymakers and geneticists scoured villages and forests for varieties of plants that had been left behind. Some 6 million samples are on ice in more than 1,000 gene banks worldwide. Zhu believes that after millennia of discarding crops, farmers can use these lost seeds to resurrect variety in their fields. When he urged peasants in Yunnan to plant two different strains of rice, thus imitating nature’s genetic firewall to disease, losses to blight and blast dropped significantly.
Experiments like Zhu’s offer a way out of the monoculture trap, but will they catch on? History is not encouraging. Only a few wild plants–strawberries, blueberries, pecans–have been added to the human diet in hundreds of years. “Everyone knows that to grow more food we need to go back to the well of diversity,” says Tilman. “We need to be looking at agriculture not in the near future but over the next 10,000 years.” That kind of perspective usually comes only in a crisis.
