In the late eighteenth century, the English political economist Thomas Malthus took a look at two sets of numbers and had an unnerving vision: with food supplies increasing arithmetically while the number of people grew geometrically, the world population would eventually run out of food. "By that law of our nature which makes food necessary to the life of man," he wrote in 1798, "the effects of these two unequal powers must be kept equal. This implies a strong and constantly operating check on population from the difficulty of subsistence. This difficulty must fall some where and must necessarily be severely felt by a large portion of mankind."
He was right, at least at the time: in Malthus' day, food production was essentially limited by the availability of land, whereas procreation faced few restraints. Malthus did not foresee, however, that new technologies in the late nineteenth century and throughout the twentieth century would dramatically raise agricultural productivity. Farmers worldwide learned to use new fertilizers, petrochemical-based herbicides and insecticides, genetically improved plants (especially wheat, corn, and rice), and massive diversions of water for irrigation, notably in China and South Asia. Crop yields soared, and in the United States so much so that by the 1950s chronic surpluses and low prices were becoming problems. The economist Willard Cochrane wrote in 1965 that thanks to the recent technological revolution in U.S. agriculture, the previous decade had witnessed "the greatest gain in productive efficiency of any ten-year period in the history of American farming."
Throughout the 1960s, 1970s, and 1980s, crop yields continued to rise, not only in rich countries but also in many parts of the developing world. In India, Mexico, and elsewhere the "green revolution" was launched by plant breeders, such as the legendary Norman Borlaug. New varieties of wheat, maize, and rice raised yields by amounts that seemed miraculous at the time. The effort provided a new model for traditional farmers and improved their food security. And it encouraged a sense of purpose