High-yield crops

High-yield crops are cereal varieties — chiefly wheat and rice — bred deliberately to make the most of fertilizer and water. The key trait is short stature. Traditional cereals are tall; feed them heavy nitrogen and they grow taller still, then fall over (lodge) under the weight of a big grain head, rotting on the wet ground. Green Revolution varieties carry dwarfing genes that keep the stalk short and stiff, so the plant puts the extra nutrition into grain it can actually hold up. Norman Borlaug's semi-dwarf wheats, developed in Mexico from the 1940s onward and carrying a dwarfing gene from the Japanese variety Norin 10, were the breakthrough; the parallel rice line, IR8 or "miracle rice," was released by the International Rice Research Institute in 1966.

By the mid-twentieth century, population was outrunning food in much of Asia, and forecasts of mass famine in India and Pakistan were mainstream. High-yield varieties, planted with fertilizer and irrigation, broke the trend: Mexican wheat output climbed several-fold, and India and Pakistan roughly doubled their wheat harvests in a handful of years, pulling back from the brink. The scale of the reprieve is why Borlaug is credited with saving on the order of a billion lives and why the effort as a whole is called the Green Revolution.

Food output that kept pace with, and for decades outran, population growth across much of the developing world, averting predicted famines and reshaping the demographics of Asia. It also bound farming tightly to industrial inputs — fertilizer, irrigation, and later pesticides — with real costs in water depletion, soil and runoff problems, and the narrowing of crop diversity as thousands of local landraces gave way to a few elite lines. The Green Revolution is both one of the clearest humanitarian successes of modern science and the origin of the sustainability debates that define agriculture now.