After several decades of rapid rise in world grain yields, it is now becoming more difficult to raise land productivity fast enough to keep up with the demands of a growing, increasingly affluent, population. From 1950 to 1990, world grainland productivity increased by 2.2 percent per year, but from 1990 until 2009 it went up by only 1.3 percent annually. Despite some impressive local advances, the global loss of momentum in expanding food production is forcing us to think more seriously about reducing demand by stabilizing population, moving down the food chain, and reducing the use of grain to fuel cars.

One of the key components of Plan B, the Earth Policy Institute’s ambitious strategy to save civilization, is to halt world population growth at no more than 8 billion by 2040. This will require an all-out population education effort to help people everywhere understand how fast the relationship between us and our natural support systems is deteriorating. It also means that we need a crash program to get reproductive health care and birth control services to the more than 200 million women today who want to plan their families but lack access to the means to do so.

While the effect of population growth on the demand for grain is rather clear, that of rising affluence is much less so. One of the questions I am often asked is, “How many people can the earth support?” I answer with another question: “At what level of food consumption?” Using round numbers, at the U.S. level of 800 kilograms of grain per person annually for food and feed, the 2-billion-ton annual world harvest of grain would support 2.5 billion people. At the Italian level of consumption of close to 400 kilograms, the current harvest would support 5 billion people. At the 200 kilograms of grain consumed by the average Indian, it would support 10 billion.