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Chapter 9. Feeding Eight Billion Well: Moving Down the Food Chain
One of the questions I am most 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 a population of 10 billion. 60
In every society where incomes rise, people move up the food chain, eating more animal protein as beef, pork, poultry, milk, eggs, and seafood. The mix of animal products varies with geography and culture, but the shift to more livestock products as purchasing power increases appears to be universal.
As consumption of livestock products, poultry, and farmed fish rises, grain use per person also rises. Of the roughly 800 kilograms of grain consumed per person each year in the United States, about 100 kilograms is eaten directly as bread, pasta, and breakfast cereals, while the bulk of the grain is consumed indirectly in the form of livestock and poultry products. By contrast, in India, where people consume just under 200 kilograms of grain per year, or roughly a pound per day, nearly all grain is eaten directly to satisfy basic food energy needs. Little is available for conversion into livestock products. 61
Of the three countries just cited, life expectancy is highest in Italy even though U.S. medical expenditures per person are much higher. People who live very low or very high on the food chain do not live as long as those in an intermediate position. Those consuming a Mediterranean type diet that includes meat, cheese, and seafood, but all in moderation, are healthier and live longer. People living high on the food chain, such as Americans or Canadians, can improve their health by moving down the food chain. For those who live in low-income countries like India, where a starchy staple such as rice can supply 60 percent or more of total caloric intake, eating more protein-rich foods can improve health and raise life expectancy. 62
In agriculture we often look at how climate affects the food supply but not at how what we eat affects climate. While we understand rather well the link between climate change and the fuel efficiency of the cars we buy, we do not have a comparable understanding of the climate effect of various dietary options. Gidon Eshel and Pamela A. Martin of the University of Chicago have addressed this issue. They begin by noting that the energy used in the food economy to provide the typical American diet and that used for personal transportation are roughly the same. In fact, the range between the more and less carbon-intensive transportation options and dietary options is each about 4 to 1. With cars, the Toyota Prius, a gas-electric hybrid, uses scarcely one fourth as much fuel as a Chevrolet Suburban SUV. Similarly with diets, a plant-based diet requires roughly one fourth as much energy as a diet rich in red meat. Shifting from a diet rich in red meat to a plant-based diet cuts greenhouse gas emissions as much as shifting from a Suburban SUV to a Prius. 63
The inclusion of soybean meal in feed rations to convert grain into animal protein more efficiently, the shift by consumers to more grain-efficient forms of animal protein, and the movement of consumers down the food chain all can help reduce the demand for land, water, and fertilizer. This reduces carbon emissions and thus helps to stabilize climate as well.
60. Author’s calculations from USDA, op. cit. note 1; U.N. Population Division, op. cit. note 5.
61. USDA, op. cit. note 1; U.N. Population Division, op. cit. note 5; FAO, op. cit. note 34.
62. Organisation for Economic Co-operation and Development, “Total Expenditure on Health Per Capita, US$ PPP,” table, OECD Health Data 2007-Frequently Requested Data, at www.oecd.org, July 2007; FAO, op. cit. note 34.
63. Gidon Eshel and Pamela A. Martin, “Diet, Energy, and Global Warming,” Earth Interactions, vol. 10, no. 9 (April 2006), pp. 1–17; USDA, op. cit. note 1; U.N. Population Division, op. cit. note 5.
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