Betting on the population bomb

When an economist from the University of Michigan named David Lam addressed the 2011 annual meeting of the Population Association of America, he sounded an upbeat note about our ever more populous planet. "I am sure that by the time of the 2050 PAA annual meeting, the world will still face important challenges," he said. "But I also expect that it will have improved in many ways, including lower poverty rates, higher levels of education, and plenty of food to go around." Lam alluded to a famous occasion when the optimistic economist Julian Simon bet the pessimistic biologist Paul Ehrlich that global mineral prices would decline over a 10-year period despite rising population and demand. Ehrlich lost that bet, and Lam said that were anyone to make a similar bet against his predictions, he thought they'd lose, too.

Stanley Becker of the Bloomberg School of Public Health was in the audience for Lam's address. Becker is a professor of population, family, and reproductive health, and he decided to take up Lam's challenge. So at a gathering last October at Johns Hopkins to mark the global human population reaching 7 billion, Becker and Lam announced a wager. Lam bet that the inflation-adjusted prices of five foods—cereals, dairy, meat, oils and fats, and sugar—will decline from 2011 to 2020, and Becker bet that they will go up. The two professors agreed that the loser will donate up to $1,000 to a nongovernmental organization of the winner's choosing.

In "How the World Survived the Population Bomb: Lessons From 50 Years of Extraordinary Demographic History," published in Demography, Lam notes that despite a doubling of global population from 1960 to 1999, food supplies per capita substantially increased while prices declined. "There were many concerns about the potential impact of rapid population growth in the 1960s, including mass starvation in countries such as India, depletion of nonrenewable resources, and increased poverty in low-income countries," he wrote. "The actual experience was very different. World food production increased faster than world population in every decade since the 1960s, resource prices fell during most of the period, and poverty declined significantly in much of the developing world." He felt confident that through hard work and creativity, those trends would sustain despite continued rapid population increases.

"He's saying basically that things are looking good, and since they've been relatively good over the last 50 years, he thinks the future isn't that bad," Becker says. As a social demographer with an ecological orientation, Becker has considered a variety of factors and come to a more pessimistic conclusion. As about 75 to 80 million additional people join the world's population each year, global aquifers are being tapped for water at a rate that exceeds their rate of replenishment. That's water vital for farm irrigation, among other uses. Becker points out that most of the globe's arable land is already under cultivation, with no guarantee of everincreasing yields. Furthermore, global climate change could disrupt agricultural production in important areas like the American Midwest (Becker notes that this is already happening due to drought). "There's lots of land in the Congo and Brazil under rain forest, but you chop that forest down and find the land is not that good for farming," he says. In rapidly developing countries like China, newly prosperous people are eating more meat, and meat production is a far less efficient use of agricultural resources than production of vegetable protein. Much agricultural production is dependent on oil in various ways, and oil supplies are finite. Fish stocks in the world's oceans have declined to the point that vast areas of the sea are fished out of some species. All of which feeds Becker's doubts about stable food prices.

"There could be a breakthrough," Becker says. "I could be wrong for a bunch of reasons. There are likely to be food subsidies by governments to prevent food riots. Maybe we'll have another Green Revolution, a green Green Revolution. I ask my classes, how many of you are vegetarian? A few hands go up. So if we were all vegetarians, we could probably feed 10 billion people. How many would eat seaweed? Fewer people raise their hands. If we all ate seaweed, we could probably feed 12 billion because there's a lot of seaweed out there. You know how things change, so who knows?"