Reservoirs gone dry, crops shriveled in fields, ever-higher food prices looming. The historic drought choking California is a window into a future of global over-population and other environmental pressures that could cause mass starvation, epidemics and war, according to Paul Ehrlich, the Bing Professor of Population Studies and a senior fellow at the Stanford Woods Institute for the Environment.

“There’s a failure to understand this is what’s expected with climate change and run-away population growth,” Ehrlich said.

At this year’s American Association for the Advancement of Science (AAAS) Annual Meeting in Chicago, Ehrlich discussed “Feeding 9 Billion and Avoiding a Collapse of Civilization: Science's Main Challenge,” as part of a symposium called “Feeding a Growing Population While Sustaining the Earth.” In the talk, based on a 2013 paper he co-authored, Ehrlich outlined a range of threats facing world food supplies and suggested possible solutions.

“Humanity is taking a gigantic gamble in assuming it can feed more than 9.7 billion people in 2050, a third more than exist today, without revolutionary changes in behavior,” Ehrlich said. Among the challenges Ehrlich noted in his AAAS talk:

• climate disruption’s effect on irrigation water and crop yields
• ocean acidification’s effect on fisheries
• the modern food system’s oil dependence and its global warming gas emissions (“Twenty-five to thirty-five percent of emissions come from agriculture, but we don’t hear that.”)
• pesticide and fertilizer contamination of freshwater and oceans
• loss of pest-control services provided by predators and winter weather
• the loss of natural crop pollinators such as bees
• population pressures (“It would be a hell of a lot easier to feed 8.2 billion people.”)
• pressures on grain production due to a growing demand for meat
• the need for sufficient employment to ensure people can afford to purchase food (“If we remain in the system we have today, there are going to be a lot of people starving because they don’t have the money to buy food.”)

Although betting that we can resolve these challenges is a long-shot, Ehrlich said, there is cause for hope. In addition to approaching demographic shrinkage in many developed nations, there is “great room” for improving grain yields in Africa, building rural health clinics and providing access to contraception and backup abortion, Ehrlich said.

The odds of avoiding a collapse could be improved, according to Ehrlich, if society takes a range of bold steps, including:

• coordinated efforts to stop the expansion of agricultural land and preserve ecosystem services
• more efficient use of water, energy and fertilizer
• less meat consumption and more education about balanced diets that include minimal meat
• a shift toward “middle-size” agricultural operations that can take advantage of economies of scale while practicing more responsible land husbandry (“The big trend in agriculture has been industrialization and to grow food for money, not to feed people.”)
• better agricultural research and development (“Plant geneticists are going to be at the front lines.”)

Ehrlich emphasized the need to empower women with equal rights, shift economic priorities to value natural capital and better educate all people about agriculture. “Since most people have no idea where their food comes from, they’re not concerned with the agricultural system.”

Ehrlich acknowledged the uphill battle for his prescriptions, but pointed out that consumption patterns can change “overnight” as they did during World War II to support the industrial war effort. To learn more, we need more focus on human behavior, Ehrlich added. “I’m absolutely convinced the problem is in the hands of social scientists.”