Food security: What crops will feed the world if we run out of farmland?

In The Future, Will We All Be Forced To Eat Yams?

In The Future, Will We All Be Forced To Eat Yams?

The citizen’s guide to the future.
June 12 2012 6:30 AM

I Think, Therefore I Yam

When farmland is scarce, will we all eat roots and tubers?

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A world of yam-eaters might seem far-fetched, but some food-security zealots are already preparing for the worst. One of them is John Jeavons, a Willits, Calif.-based advocate of what he calls “biointensive farming.” Back in the early 1970s, when people still feared the original population bomb, Jeavons began to explore how people could grow everything they needed on the smallest possible plot of ground. Building on the methods of organic-farming pioneer Alan Chadwick, Jeavons developed an eight-point gardening system that calls for close spacing of plants, vigorous composting and soil maintenance, and “calorie farming,” which means focusing on crops that produce the most nutrition in the least space.

According to the FAO, sweet potatoes top the list, yielding 70,000 calories per hectare per day, nearly twice as much as wheat—and far more than that if you use one of several fast-maturing varieties. Jeavons also recommends potatoes, leeks, and parsnips for those looking to maximize calories per acre. (Cassava, a crucial subsistence crop in many developing countries, is less efficient because it takes longer to grow.) In the ideal subsistence farm, Jeavons says, roots and tubers would account for 30 percent of all the land cultivated for food.

His techniques, spread through his nonprofit Ecology Action, have caught on with some farmers in countries like Kenya, where farmland is scarce and people are hungry. The question is, could that movement catch on globally?


Jeavons is optimistic that farmers, consumers, and world policy-makers will come around if and when the world’s impending food crisis becomes more apparent. But much of the world’s food is produced under contract with multinational processing and distribution companies whose interest is in maximizing profits, not calories. Factory farms tend to focus on one or two crops, a strategy that might damage the land over time but is highly efficient in the short term. Suggest to an agribusiness executive that he start devoting half his land to the cultivation of compost and another big chunk to salsify and Jerusalem artichoke, and he’ll probably laugh.

On the consumption side, new-wave nutrition gurus such as Michael Pollan have sold a lot of books calling for Americans to eat less fast food and more organic vegetables, and the nation’s meat consumption appears to have peaked around 2007. But organic farming actually yields less food per acre than today’s conventional methods, at least in the short term. And compared with fresh veggies, roots and tubers are probably a tougher sell for your average Whole Foods shopper. Even a spike in food prices might not be enough to make most Westerners change their diets substantially. “Things would have to get really bad to make people eat less meat and more cassava,” Zilberman says. (He thinks genetic engineering is a more realistic solution.)

Instead, it would hurt the people in poor countries who have trouble affording food as it is. In a world where there isn’t enough food to go around, one thing probably won’t change: Most starvation will still be a product of inequality rather than global supply shortage. It’s just that there will be a lot more of it there is now.

Also in the special issue on food: five “food frontiers,” including technologies to make diet food tastier and fight salmonella; smart packaging may help keep your produce from going bad; small-scale farmers decide whether to embrace automated agricultural equipment; and the case for bringing back home ec. This article arises from Future Tense, a joint partnership of Slate, the New America Foundation, and Arizona State University.