Dr. James E. McWilliams is the author of “Just Food: Where Locavores Get It Wrong and How We Can Truly Eat Responsibly.” The following quotes are from an op-ed piece he published in The New York Times on 2012 April 12.

For all the strengths of these alternatives, however, they’re ultimately a poor substitute for industrial production. Although these smaller systems appear to be environmentally sustainable, considerable evidence suggests otherwise.

Grass-grazing cows emit considerably more methane than grain-fed cows. Pastured organic chickens have a 20 percent greater impact on global warming. It requires 2 to 20 acres to raise a cow on grass. If we raised all the cows in the United States on grass (all 100 million of them), cattle would require (using the figure of 10 acres per cow) almost half the country’s land (and this figure excludes space needed for pastured chicken and pigs). A tract of land just larger than France has been carved out of the Brazilian rain forest and turned over to grazing cattle. Nothing about this is sustainable.

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The economics of alternative animal systems are similarly problematic. Subsidies notwithstanding, the unfortunate reality of commodifying animals is that confinement pays. If the production of meat and dairy was somehow decentralized into small free-range operations, common economic sense suggests that it wouldn’t last.

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