Tom Philpott breaks down another argument for Factory Food and Big Agriculture. He is fast becoming a favorite food writer and journalist.

First of all, it’s important to understand what the researchers did. They rounded up all the rigorously documented studies, both domestic and global, they could find that compared organic yields and conventional yields (66 studies met their criteria) and averaged them out. The only focus was gross output per acre—no consideration of, say, ecological trouble like the plight of honeybees and other pollinators in a sea of pesticide-laced crops, or resources consumed, like synthetic nitrogen fertilizer, which is made with natural gas. So, despite what Walsh wrote, the study didn’t really tell us much about the relative efficiency of the systems beyond output per chunk of land. Viewed through the study’s yield-per-acre lens, industrial agriculture looks hyperefficient, and organic like a laggard.

And indeed, big farms in Iowa—the example Time's Walsh pointed to—do produce mountains of corn per acre. But dig a little deeper, and the picture muddies. The authors note that conventional ag produces high yields through abundant use of synthetic nitrogen fertilizer. But they don't account for the fact that nitrogen runoff from farms generate also contributes to amassive annual dead zone that snuffs out a swath of what should be a highly productive fishery in the Gulf of Mexico. Such externalities, as economists call them, are not accounted for in the study.