What's in a Number?
How the press got the idea that food travels 1,500 miles from farm to plate.
Food critics may be finicky when it comes to celebrity chefs, but their affection for local ingredients never flags. It's hard to open a magazine without finding an article about a photogenic farmer making handcrafted cheese or a happy family that has reduced its carbon footprint by planting a victory garden. And it seems like nearly every one of these stories offers up the same disheartening statistic to wean Americans off their penchant for industrially farmed suppers: On average, food travels 1,500 miles from farm to plate.
Back in May, chef Dan Barber noted on the New York Times op-ed page that $4 per gallon diesel fuel means "it's no longer efficient to transport food 1,500 miles from where it's grown." When Wal-Mart decided to start buying more local produce last July, the company issued a press release stating that an average meal travels 1,500 miles "before it gets to you." The stat has popped up in Newsweek, Time, even Slate's own 2006 "Green Challenge." Not since Newsweek announced that a woman had a better chance of getting killed by a terrorist than getting married after 40 has a statistic been embraced so enthusiastically.
There's just one problem. It's only sort of true—and only if you live in Chicago.
The statistic was first published in 2001 when Rich Pirog, associate director of Iowa State University's Leopold Center for Sustainable Agriculture, wanted to figure out which food distribution system—local, regional, or national—is the most environmentally friendly. To do so, he and a team of researchers looked at food miles, long a common measure in Europe. By calculating how far food traveled, they could determine the corresponding amount of carbon dioxide released into the air.
For the report, researchers examined how far 33 fruits and vegetables that had been grown in the United States traveled to a produce market in Chicago. The data, collected by the Department of Agriculture, aren't ideal; over the last 30 years, terminal markets have declined in importance, in part because retailers like Wal-Mart manage their own distribution. In 1998, the last year data were collected, the country's 22 terminal markets handled only 30 percent of the nation's produce. But the data are public and therefore free to academics.
In addition to being a limited sample, terminal market data indicate only the state where the produce was grown, not what part of the state. So, for example, Pirog could have known oranges came from Florida but had no way of discerning whether they came from around Palm Beach or Orlando. For practical purposes, his team assumed that all produce came from the geographical center of each state. They then used MapQuest to determine the route a truck might take to the Chicago market. That's a decent approximation for a high-production state like California, where crops are grown from north to south. But it's flat-out wrong for Oklahoma, whose capital city is smack dab in the center of the state.
Jane Black, formerly a food writer at the Washington Post, is currently at work on a book about food culture and class in Huntington, W.Va. She blogs at www.janeblack.net.
Illustration by Mark Alan Stamaty.