Local food enthusiasts have been trying to make the case that buying food from farmers nearby supports local economies, boosts food security and is better for the environment.
But so far, "local" food still makes up a pretty small fraction of what Americans eat. And given that most agriculture in the U.S. is geared toward producing food crops — from corn to soybeans to almonds — for the global market, it doesn't seem likely that will change.
But according to a recent study by researchers at the University of California, Merced, it's actually possible to grow a lot more food closer to our cities.
"If you drew a 100-mile circle around each city in the U.S. and then you looked at the capacity of the existing farmland, you'd find that 90 percent of the people could be fed within those circles," says Elliott Campbell, an associate professor of environmental engineering at U.C. Merced who co-authored the study.
Over the last two years, Campbell has been exploring the idea of "foodshed potential," or "the fraction of total dietary needs that could be met if all existing croplands were repurposed for local food consumption," as he and his co-author Andrew Zumkehr write in the paper.
And while the potential was highest looking at a 100-mile radius around cities, they also found that most areas in the U.S. could supply 80 to 100 percent of their populations with fare grown or raised within 50 miles.
"Very few farms in the U.S. are currently used for local food and instead are contributing to very long supply chains," Campbell tells The Salt. "If we wanted to earmark some of our croplands for our local needs it would be absolutely no problem to be 100 percent self-sufficient [in many places]."
For example, in rich farming regions like California's San Joaquin Valley, they estimate that the city of Fresno could feed all its residents year-round with local food. Other cities would have more trouble: Campbell and Zumkehr found that New York City could only provide 5 percent of its residents with completely local food within a 50-mile radius, but could get to nearly 30 percent within 100 miles.
So why isn't this already happening? Campbell says many farms are serving markets far beyond their local cities. Also, he says, much of the food people currently eat is processed and packaged — rather than locally grown fruits and vegetables.
Yet shifting to a more local foodshed system — while challenging — could yield benefits in nutrition and health.
"There's some evidence that these local food systems, farmers markets, can get people to consume more fruits and vegetables," Campbell says. "It's a really tough thing to get people to shift their diets, and if there's some potential for local food to do that I think it's well worth further looking into."
Not everyone is buying Campbell's conclusions. Steven Sexton with the Sanford School of Public Policy at Duke University has long been a critic of local food — in this 2011 Freakonomics post, he wrote that the assumption that a "relocalized" food system would be better is wrong.
As for Campbell's study, Sexton is skeptical about the measurements.
"They're estimating how many calories silage and hay can be produced within a given radius of the cities," Sexton says. "That's fine if Americans are just consuming calories, but Americans consume food products."
Measuring tools aside, Sexton still doesn't think Campbell's theory is foolproof. First, American's aren't used to eating seasonally — we want strawberries in winter and oranges in summer — and are accustomed to huge variety year-round.
"People who live in certain parts of the country could eat local and have a balanced diet, like California," Sexton says. "What this means for a lot of other parts of the country like the Midwest and the Northeast for substantial portions of the year if they are going to be eating any vegetables they are going to be pickled canned or frozen."
Second, he says a switch to consuming only local food would increase prices.
"This is not a way to encourage consumption of healthy foods, and it's likely going to occur at some higher cost," Sexton says.
But even still Campbell says by creating models and maps his main purpose is to show how much potential there is to still eat local in America.
"If this idea became a reality there's going to be a number of obstacles from a social point of view of what people's preferences are, from an economic point of view where there's infrastructure and support for local food," Campbell says. "But the maps we've provided give you a sense of where it would make sense to allocate resources to ramp this up."
As for which city should try it first? He says he'll leave that up to politicians.