Conventional wisdom says that we should seek out food that is seasonal, minimally processed, and produced within our local foodshed. (The 100-Mile Dieters, or locavores, take this as close to its logical extreme as you can get without raising all your food in your own backyard.) The reasons to keep it local are intuitive and many: buying local supports nearby farmers, increases the visibility of local farms, improves the local economy, promotes urban agriculture, preserves rural farmland and prevents sprawl, and minimizes the air pollution and greenhouse gas emissions created when transporting our food from farm to table.
Another reason is that local food just tastes better. :ong-transported food can deteriorate on the way to becoming dinner, and so is often bred to be hardy enough to survive trips of many miles at the expense of tastiness . The average head of broccoli travels 2,095 miles from farm to table; the average apple, 1,555 miles. The boom in the number of miles industrial produce travels, along with the widespread desire to have more of a positive impact on local communities and less of a negative one on the environment, has led some advocates to suggest that all food be labeled with "food mile" information, indicating how far it has traveled to market.
A much-covered recent study, however, gave some local-food advocates pause by suggesting that when it comes to carbon emissions, buying local may not be the panacea it appears to be. Researchers at Lincoln University in New Zealand looked at the environmental impact of various foods through a "life cycle analysis" matrix that factored in external factors such as water use, harvesting techniques, the use of renewable energy sources, the means of transport, and storage procedures, among other factors. We've written about their findings before, but here’s the basic claim: Imported food can, in some cases, actually have less impact on the atmosphere than food grown locally and transported to local supermarkets, if all these other factors besides miles traveled are taken into account. The prime example is New Zealand lamb: when shipped to England, it produced a mere quarter of the carbon emissions produced by lamb raised in England's nutrient-poorer pastures. The study reached similar conclusions about New Zealand's apples and dairy foods.
But wait -- it isn't that simple. As critics of life cycle analysis have pointed out, its supporters base their praise on studies of industrial farming methods. (One notable proponent of life cycle analysis is James McWilliams, whose recent New York Times op-ed singing its praises has revived the controversy.) Comparing lamb raised organically on a small pasture to one raised on a factory farm, albeit locally, is hardly apples to apples. Moreover, the study did not include several important factors in carbon production, including the carbon cost of trucking meat and produce from place to place. And the study assumed that fuel and fertilizer would continue to be inexpensive and widely available -- not the safest assumption in a world increasingly impacted by climate change.
What does all of this mean for those of us who want our food to have a minimal impact on the climate? For one thing, it means that we can't rely on simple conclusions from single studies. Yes, there’s more to the carbon impact of food than whether it’s local or not, but in many cases local and organic food may still be the best choice.
It also reveals the need for a single labeling system that goes beyond whether a food is organic and point-of-origin labels to include information such as where the food was produced; whether it's in season; whether it was chemically treated and if so, how; how much water was used to produce it; and whether it was grown by a small farm or massive agricultural corporation.
Carbon labeling shows tremendous promise in unifying all these confusing considerations into a single, easy-to-digest standard. If done right, carbon labeling would go a long way toward eliminating all the sticky decisions and tradeoffs environmentally conscious consumers must now make. But true carbon labeling is still years in the future. In the meantime, the best we can do is measure what we know, decide which factors are most important, and -- most importantly -- buy from stores, and farmers, we know and trust.
