The question of whether to buy locally grown food is not as clear as it might appear.
When shopping for food, how important is it to buy local? This question isn’t rhetorical: I no longer know quite what to think about this. Obviously, transporting food long distances requires fossil fuels and creates air pollution, among other ills. So all else being equal, it’s better to buy local. But how much better, I’m just not sure.
Studies such as this one (reported on here by the BBC, blogged about here) suggest that, in terms of net environmental impact, it’s even more important to buy local than to buy organic. The authors of the study didn’t look at human health issues, but did attempt to quantify all sorts of environmental "externalities" — i.e., costs not borne by the consumer — resulting from food production. And they found that transportating food was far and away the largest component of external environmental costs. In other words, the closer to home the food is grown, the better it is for the planet.
But then there’s this analysis, from the Earth Policy Institute:
The U.S. food system uses over 10 quadrillion Btu (10,551 quadrillion Joules) of energy each year … 21 percent of overall food system energy is used in agricultural production, another 14 percent goes to food transport, 16 percent to processing, 7 percent to packaging, 4 percent to food retailing, 7 percent to restaurants and caterers, and 32 percent to home refrigeration and preparation.
Wading through all these numbers, it looks as though food transport is not as big a deal as I’d thought. According to the US Energy Information Administration, the US consumes about 100 quadrillion BTUs (or "quads") of energy each year. If the Earth Policy Institute is correct, then transporting farm products takes about 14% of 10 quads, or about 1.4 quads a year. That’s a huge amount of energy, admittedly, so buying local certainly helps. But still, transport is only the fourth largest component of the food system — which means that, as a consumer, you can probably squeeze out just as much energy savings by getting a more efficient refrigerator or stove, or eating more grains and veggies and less meat, as by buying local.
And then there’s this, from p. 62 of the Union of Concerned Scientist’s venerable Consumer’s Guide to Effective Enviornmental Choices:
Transportation accounts for 26 percent of ghg emissions from the fruit, vegetable, and grain category, but only 0.6 percent of all emissions traceable to consumer purchases.
Now, if this is right, then moving food all around the country (as eco-unfriendly as the practice may seem on its face) is a relative drop in the bucket. Or, er, oil barrel. According to the book, personal transportation and household operations — mostly, what and how far you drive, and how you heat and power your house — account for more than two-thirds of an individual’s GHG emissions. That’s about 100 times as much energy as is used transporting fruits, vegetables and grains. So by this reckoning, growing all of your food in your own backyard isn’t as important as improving your car’s gas mileage by a mere 3 percent. Or, put differently, all else being equal, it may be wiser to choose a home within walking distance of a grocery store than one that’s adjacent to the fields where your food is grown.
Obviously, there’s a lot to consider here. First of all, the numbers feel, well, squishy to me. When I was researching this post, I found all sorts of estimates of how much energy goes into agriculture; the sources I highlight in this post seem credible and well-reasoned, but I don’t think they’re in any sense definitive. Second, one shouldn’t just consider the global-warming implications when making consumer choices. There are all sorts of good reasons — practical and emotional, environmental and economic — to buy locally grown food. But since my time, money, and attention are all limited, I like to concentrate my efforts on the choices that make the biggest difference. The problem is that now I’m just not sure how big an environmental priority to assign to buying local food: Is it the most important choice you can make, or a relatively minor one? What was once clear is now, to me, opaque.
And finally: High oil prices have spawned renewed concern over fuel shortages in the coming decades — and since modern agriculture certainly requires lots of fuel, some folks seem especially worried whether there will be enough food to go around. That’s a reasonable enough thing to worry about. But again and again I hear people argue that the best solution is to go "back to the land" — to spread out over the landscape, and carve up corporate mega-farms into small homesteads so that the food doesn’t have far to go from farm field to table. That could work, I suppose. But that sort of ultra-low-density sprawl runs exactly counter to the examples of the world’s most energy-efficient economies, in which people tend to concentrate in compact urban areas where they don’t have to drive much to get around.
Which suggests that how much I drive is likely of far greater consequence than how much my food does.