Tim Harford steps up to bat in the debate about the damage done by food miles, the distance and environmental cost of shipping food worldwide, with some new data from British economists, who find that:
flying fresh food around the planet carries an environmental cost of no more than a few cents per meal. That sounds astonishing, but perhaps it shouldn't be. Those Chilean grapes aren't flying first class: They're packed tight to save money, which incidentally saves on pollution.
locally grown food has its own environmental costs. Academics from New Zealand have produced evidence that it is environmentally friendly to produce dairy products, apples and lamb in New Zealand–where there is plenty of space to accommodate natural, energy-efficient methods of farming–and ship them around the world. Maybe the New Zealanders would say that, but it's not a crazy observation. Eating local can consume fossil fuels too: [Local food advocate Bill] McKibben enjoyed berries in the winter because he froze them for months. Local tomatoes are grown in northern climes in gas-heated greenhouses. And local doesn't necessarily mean "natural": local apples can be stored for months–in storage sheds filled with nitrogen.
If you're really worried about how to reduce the social costs of your diet, consider this: "Two-thirds of the social costs of the food distribution system have nothing directly to do with the environment at all: They are attributable to accidents and congestion." So your picturesque drive into the city center to hit the farmer's market, or out to the country for leaf peeping and apple picking are imposing more social costs than my Chilean grapes. By extension, walking to the big "industrial" supermarket in your neighborhood may be most responsible food choice you can make.