This was quite interesting and rather counterintuitive. I quote:
Local is the new organic. If you believe the hype, every environmentally minded, socially conscientious shopper should be buying food from local farms. We are meant to fret about the vast distances traveled in airplanes by Kenyan beans or Chilean grapes. The movement uses the censorious label “food miles,” designed to echo “air miles.”
Those Chilean grapes aren’t flying first class: They’re packed tight to save money, which incidentally saves on pollution. The most wasteful part of the journey is when you and I hop in our cars and drive to the shops and back with a bag of potato chips in the trunk of the car.
The local food movement would argue that local food is about more than just the environmental cost of transportation. Fair enough. But the connection between local food and some of its supposed benefits is pretty tenuous. If it's fresher food, cheery farmer's markets and decent conditions for farm workers that we want, let’s address those aims directly without this fetish for localism.
There’s a twist in the tale, too. 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. More than half of those costs are caused by driving to the shops. My socially responsible advice to you, then, is not to worry about from how far away your food came, but to walk--not drive--to the supermarket.
All this to be taken with a grain of piquant salt!!!