Rahul sent me a link to this interview with ethicist Peter Singer on Salon:

In your book you say that socially responsible folks in San Francisco would do better to buy their rice from Bangladesh than from local growers in California. Could you explain?

This is in reference to the local food movement, and the idea that you can save fossil fuels by not transporting food long distances. This is a widespread belief, and of course it has some basis. Other things being equal, if your food is grown locally, you will save on fossil fuels. But other things are often not equal. California rice is produced using artificial irrigation and fertilizer that involves energy use. Bangladeshi rice takes advantage of the natural flooding of the rivers and doesn't require artificial irrigation. It also doesn't involve as much synthetic fertilizer because the rivers wash down nutrients, so it's significantly less energy intensive to produce. Now, it's then shipped across the world, but shipping is an extremely fuel-efficient form of transport. You can ship something 10,000 miles for the same amount of fuel necessary to truck it 1,000 miles. So if you're getting your rice shipped to San Francisco from Bangladesh, fewer fossil fuels were used to get it there than if you bought it in California.