This is an article from The American Prospect that I thought was very interesting. Here's the link:
Below is the article that I cut and paste.
IT'S THE FOOD, STUPID.There's been a lot of talk lately about the carbon footprint of shipped food. And with good reason. The average American household burns through about 8.1 metric tons of greenhouse gases as a result of food consumption. By contrast, if your house has a car that gets 25 mpg and you drive 12,000 miles a year, that produces 4.4 metric tons of greenhouse gases.
The line, then, is that the prudent environmentalist will eat local in order to cut down on greenhouse gas emissions. Intuitively, that makes a lot of sense. Bananas shipped from Brazil can't be good for the environment. But two Carnegie Mellon researchers recently broke down the carbon footprint of foods, and their findings were a bit surprising. 83 percent of emissions came from the growth and production of the food itself. Only 11 percent came from transportation, and even then, only 4 percent came from the transportation between grower and seller (which is the part that eating local helps cut). Additionally, food shipped from far off may be better for the environment than food shipped within the country -- ocean travel is much more efficient than trucking.
As Brad Plumer writes, the striking takeaway is that "on average, replacing just 21 percent of the red meat in the 'typical' diet with fish or chicken does as much, emissions-wise, as buying everything in that same diet locally." That's not, of course, an argument against eating locally. Taste, farming practices, sustainability, and much else point towards local consumption. But buying locally raised meats doesn't get you off the environmental hook. If you're worried about global warming, changing what you eat is far more important than monitoring where it's produced.