There are good reasons to buy your fish, meat, and produce from local sources. It’ll taste fresher for one thing, and you’ll be supporting the local economy—-well, if the local economy is defined by a very large goddamn radius. But one thing it won’t do is save the planet. Remember that as you’re carving into your organic, free-range Heritage turkey from Whitmore Farm, thinking your Thanksgiving dinner is greener than thou.

Don’t believe me that the buy-local environmental dogma is riddled with ideological holes? Then I suggest you read (or re-read) Roberta Kwok‘s excellent examination of local vs. wholesale food over at Salon.com. Here’s the gist of it:

Despite the difficulties, scientists are now devising methods that attempt to calculate every waft of greenhouse gas for a given food product. That means examining a product’s entire “life cycle,” from fertilization and heating to packaging and storage. Fertilizer production, for example, is an energy-intensive process that can release copious carbon dioxide. And nitrogen fertilizer releases the greenhouse gas nitrous oxide after it is applied to fields. Refrigerating picked fruit for later distribution is another source of carbon dioxide emissions.

When scientists look behind the scenes, local food doesn’t always come out on top. A 2005 report for the U.K.’s Department for Environment, Food and Rural Affairs (DEFRA) found that growing local tomatoes caused more than three times the carbon dioxide emissions of importing Spanish tomatoes. The culprit was the glasshouse heating required to grow tomatoes locally.

In one of the most high-profile examples, New Zealand researchers reported in 2006 that some of New Zealand’s top food exports boasted less energy-intensive production than food produced locally in the U.K., even when the long trip was taken into account. Raising lambs on New Zealand’s grassy slopes required four times less energy than U.K. lamb, which relied more heavily on fertilizer, they said. The same pattern held for dairy, which used half as much energy, and apples, which used 60 percent.