From a interesting article in the NYT that list "10 Things to Scratch From Your Worry List" here is number 3:
3. Forbidden fruits from afar. Do you dare to eat a kiwi? Sure, because more “food miles” do not equal more greenhouse emissions. Food from other countries is often produced and shipped much more efficiently than domestic food, particularly if the local producers are hauling their wares around in small trucks. One study showed that apples shipped from New Zealand to Britain had a smaller carbon footprint than apples grown and sold in Britain.
It's a shame they don't provide a link or source for the apple study. Yet, the article does give you hint about how the whole local vs. imported debate is not as straight forward as some may think.
