Not so, according to an op-ed in The New York Times. While there are many compelling reasons to eat local, monitoring your "food miles" won't always trim your carbon footprint:
... scientists reached surprising conclusions. Most notably, they found that lamb raised on New Zealand’s clover-choked pastures and shipped 11,000 miles by boat to Britain produced 1,520 pounds of carbon dioxide emissions per ton while British lamb produced 6,280 pounds of carbon dioxide per ton, in part because poorer British pastures force farmers to use feed. In other words, it is four times more energy-efficient for Londoners to buy lamb imported from the other side of the world than to buy it from a producer in their backyard.Of course this study is not a free pass to eat strawberrys in December. Instead, this op-ed reminds us to take a more nuanced view of farming.
For a study with a conflicting point of view, check out point #7 on 100milediet.org's list of 13 Lucky Reasons to Eat Local.