This blog is part of our Inspired Ethonomics  series. Patti Prairie is the CEO of Brighter Planet, a startup whose purpose is to help manage our environmental footprint, you can follow via their blog 
Few movements have captured the liberal imagination like the local food movement. "Food miles" is becoming a household term, and a Google search for "locavore" returns nearly half a million results. But at a time when our nation and our planet are grappling with the prospect of devastating man-made climate change, we're in need of some perspective on what local food really means.
By one count the typical bite of food travels 4,200 miles as it winds its way through the supply chain. But delivery of the final food product to the grocery store accounts for just a quarter of that travel. The other three quarters comes from delivery of inputs to farms and factories.
That means that how locally your food producer sources his goods is three times as important as how locally you source your food. You may buy beef from a farmer just up the road, but if his cattle feed is trucked in from halfway across the continent (as most is), then what does "local" beef really mean?
Another caveat to local food is that if it's even just a little more carbon-efficient to produce elsewhere, that benefit can outweigh the transportation impact. Production contributes 45% of a meal's total carbon emissions, but transportation in the supply chain contributes just 6%.
Could we produce locally grown chocolate in Vermont? Yes, but the carbon footprint of raising a cacao orchard in a heated greenhouse would dwarf the emissions from shipping cocoa from the tropics. An extreme example, but even for more mundane foods, focusing your local eating on local specialties and being willing to import non-specialties can reduce your impact.
Finally, the real kicker. All the shipping of inputs to the farm, crops to the factory, and foods to the store contributes just 29% of your typical meal's transportation footprint. The remaining lion's share of emissions comes from your own driving to stores and restaurants.
That might seem implausible considering the 4,200 miles your food traveled to the store that's just blocks from your house. But traveling in the back seat of your station wagon is orders of magnitude less efficient than traveling in a densely packed tractor-trailer or cargo ship.
Local food can be fresher, tastier, and help build strong communities. But when it comes to energy use and climate change, it may do less good than you'd imagine. In terms of carbon emissions, minimizing your own food-related driving, meat consumption, and cooking energy should be a higher priority than minimizing food miles.
Brighter Planet (www.brighterplanet.com) helps people manage their environmental footprint. The clean-energy start-up is pioneering fresh green solutions that are accessible to everyone, fit one's lifestyle, and are fun to share. To date, more than 150,000 customers have used the company's climate change solutions, the Brighter Planet Visa debit and credit cards and Offsets by Brighter Planet, to invest in reputable American renewable energy projects.
Brighter Planet recently published a white paper  on food and climate change, entitled, "The American Carbon Foodprint: Understanding and Reducing your Food's Impact on Climate Change."