The local food movement, and their new social category, locavores have done much to elevate too many awarenesses about the ethics of eating. But as I have long suspected, not too many of these folks were math majors.
It is not that the concept of food miles is wrong; it is just too simplistic, say experts. In fact, balancing your diet with its carbon costs turns out to be a fiendishly tricky business. Consider these two staples: apples and lettuce. The former are harvested in September and October. Some are sold fresh; the rest are chill stored. For most of the following year, they still represent good value - in terms of carbon emissions - for British shoppers. But by August those Coxs and Braeburns will have been in store for 10 months. The amount of energy used to keep them fresh for that length of time will then overtake the carbon cost of shipping them from New Zealand. It is therefore better for the environment if UK shoppers buy apples from New Zealand in July and August rather than those of British origin. [More]To be fair, some local food advocates have tried to adopt more rational approaches. This whole exercise points out how important it is to make market prices reflect all production costs - even externalities like environmental impact One reason I support a carbon tax, is locavores wouldn't have to preach to the unsaved - the price sticker would do it for them.
Sadly the near-universal abdication of fiscal responsibility by politicians means the only option for voters is to resist new taxes despite any attendant benefits simply because their elected representatives cannot be trusted with new income. Which is a shame, because some of the cost-benefit ratios are pretty low.