[mushufasa]

Differing regional environmental regulations is indeed a big problem.

One pet peeve of mine is locavores clamoring about emissions from transportation.

Food shipped overseas is not emissions intense at all. Huge tankers are __the__ most efficient means of transportation, emissions-wise. Pair efficient diesel with the physics of huge inertia over a frictionless medium, and gigantic economies of scale.

Usually, growing tomatoes in a greenhouse in Vermont is __more__ emissions intense than shipping them from Chile.

[darkpuma]

Eating foods that are actually endemic in your region is important. However I will admit the equation probably gets flipped if you live in a region with poor environmental regulation and have the opportunity to eat imported food from a region with better environmental regulation.

As for the matter of emissions, that's a complex issue. In the specific case of heated greenhouses, one must consider the source of the power being used to heat the greenhouse. Not all power is made equal when it comes to emissions. Some places burn coal, others use hydro (clean, but damming rivers causes habitat loss), others use renewables (great) or nuclear (clean and controversial.)

Frankly though food related emissions are going to be a small portion of all global emissions. What concerns me more is habitat loss caused by agriculture, and whether or not the region I'm getting food from has effective regulation in place concerning that (and if not, whether I have any chance of influencing the government in that region.)

[YUMad]

More efficient per mile, sure. But how about per total trip length?

[Xylakant]

The local leg via truck is likely to be much more energy intensive unless you live right next to a seaport.