The more I read about local diets and foodshed eating, the more I wonder how to evaluate the wildly varying claims about food miles, carbon costs, etc. It seems obvious that some long-distance provender is less damaging in environmental terms than others, but it gets bewildering to try to figure it out, especially when you are standing in the grocery aisle looking longingly at a gleaming pile of limes. The trendier local eating becomes, the more alluring the advertising we see from transnational giants pretending to be mom-and-pop neighbors
Actually, that's one appeal of an arbitrary boundary like the 100 Mile Diet. Once you've set your parameters you can stop thinking about those individual decisions and exceptions and concentrate on enjoying the food that is available to you. Sort of like when you decide to settle down with one person and make it work.
But what I started out wanting to say was...I found a site that explains in detail the technical justification for its claims on environmental impact of a big variety of foods. It also has a tweaky but very interesting interactive map for local food producers in Lower British Columbia and Northwest Washington. I love this melding of high tech and local knowledge. Check it out.