> it doesn't matter how great the farming practices are if the food is then shipped three thousand miles to my door. (Yes, the food miles notion is imperfect, but it's at least a reasonable first-order approximation of the environmental impact of your food.)
I don't think so. Transportation accounts for only 11% of the environmental impact of food[1], so that's not a first-order approximation of the true cost at all. It is not only possible, but is in fact often likely, that shipping food three thousand miles from somewhere where it was efficient to produce has less environmental impact than buying food with epsilon "food miles".
(Which means that the take-home message is: if you want to use food miles as a metric, you should generally only buy food that is grown as efficiently where you are as in the part of the world that grows it optimally.)
I don't think so. Transportation accounts for only 11% of the environmental impact of food[1], so that's not a first-order approximation of the true cost at all. It is not only possible, but is in fact often likely, that shipping food three thousand miles from somewhere where it was efficient to produce has less environmental impact than buying food with epsilon "food miles".
(Which means that the take-home message is: if you want to use food miles as a metric, you should generally only buy food that is grown as efficiently where you are as in the part of the world that grows it optimally.)
[1] http://pubs.acs.org/doi/abs/10.1021/es702969f