This study is a must-read for anyone concerned with food politics. It’s one of the only studies done on the issue. Abstract and full text are available here: Food Miles and the Relative Climate Impact of Food Choices in the United States
For those not into the technical language of scientific articles, here are the basic findings:
1) Food miles are not an accurate way to measure a food’s ecological footprint. Transportation of food accounts for only about 15 percent of its ecological footprint.
2)Production, storage, whether a food is animal or plant, non-carbon greenhouse gas emissions, scale, and other factors account for about 83 percent.
3) An accurate picture of a food’s environmental impact needs to include all those aspects and that can be done much more throroughly with a life cycle assessment (LCA). Movements for ecological sustainability would fare much better if they used the LCA instead of the food miles model.
4) It is impossible to do an all-encompassing study on the climate impact of food. This study is based on the “average” US household. Unmeasurable factors might play a role in many situations. Despite, these findings point to critical issues regarding diet and ecology.
5.) For the average household, eating vegan food one day a week achieves more of a reduction in environmental degredation than eating local animal products every day. Or, more precisely: “The results of this analysis show that for the average American household, ‘buying local’ could achieve, at maximum, around a 4−5% reduction in GHG emissions due to large sources of both CO2 and non-CO2 emissions in the production of food. Shifting less than 1 day per week’s (i.e., 1/7 of total calories) consumption of red meat and/or dairy to other protein sources or a vegetable-based diet could have the same climate impact as buying all household food from local providers.”
I look forward to more work being done on this, and more conversation being had.