Eat Local?

Eating locally grown food has been promoted as a way to reduce global warming. The argument is that food that is transported long distances results in unnecessary CO2 output. One argument against that is the productivity issue. Growing food in areas that are more fertile or suited to the crop in question may result in lower greenhouse gas emissions for the same amount of food even if you factor in transportation. Here's further evidence of that:

Christopher L. Weber* and H. Scott Matthews
Department of Civil and Environmental Engineering and Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
Received for review November 28, 2007
Revised manuscript received March 4, 2008
Accepted March 14, 2008
Abstract:
Despite significant recent public concern and media attention to the environmental impacts of food, few studies in the United States have systematically compared the life-cycle greenhouse gas (GHG) emissions associated with food production against long-distance distribution, aka “food-miles.” We find that although food is transported long distances in general (1640 km delivery and 6760 km life-cycle supply chain on average) the GHG emissions associated with food are dominated by the production phase, contributing 83% of the average U.S. household’s 8.1 t CO2e/yr footprint for food consumption. Transportation as a whole represents only 11% of life-cycle GHG emissions, and final delivery from producer to retail contributes only 4%. Different food groups exhibit a large range in GHG-intensity; on average, red meat is around 150% more GHG-intensive than chicken or fish. Thus, we suggest that dietary shift can be a more effective means of lowering an average household’s food-related climate footprint than “buying local.” Shifting less than one day per week’s worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food.

Shifting diet from red meat would seem a more effective way to reduce the GHG emissions associated with food. It certainly has other benefits as well.