Eating local may be good for your sense of the type of person you are, or for your local growers, but locavores should be reminded it isn't necessarily a great good to the cause of energy conservation or greenhouse gases. Agricultural economists Jayson Lusk and F. Bailey Norwood in their essay "The Locavore's Dilemma" posted at Liberty Fund's "Library of Economics and Liberty" site, sum up:
The truth is that the energy expended transporting food is relatively unimportant. According to USDA-ERS data, consumers spent $880.7 billion on food in 2006. Only four percent of these expenditures can be attributed to post-farm transportation costs. One recent study indicated that over 80 percent of the global-warming impacts of food consumption occur at the farm, and only ten percent are due to transportation.7 After an extensive literature review, other researchers have concluded that "it is currently impossible to state categorically whether or not local food systems emit fewer [greenhouse gasses] than non-local food systems.
Reason's Ron Bailey wrote at length on the silliness of "food miles" obsession back in November 2008.