There is a very nice manuscript in this month’s volume of Environmental Science and Technology on the GHG emissions of different foods:
Weber, Christopher L, and H Scott Matthews. “Food-Miles and the Relative Climate Impacts of Food Choices in the United States.” Environmental science & technology 42, no. 10 (2008): doi:doi: 10.1021/es702969f.
They find that what you eat matters far more than where you buy from. Here’s the 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.
So climate researchers and your cardiologist agree: no red meat. (Does bacon count as red meat?)
Shipping food–or anything–is not a particularly polluting activity–not for individual goods anyway. It’s when we concentrate trips spatially–like the freight coming in and out of the Port of Los Angeles or for millions of trips in the LA basin, that sustain air quality problems despite the decades of improvement from engines and fuel.
But buying local still has a flavor advantage, no surprise there; globalization and localism still manage to be compatible, at least when it comes to GHG emissions.