Eat locally and seasonally; avoid air-freighted food. The fossil fuels burned to ship your lobster from Maine or your cherries from South America exact a heavy price on the environment. Flying food 5,000 miles releases more than 16 pounds of CO₂, while food that is transported less than 150 miles by truck produces less than a pound of CO₂ emissions. The issue of food miles can be complicated, however: In one study, tomatoes shipped from Spain to the U.K. had a lower carbon footprint than local hothouse tomatoes. Yet when you buy local, you're supporting nearby small-scale sustainable farmers.

The enthusiasm of the “locavore” movement is commendable, but going local won't solve it all. The types of foods you choose still make a tremendous impact. A 2008 study in the journal Environmental Science and Technology found that “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.”

Make a balanced choice: Eat produce in season, when it is less likely to have been shipped long distances. Whenever possible, favor local produce at the store.

Next: For fish, go lower on the food chain