for National Geographic News
Being a "locavore" and eating foods grown near where you live may not help the environment as much as you might think, according a new study.
When it comes to global warming, focusing simply on where food comes from will make only a small difference, the study's authors say.
"In terms of the average American diet, 'food miles' are not so important as what you're eating," said study leader Christopher Weber of Carnegie Mellon University.
On average, food racks up about 1,000 food miles (or 1,650 "food kilometers") traveling from farms to processing or packaging plants before reaching Americans' dinner plates, the study estimates.
The whole supply chain—including delivering grains to feed cattle and delivering fuel to farms, for example—adds another 4,200 miles (6,750 kilometers).
Yet all that shipping, driving, and flying accounts for only a sliver of foods' climate impact—just 11 percent of the total—compared with the impact from producing the food itself, the study showed.
The research appeared last week in the journal Environmental Science & Technology.
It's What's For Dinner?
Weber and colleague Scott Matthews measured the greenhouse gas emissions related to producing different types of foods—beef, fruits, vegetables, chicken, eggs, and fish—and getting them to U.S. grocery stores.
They found that beef is responsible for about one-and-a-half times more warming from greenhouse gases per household than chicken or fish, for example.
"Dietary shift can be a more effective means of lowering an average household's food-related climate footprint than 'buying local,'" the study concludes.
"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 [greenhouse gas] reduction than buying all locally sourced food," Weber and Matthews wrote.
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