Eat local, save the environment?

This article looks at the term "food miles," how far your food has traveled from farm to plate. In an era where environmental impact and carbon emissions are important components of the price of food, distance matters:

On its face, the connection between lowering food miles and decreasing greenhouse gas emissions is a no-brainer. In Iowa, the typical carrot has traveled 1,600 miles from California, a potato 1,200 miles from Idaho and a chuck roast 600 miles from Colorado. Seventy-five percent of the apples sold in New York City come from the West Coast or overseas, the writer Bill McKibben says, even though the state produces far more apples than city residents consume. (emphasis mine)

And yet, as it turns out, focusing on shipping distance alone obscures the overall environmental impact of a given meal:

Instead of measuring a product’s carbon footprint through food miles alone, the Lincoln University scientists expanded their equations to include other energy-consuming aspects of production — what economists call “factor inputs and externalities” — like water use, harvesting techniques, fertilizer outlays, renewable energy applications, means of transportation (and the kind of fuel used), the amount of carbon dioxide absorbed during photosynthesis, disposal of packaging, storage procedures and dozens of other cultivation inputs.

Incorporating these measurements into their assessments, scientists reached surprising conclusions. Most notably, they found that lamb raised on New Zealand’s clover-choked pastures and shipped 11,000 miles by boat to Britain produced 1,520 pounds of carbon dioxide emissions per ton while British lamb produced 6,280 pounds of carbon dioxide per ton, in part because poorer British pastures force farmers to use feed. In other words, it is four times more energy-efficient for Londoners to buy lamb imported from the other side of the world than to buy it from a producer in their backyard. Similar figures were found for dairy products and fruit. (emphasis mine)

Buying local does have other advantages. Shopping at an independent retailer keeps 45 cents of every dollar spent in the community, versus 14 cents for shopping at a chain or franchise store. There's probably a similar payback on local food. But if you're out to minimize environmental impact, it's probably better to grow food where it grows best, and to pay a fair price for shipping (e.g. such as a carbon tax on fossil fuel used in shipping).