I do not think it means what you think it means

Stephen Dubner, on the Freakonomics blog argues in favor of specialization and against eating local. The argument makes some sense: transportation costs, according to some recent work, don't account for that much of the carbon emissions created for food. Here's where my understanding breaks down. Dubner describes making orange sherbet, which was expensive and produced crappy orange sherbet: unsurprising. He concludes from this that growing one's own food is likely to be resource-intensive in money, labor, and waste, and that therefore specialization is a better deal. Which, fine, but it's based on some fundamental misunderstandings of the local food movement.

1. Eating local doesn't necessarily mean growing your own. I certainly grow fairly little of my own food (the Gardener of course has a garden, with lettuce and greens and tomatoes and herbs), but I eat mostly local, including items like eggs and milk that are totally impractical for me to raise myself.

2. Specialization can mean different things. The farmers I buy from have a specialized job as farmers, but they maintain the ecological health of their farms by growing a variety of crops which they rotate, and by incorporating animals into their farms. So their job is specialized, but they are generalists within that specialty: being a true specialist as a farmer means planting a monocrop, which then exposes your crops to greater disease risk and reduces your ability to let the ecology do the work of keeping the land healthy. Dubner conflates specialization of labor with specialization of crop, and they're very different.

3. Bizarrely, Dubner argues that growing your own will rarely be cheaper. This is just untrue overall, although there will always be exceptions. Herbs are a great example: a window box with marjoram, sage, thyme, oregano, rosemary, etc will run you something like the cost of 2-3 bundles of each herb. There are certain things where that's not true, obviously (eggs and milk are easy examples, but corn is expensive and takes a lot of land), but Dubner doesn't really investigate the costs: he just assumes that it's similar to his orange sherbet. What's particularly funny is that the NYT food section has a current article about how people are gardening to reduce their food costs, which does include some actual information.

4. Growing your own means using excess capacity. Walk around any city: there's tons of space to grow food, including patios, vacant lots, roofs, windowboxes. Because this increases the net food growing capacity of the planet, growing your own, especially for city dwellers using it as a supplement, is a pretty clear benefit for overall efficiency. Similarly, Dubner claims that people are bad at growing their own food, but this isn't a fixed point: the best way to get better at gardening is to do it for a few years.

As an aside, if I were trying to do what Dubner did with the orange sherbet, but in an efficient way, the first thing I would do is abandon the idea that it needs to be orange sherbet, and instead make something with some excess: this week, that'd be strawberry-buttermilk ice cream with jam strawberries that you can sometimes get at the Farmstand and the buttermilk that's left in our fridge from making butter out of cream that was going to go bad. Part of the point of eating local and being ecologically efficient is turning waste into food. Compost, buttermilk, yogurt, jam, dried tomatoes: take what you have too much of and make it useful.