When my daughter recently returned from a class trip to a farmers' market, she handed me a vocabulary list: "Food miles," one entry read. "The distance a food must travel from farm to plate. The farther the distance, the more impact on our environment (transportation pollution) and the more need to preserve and package the food."

The concept of food miles is easy to grasp, and many consumers concerned with their earthly footprint have grasped it hard. But recent studies show that transportation, on average, consumes far less energy than producing and processing food. So focusing exclusively on eating locally, writes James E. McWilliams in Just Food: Where Locavores Get It Wrong and How We Can Truly Eat Responsibly, is not "a viable answer to sustainable food production on a global level."

McWilliams, a history scholar who casts himself as a contrarian, frets about "locavores" because he considers them a threat to progress. He worries they'll realize too late that their dreams are unrealistic, and they'll miss the chance to "regroup and pursue more achievable approaches." (Never mind that the local-food movement never pretended that eating locally-or even regionally-would, on its own, move the world toward food security.) Instead, to grow more food on less or the same amount of land and to feed an eventual world population of nine billion, McWilliams recommends judicious use of both genetically modified organisms and the synthetic chemicals of conventional agriculture. The risk of synthetic pesticides has been overstated, he asserts (indeed, they're much safer now than in Rachel Carson's day), while organic agriculture's reliance on chemicals has been understated. Just because a toxin is natural, he says, doesn't mean it's less worrisome.

Like other proponents of genetic modification, McWilliams claims that relying only on organic agriculture, which he says "generally" yields less per acre than conventional farming, will diminish biodiversity as farmers clear rainforests to plant. But the case is far from proved; the question of yield remains one of the most debated points in agriculture. Inarguably, organic methods regenerate soil over time, while conventional methods tend to deplete it. And aren't we already clearing rainforests-to grow genetically modified soybeans to feed factory cattle?

Although McWilliams gives locavores credit for raising awareness, he also calls them "cowardly" for focusing on themselves instead of the potential benefits of globalization. If we deny Africans our biotechnology, they will be left unable to mass-produce their own food (or have any to trade) and will still need us to feed them. In April 2008, the United Nations International Assessment of Agricultural Knowledge, Science and Technology for Development came to the opposite conclusion, recommending that developing nations base their future food production not on genetically modified organisms but on agro-ecological and sustainable strategies.

McWilliams does promote,sometimes with barely a sentence, many sound and noncontroversial solutions: renewable energy for powering food production, a meatless diet, efficient transportation, the recycling of agricultural waste, and the use of life cycle assessments to make better food choices. But almost all of these ideas have been covered in other, less propagandistic books. Ultimately, Just Food makes a shallow read: McWilliams attacks locavores, who turn out to be straw men; stakes out a slightly provocative, nonideological middle ground in the debate between high yield and high sustainability; then joins the food-movement chorus in calling for specific reforms. How contrarian is that?