It’s a commonplace among some environmentalists that an oil- or carbon-constrained world is one where it’s prohibitively expensive to ship food long distances, and therefore people should eat local. For example, James Kunstler argues that cities will shrink and people will return to locally grown agriculture. For the benefit of society, let me debunk this fantasy with some hard numbers.

Suppose the price of diesel rises by $20 per gallon – $5.25 per liter. This is somewhat higher than the E3 Network‘s 95th-percentile estimate for the economically correct carbon tax in 2050, and twice as high as the estimate for 2010. It could come about due to an apocalyptic oil shock, though such a world and a world with a very high carbon tax are mutually exclusive. Today’s Class I freight trains are capable of moving about 450 short tons of freight one mile on one gallon of diesel – about 170 ton-km per liter. (Large cargo ships are about equally efficient, so this holds equally well over oceans.)

Let’s now look at rice, a very cheap retail food item that can’t be grown in every climate and is thus vulnerable to an increase in price that’s essentially constant per unit of weight. Under the above assumptions, shipping rice from Arkansas to New York, a distance of about 2,000 km, would require an extra $60 per ton. The actual retail price of rice in the US is around $1,700 per ton, so the oil shock would raise the price of transporting rice long-distance about 3.5%. First- and last-mile transportation at both ends uses trucks and would become much more expensive, but this would be equally true of long-distance food shipping and locally grown food.

This actually overstates the supposed problem of shipping food across regions, because high fuel prices lead to both higher efficiency and lower consumption. In 2009 BNSF said it would take $10 billion to electrify its mainline network, including purchasing dual-mode locomotives, and pegged the breakeven point for such a venture at $4/gallon gas. A carbon tax would also cause the source of such electricity to shift to greener sources than coal.

While locavores insist on shaving off the small, small portion of their carbon footprint coming from food transportation, many ignore the much larger issue of what they eat. Not all – the environmental movement is full of vegetarians – but the attitude that buying local is more helpful to the environment than avoiding red meat is sufficiently widespread that it’s important to note that the opposite is the truth.

Everyone should read the study linked in the above paragraph. Even when accounting for the full transportation cycle of food, including fertilizer and other materials, transportation is a small percentage of food emissions. Ruminant animals emit large quantities of methane; large mammals hog feed and thus require more fertilizer and energy to grow; manure adds more emissions of nitrous oxides and methane. As a result, red meat consumed in the US emits 22.1 kg-equivalent of CO2 per kg. The average carbon cost posited by E3 – $400 per ton, one fifth the apocalyptic amount used in the rice transportation calculation – would tax red meat $9 per kg, $4 per pound, roughly doubling its retail price.