Ronald Bailey looks at The Food Miles Mistake:
So just how much carbon dioxide is emitted by transporting food from farm to fork? Desrochers and Shimizu cite a comprehensive study done by the United Kingdom’s Department of Environment, Food and Rural Affairs (DEFRA) which reported that 82 percent of food miles were generated within the U.K. Consumer shopping trips accounted for 48 percent and trucking for 31 percent of British food miles. Air freight amounted to less than 1 percent of food miles. In total, food transportation accounted for only 1.8 percent of Britain’s carbon dioxide emissions.In the United States, a 2007 analysis found that transporting food from producers to retailers accounted for only 4 percent of greenhouse emissions related to food. According to a 2000 study, agriculture was responsible for 7.7 percent of total U.S. greenhouse gas emissions. In that study, food transport accounted for 14 percent of the greenhouse gas emissions associated with agriculture, which means that food transport is responsible for about 1 percent of total U.S. greenhouse gas emissions.
Food miles advocates fail to grasp the simple idea that food should be grown where it is most economically advantageous to do so. Relevant advantages consist of various combinations of soil, climate, labor, capital, and other factors. It is possible to grow bananas in Iceland, but Costa Rica really has the better climate for that activity. Transporting food is just one relatively small cost of providing modern consumers with their daily bread, meat, cheese, and veggies. Desrochers and Shimizu argue that concentrating agricultural production in the most favorable regions is the best way to minimize human impacts on the environment.
Local food production does not always produce fewer greenhouse gas emissions. For example, the 2005 DEFRA study found that British tomato growers emit 2.4 metric tons of carbon dioxide for each ton of tomatoes grown compared to 0.6 tons of carbon dioxide for each ton of Spanish tomatoes. The difference is British tomatoes are produced in heated greenhouses. Another study found that cold storage of British apples produced more carbon dioxide than shipping New Zealand apples by sea to London. In addition, U.K. dairy farmers use twice as much energy to produce a metric ton of milk solids than do New Zealand farmers. Other researchers have determined that Kenyan cut rose growers emit 6 metric tons of carbon dioxide per 12,000 roses compared to the 35 tons of carbon dioxide emitted by their Dutch competitors. Kenyan roses grow in sunny fields whereas Dutch roses grow in heated greenhouses.
(I’ve discussed the localvore’s dilemma before.)