Food miles and greenhouse gas

Ronald Baily writes at Reason:

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.

The authors claim the cost of food transport works out to only 1% of US greenhouse emissions. It's also important to consider that those growing food in warm climates are often poor. Surely it is better not to make developing nations pay the whole cost of reducing carbon emissions.