Migrant carbon

I'm doing background research for a story on migrant workers with my colleague Jeff Carolin right now, and yesterday we went to Branford to see a UFCW-funded support centre. Much of the food produced in Ontario is actually planted, picked, etc, by agricultural workers from Mexico and the Caribbean through the SAWP program. There are about 18,000 such workers in Canada, of whom about 16,000 work in Ontario. They fly in for several months a year and at the end of their work period are flown back home. Obviously, conditions are often pretty grim. What occurred to me just the other minute, though, is that the fact that they're flown in really changes the way we calculate how much carbon it 'costs' to produce local food. The 100-mile diet is based on the idea that locally-grown food requires less carbon to be transported here than from California, Spain, South Africa, or wherever else it might be grown. But to what extent does flying in the labour change the equation? Could it possibly even tip it to another preference? Surely, it mitigates the gains. When George Monbiot's book comes out tomorrow with plenty of figures, maybe I'll be inspired to actually do some of the math. But probably not.