Year round fresh or not

NPR is doing a series of articles on the North American Free Trade Agreement and its effects on Mexico, Canada and the US.  Today's concerned the increasing availability of Mexican fresh vegetables 365 days a year in the other two countries.  It was done in a light hearted way, but it raised some serious issues for all concerned.   The food safety issues are way overblown, and from personal experience, I can say I would trust the Mexican exporters at least as much as the average American or Canadian grower.  Mexican agriculture has come a long way, guided in part by California growers who have poured millions into state of art of facilities.  Since the laborers are the same on both sides of the border, in many cases, the Mexicans have better food safety.  The larger issue is the breezy assumption that we should have tomatoes, string beans, squash, etc. available every day all year long.  Many people, myself included make a living from this trade, but I at least have a nagging feeling the whole trade is unsustainable in the long run.   The entire enterprise on both sides of the border is built on cheap fuel and cheap labor as well as a transportation infrastructure which is crumbling and not being rebuilt in a timely fashion.