> Can you explain how focus on a local supply chain, say, as one element of Organic farming practice is detrimental to either of those things, [human] health or environment?

http://freakonomics.com/2011/11/14/the-inefficiency-of-local...

"Forsaking comparative advantage in agriculture by localizing means it will take more inputs to grow a given quantity of food, including more land and more chemicals—all of which come at a cost of carbon emissions."