There are many reasons why people support the idea of “buying local.” (See here and here for a little more information). But the most prominent among these ideas is that buying local is somehow “good” for the environment. So, let’s focus on that one aspect of the “buying local” idea.
Here’s my query: if the ecolocals truly cared about the environment, they ought to support programs and institutions that demonstrably improve conditions or do less harm than others. So, if someone demonstrated to you that a truly global pattern of production and exchange was better for the environment than the local production and exchange idea you support, would you alter your position? (and yes, if my only concern was the environment and there was overwhelming evidence that local production made things better, I would reconsider my favorable trade position)
Why do I ask this? Because it is tautological that the only way buying local on a grand scale would be “good” for the environment is if buying local also meant buying less.
Forgoing the advantages gained by economies of scale in production of goods and services (especially agricultural goods) and the gains from specializing and extending the division of labor tautologically raises both costs and impacts on the environment. You might see this directly in prices. Locally produced goods and services are often more expensive (if local is a place other than where the good is naturally produced by market mechanisms). These higher prices are telling us that by definition more resources are devoted to its production than when prices are lower.
Patterns of sustainable production and consumption develop by encouraging the production of goods where the per unit costs of production and environmental impacts are smallest. Asking people to produce everything locally will require that food and other production will occur in areas unfavorable to its production (e.g. growing wheat in Arizona instead of Nebraska), and it will reduce the investments in capital goods and innovation that make production more efficient. For example, if you are farming for a small community of 5,000 people you are very likely using small scale agricultural machinery, even animals, that has a far larger per unit impact on the environment than machinery from a megafarm. Just because those environmental costs are dispersed in a buy local model does not mean they are smaller. In fact, research demonstrates quite clearly that transportation emissions and costs are higher when we move to a local model of production than relying on a naturally evolved model.
So, what is usually embedded in the buy local idea is that by doing so we buy less. It is only if we buy less that environmental impacts could be reduced. But this is second best if your true aim is environmental “improvement.” Environmental costs would be reduced even more if instead of buying less locally, we bought less globally and maintained the extensive division of labor that has developed. Will any/many localists openly promote “Buy Less” instead of “Buying Local?” I doubt it. Extra credit points if you can reasonably discuss why.