Trade is not intrinsically a bad thing: moving flour slowly (train and sail boat will do!) from continental Europe to Ireland and shipping meat back seems sustainable if you're not assuming civilisational collapse. Flying lettuce around the planet is another issue, of course.
I guess what I'm thinking here is some form of subsidiarity for food - it should be produced as locally as makes sense. I suspect a lot of this would be sorted out simply by pricing the externalities into the shipping and production methods. Maybe a properly regulated market is the best way of doing the job?
What is efficiency?
Understanding also that regional policy, (eg CAP), can deal with the coordination of a lot of the differences between local capacities.
How far do you think that by "efficiency", you are in fact thinking of comparative advantage?
Isn't comparative advantage more-or-less about efficiency?
What kind of efficiency is comparative advantage about?
However, an urban market ... whether a market in a city or the market consisting of a small town ... is an essential element in sustainable agrarian development, so the level at which food self-sufficiency becomes a goal to consider adopting is the local region, consisting of an urban core and its rural hinterland.
Of course, legalists always want boundaries for definitions, and so units of analysis like local regions give them hissy fits, because its hierarchical ... one local region consisting of a small town and surrounding countryside is part of the hinterland consisting of a small city and its surround small towns and countryside, and that is part of the hinterland of a large city and its surrounding small cities and their surrounding small towns and countryside.
And of course in many high income nations we have planted large, difficult to heat and cool single occupancy homes directly across that countryside, so we have to learn how to plant around those kinds of obstacles.
Every large nation must aim for food self-sufficiency. All of its main regions must aim for as much food self-sufficiency as it can achieve, and some of its regions must arrive at a surplus to the extent that some of its regions fall short.
And every local region must aim to be an active center of agriculture development in its rural hinterland ... even if the peasantry in the rural hinterland presently drive SUV's to work in cubicles eighty kilometres away. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
