By request from BenS.
We do, of course, want to have some system of ensuring that the 70 odd million people of the country manage to gain enough food to keep themselves alive. We do thus want to have some sort of system that does this.
We would also like said system to be as robust as possible. For we know what failure of the food production and supply system means, famine.
So, what system is it that we should have?
The obvious point about agriculture is that it is dependent upon weather and other conditions in the place where it happens. It is possible for there to be infestations, droughts, floods, which entirely wipe out all food production in a specific geographic area for an entire year, sometimes even longer. Ireland and potatoes is only one such example.
Thus a robust food system gathers in food from many different geographic areas. For that is the manner in which we can gain access to the needed calories even if production in one area fails. This is true not just of us of course, it’s true of everyone.
Imagine, just to invent some numbers, that there are 100 food producing areas around the world and 100 food consumption areas. The most robust system possible would have each of the 100 areas gaining 1% of their food supply from each of the 100 producing areas.
This isn’t all that far off the number of countries in the world. If insurance, robustness, were out only determinant then we would want to have very much more international trade (or at least, across geographic areas) than we do now.
Now, of course, robustness is not the only desired feature of a food supply system. We would also like to have as much robusity as we desire at the least economic cost. So we are going to balance transport costs (there’s little point in hauling turnips around the world while the transport cost of coffee is an irrelevance) against that desired robusity.
But if insurance were what we were after we would not be supporting domestic agriculture. We would, instead, be supporting agriculture in other geographic areas. Thus the idea that we must cosset domestic agriculture as a method of insurance is entirely and completely the wrong answer.