I agree with the gist of what you're saying, but I think you're leaving out some details.

We know that other non-local products can be made cheaper because they are in localities that are lax on labor laws and environmental protection.

So the notion that it's simply about efficiency is in my opinion a bit reductionistic. As an example, to make my point... I would use a different word than "efficiency" to describe someone who uses slave-labor to push costs down.

So when buying local, at least you know which standards the producers are held to. It's the same with Bio/Organic/Free-trade products.

That can be a factor, but simply making things in bulk is a huge efficiency gain even with the exact same worker/environment protection.

And on top of that you have transportation efficiency to take into account. A remote farm can send full trailers of product to a distribution center, which then sends full trailers carrying multiple products to stores. A local farm can't send a full trailer of apples to a local store, it has to do much less efficient things.

Evolution is perhaps the best example of how being inefficient can be hugely beneficial in the long term.

By comparison, "just-in-time" shipping is an example where the efficiency removes those margins. But that's orthogonal to how far the food ships. You can have similar-sized buffers either way.

I suppose that it's true about the large numbers of trucks, but wouldn't those only be reallocated to the detriment of providing other goods? And what happens to all our excess flexibility if severe oil shortages come to pass? Looking closer to the origin,the centralized model leaves us more susceptible to local droughts and floods (because everyone's produce comes from Salinas and watsonville), infectious diseases in livestock herds, and fungus that can cripple the entire crop of a particular fruit (because we've reduced the number of varieties by nine tenths or ninety nine hundredths.)

I agree, but certain types of dependencies are much riskier than others.

> I suppose that it's true about the large numbers of trucks, but wouldn't those only be reallocated to the detriment of providing other goods?

Yes, but what's the detriment of emergency-increasing local shipping? Probably at least as bad.

> And what happens to all our excess flexibility if severe oil shortages come to pass?

Local shipping takes more oil in many cases.

> Looking closer to the origin,the centralized model leaves us more susceptible to local droughts and floods (because everyone's produce comes from Salinas and watsonville), infectious diseases in livestock herds

Instead of a major shortage leading to deaths in one area, while everyone else is fine, it turns into a slight supply reduction over the entire country.

> fungus that can cripple the entire crop of a particular fruit (because we've reduced the number of varieties by nine tenths or ninety nine hundredths.)

That is definitely a major problem, but is also unrelated to how far you ship. Megafarms could plant 50 kinds of tomato efficiently, if they wanted to.

http://getmoreeducation.org/Content/Modules/Module1/1_Coley_... https://geneticliteracyproject.org/2016/07/25/organic-vs-con...

I am unaware of such studies for small farms versus large farms.

The kind of buying local that you need campaigns to encourage people to do, is generally either more expensive or poorer quality than the non-local alternative.