Small farms will somehow have to avoid current Co2 transport costs but that also assumes there is adequate farmland and water resources near markets. I don't think we designed our population centers that way but in third world situations maybe they have? By chance if not design.
The above bolded part points to one of the many issues I have with advocates of permaculture, hydroponics, home/balcony gardening, and other ways of growing food in cities, as solutions to replacing industrial agriculture.
Take into account that there are approximately 500 cities in the world today which have populations which exceed 1 million people. More than 30 of those cities exceed 10 million people, 13 top 20 million and 2 or 3 top 30 million. Tokyo has the same population as California! Take further into account where many of those cities are located - Phoenix and Riyadh are good examples. Then try and imagine a low-to-no carbon, sustainable, non-industrial farming way of feeding them.
It is just not going to happen.
Whether people agree or not with my point that industrial civilization cannot be sustainable I think we can all agree that there is no way that places of this scale can be made to work that way.
I have never seen an argument that I thought made sense which contradicted the conclusion that our vast population was the result of access to vast quantities of high EROEI fossil fuels and their application in industrial agriculture. It is simply not possible to grow enough food in a sustainable fashion to feed as many people as we have today. There are simply too many of them to move to where we could operate sustainable farming and food delivery systems. There is not that much good land in the world to feed that many people.
In a sustainable world Bruce's produce would be bought or traded for by people who walked over to his place to pick it up. That means we live in villages for the most part - not cities.