lucy and 102 asked the question:

“what are the chances that inhabitants of our major cities will wise up and stream into the countryside like a plague of locusts?”

Modern farms are vastly more efficient than 19th century family farms but are also much more energy intensive because of synthetic fertilizer, pesticides and farming machinery. Due to Peak Oil, I think it is possible that we could revert back to a 19th century farming economy. That sort of economy is stable but to get there, the world’s population would have to reduce significantly and then go into zero growth mode (agrarian fascism?), i.e. we can’t get there without first killing off several billion people. Also, once we revert back to that economic mode there would be no turning back to an energy intensive, high population density urban based economy. The high population density economic mode requires either an abundance of nonrenewal energy or a major new energy source, e.g. nuclear fusion, etc. However the research and development infrasturcture necessary to develope totally new energy sources would no longer exist if a population collapse had occurred followed by the economy going back to pure agrarian. This is a classis example of “hysteresis”.

What’s currently happening during our generation’s watch might be the worst thing that has ever happened in human history.