[quote=@Fatal Error 1337]
Interested.

Also, how much have the remaining powers began trying to reclaim the territory around their cities or elsewhere? I'd imagine there's at least some area that's protected since feeding several million people is kind of hard without some sort of agriculture. 
[/quote]

Indeed. And THANK YOU for raising this point, I saw an answer to this years ago and was just reminded of it :D
There would have been aggressive campaigns earlier on to reclaim as much territory around each safe bastion to re-start agricultural efforts, but a considerable lack of space would demand for new solutions, such as the idea of vertical farming: 

[center][img]http://www.ecofriend.com/wp-content/uploads/2012/07/editt3_lE7Ou_69.jpg[/img][/center]
[center][img]https://wsunature.files.wordpress.com/2011/04/vertical-farm-vegetables.jpg[/img][/center]
[center][img]https://raddblog.files.wordpress.com/2010/03/evolo_winners_2010_skyscraper_competition_2b1.jpeg[/img][/center]
[center][img]https://raddblog.files.wordpress.com/2010/03/evolo_winners_2010_skyscraper_competition_9.jpeg[/img][/center]
[center][img]http://www.evolo.us/wp-content/uploads/2013/03/0094-water-rebalance-2.jpg[/img][/center]


And no. I have NO IDEA how that last image works as far as staying up-right goes.