That almost goes without saying. Cities are already nasty places, and don't understand the concept of sustainability.

The best you could hope for is an internal split into towns and villages with live agricultural centres surrounded by dead zones.

Bulldozing houses is much quicker and cheaper than putting them up.

But anyone with a hankering for pastoralism needs to consider that a new dark ages will inevitable create a new war lord class, intent on reducing most of the population to feudal slavery just because they want to, and can.

The most likely outcome is a pre-medieval stockade system, with heavily fortified population centres in the middle of agricultural land, where the peasants are largely considered expendable.

You may be able to tend your homestead in peace in less densely populated areas, but it's not going to be an option within a couple of hundred miles of any reasonably sized city.