>> Nuclear fallout would be bad for people, but tends to be less harmful to short-lived things.

I could see 'fallout zones' reforesting, a la the Black Forest of Germany or the wolf-infested woods of European fairytales. <<

Everything is rewilding. With a much smaller number of humans, trees regrow and wildlife flourishes. They'll take some local damage from fires, chemical spills, etc. but overall the world is much better without humans and it recovers astoundingly fast. Nobody expected the wildlife boom in Chernobyl -- even I didn't, this level of resilience is atypical but delightful.