Why would anyone take the risk of messing with that?
It's as though they assume that there will be generalized devastation but there will be some "safe place" which some powerful group can defend and use.
Instead it's possible that maybe for one year New Zealand will be great, but then there will be no rain for 10 years, while previously uninhabitable Brighton (UK) will be a lush, tropical paradise for a couple of decades. Everyone will haul their gear to Brighton and massacre the indigenous, but then everything will change again, etc.
Or we could stop driving 2000Kg of metal to get to our jobs or buy a bag of chips and keep all the tourists at home that are destroying Venice and leaving their feces and plastic containers all over the Himalayas.