I agree. It will be migration from uninhabitable regions that will cause a major world population crisis.
It seems that Prof. Albert Bartlett (RIP) was correct in his prediction that with overpopulation or over-use of resources the people will need to curb one or both or Nature will do it for them.
This video is an absolute must for anybody that is concerned and wants to know how and why this is happening. It is called the Exponential Function!
and if that is not quite clear enough, You may want to watch this classic that predicts which species will survive the anthropogenic extinction event that is currently forming and is called the Sixth Extinction event.
This is what’s awaiting mankind.
Ever heard of Covid and MonkeyPox? As population density increases in habitable areas so will other critters and they don’t care about civilization. They care only about survival.