[0] https://en.wikipedia.org/wiki/Lebensraum

>but devil's advocate - is fascism worse than literal extinction?

That's the question everyone will have to answer, and it probably boils down to the core of that person's philosophy. People who say "no" though should really consider all of the ugly side-effects that result from all-powerful authoritarian entities being able to control lives on a micro level.

But I said "extinction". Meaning everyone - you, me, my kid, etc. dying, maybe horribly.

Why in the world do you think that democratic structures will make it intact through a descent into extinction. I'm not going to cite Mad Max as a sociological point, but society will break down under unmitigated global warming. When food and water safety cannot be met, law loses its authority. You can see this on a small scale after cyclone landfalls.