> perhaps "it's not optimistic enough" is a little bit of a reach of a criticism.

It's not about optimism, but being factual.

> national borders are unlikely to go away in the next hundred years

That's a strange take, because an argument often raised is that ecological migrants must be accommodated if entire countries become uninhabitable.

As borders are just imaginary lines in the ground, if there is indeed a climate emergency, I do not see why say people from the Indian subcontinent (shown preeminently in the interactive map) would have no rights to settle in the empty eurasian steppes.

Human lives matter more than imaginary lines caused by historical circumstances.