Given a slow enough rate of change, species would adapt and migrate. Presuming there aren't farms, cities, roads, railways, dams and fences preventing smooth migration to the newly appropriate regions.

My concern is we're changing the climate at geologically unprecedented rates, likely far too quickly for species to evolve and migrate, even if we hadn't locked up 50% of the world's landmass for our own use. That will play interesting havoc with food chains no matter what former permafrost and arctic is freed up for use (with its own emissions load on melting).

Fair enough - so how are humans sustainable?

GP's point is that they aren't. We are looking down the barrel of a total ecological collapse, and the trigger has likely already been pulled.

I tend to agree, I was just curious where this discussion would end up. So, what should we do?

Start changing behaviour after the IPCC first report came in, in 1990. Waiting until we have not just visible, but dramatic and surprisingly early consequences is leaving taking evasive action in the car until the bodywork has started to crumple. I note that nearly all the surprises seem to be of things being far more or far sooner than predicted...

That leaves dramatic and expensive global scale action. We're not doing it. There's no sign we're thinking about doing it. Let the market resolve is the sole incredibly weak suggestion.

I don't think history is going to view citizens and politicians of the 21st century kindly. I can forgive and understand those contributing to the problem before say 1990, before the awareness was widespread. We've emitted more since 1990 than in the entire time before.

So a planetary scale game of chicken...