If the earth is no longer habitable, what should humans do?

It can be said that if the earth becomes no longer suitable for human habitation at this stage, there is nothing that human beings can do, and if they say something unpleasant, they can only do nothing. Because mankind has not found a planet that is completely suitable for human survival, to say the least, even if such a planet can be found, there is no way for mankind to immigrate all of itself to that planet. Therefore, human beings should protect the earth, the only home where human beings can live!