The closest planet which it’s believed could possibly support human life is Proxima Centauri. It is only 5,880,000,000,000 miles away (give or take a million or so). The greatest speed man has ever achieved is 24791 miles an hour. So, if we could build a ship that could maintain that speed for the 237 million, 182 thousand and 848 years it would require, and somehow maintain life support and have no mechanical failures, humans could get there. At that point, there is really no way of knowing if it could actually support life. And, assuming that it could, the life it is supporting is quite likely to decide “there goes the neighborhood” and shoot us out of their sky.
When we destroy it to the point that it will no longer support our life there are no viable alternatives that aren’t science fiction— with an emphasis on the FICTION part.