If you have time travel and your future is about to become uninhabitable, then you can survive by traveling far enough into the past, as in Poul Anderson's "Wildcat" and also in a
Star Trek episode, whereas, if there is time travel in a mutable timeline, then maybe you need a temporal police force, as in Anderson's Time Patrol series: two examples of time travel as a means to survival, the first covered by Anderson in a single short story, the second in a long series of stories and novels, and, since this a late night post, we will leave it there till the morning when I expect to finish rereading and posting about "Wildcat" -
tempus fugit.
