As far as we Earthlings know, water is the foundation of life. From the primordial ooze to a fresh spring rain, we must have water to grow and survive.
But how do we get it when we’re out among the stars?
We can mine asteroids for minerals and metals. We can manufacture composite materials from known (and maybe newly discovered) elements. But that all sounds like thirsty work. Where can a guy get a drink around here?
Do we pluck frozen asteroids from the heavens, or chip away at the frozen surface of a moon like Europa? Since rising tides are literally drowning the Earth, is anything being done to desalinate and perhaps transport the seawater to other locations: the moon, Mars, etc.?
You could find water from all sorts of places. It could be in gas giants. It could be lurking on asteroids as you suggest. Water is actually fairly abundant. It just isn’t as abundant in a liquid form on worlds in the habitable zones. Despite the CoM map’s vast size, there are a relatively small number of habitable worlds for the given number of stars, and while many systems are home to humans despite not having habitable worlds, they are still quite hospitable thanks to frozen water sources in these star system.
As for earth’s fate, much of the effects of global warming have been stemmed by 3417. Much of the ice cap has been restored thanks to human intervention, and water levels have receded. Of course humanities human population on the homeworld has grown to towering levels (68 billion by 3417) so desalinization plays a role!