-finite water supply
What? Since the dawn of time, the water supply on Earth has been almost constant. -demand for energy
This isn't a real problem. First Law of Thermodynamics anyone? We just need to figure out more efficient ways of producing/consuming energy. -overpopulation
Is also a fairly non-issue. Just move to Australia. -global warming
Not an issue either. If we can survive in space, we can survive on a hot planet as well.The real reason we must learn to survive in space, is that in 4-5 billion years, the earth will be engulfed by the sun, as it expands to a Red Giant. In fact we need to create fully self-sustained space stations, as our galaxy (and possibly our universe) is doomed, since stars have a finite (albeit long) life cycle.
This of course providing we can stop hating each other long enough to actually make it that far or alternatively embrace the genocide of everyone who isn't like us.