People are starving today because of bad governance and cultural ignorance and things like that.  When a country is well governed and the population is literate and the agricultural industry is not run by corrupt officials and people don't insist on so much meat, there is no problem providing enough food.  I constantly cite Vietnam as an example, but Japan and China and India and Indonesia and of course all of Europe and North America are examples.

Considering what Vietnam exports, it could easily feed three times its present population, and, believe me, the population here is dense.

As far as water, it is true that no one dare touch the water in Vietnam, either in the rivers or from the tap -- but bottled water is abundant and cheap.  The problem in Vietnam with tap water is a prejudice against chlorine inherited from the French -- and I will admit when I'm in the States I let my water sit for an hour or so before drinking it so the chlorine can evaporate out (in my case, though, it's taste, not a conspiracy theory).

It is obvious there has to be some sort of limit on the earth's carrying capacity, and I would agree that from an environmental point of view a steady population can be of help, but the fears are way overdone.  Besides, the way to control population, as we have seen over and over around the world, is to raise living standards.  When living standards reach the level of even less than half that of Vietnam, population growth takes a plunge.  Rigid birth laws are intrusive, autocratic, even fascist.

I want to comment too on the idea of our living in space.  I fully expect that to happen -- not so much colonizing the galaxy (although that could happen too) but building self-sustaining space cities, maybe tethered to the earth or maybe out there on their own.  This stuff, however, is centuries away.