the world is not infinitely vast. it cannot support an ever growing population.
if we keep growing, we will consume everything that there is to consume on this planet, and then we'll be forced to migrate to another planet, or sack it for its resources to send back to earth.
but it is very unlikely that our planet would even last that long.
ecosystems will break down. energy sources will become more scarce as it takes more and more energy just to obtain the energy we would need to support the population.
domino effect. mass extinction.
the planet cleans itself and the remaining organisms left repopulate the world until it reaches a stable state and a balanced ecosystem.
So which do you prefer? Becoming that alien species that conquers worlds and destroys them in the process, then moving on in a never ending quest to consume and support it's evergrowing size and desire for McGriddles and HDTVs; or becoming extinct?
These are the only two options our civilization has.
Unless we get our heads out of asses and return back to the way our species lived for millions of years prior to our modern day life style; in harmony with nature, not in a battle against it.