Generation Bye-Bye

I read something the other day that said by 2050 or so we will have 9 billion people on the planet. Can the earth actually provide enough air, water and food for that amount of people? I'm sure some scientist somewhere has figured out how much air and water and food a human requires a year to just survive and they know how many can survive.Are carbon based fuels only a small part of global warming and the large part is too many people? I don't think we have to worry to much about aliens taking over the planet there is not going to be anything left soon. We could put up a sign however "THE EARTH IS FULL GO HOME!"Think about it, one theory put forth recently was that Mars had life and it destroyed that planet but before it died it sent colonists to Earth. And now we've destroyed this planet. Don't say we haven't we can't even agree on anything even on a small scale how could we ever agree on the correct way to save a planet? Nice legacy for the next few generations which one will be named "Generation Bye-Bye"?