[quote=@The Omnipotent Sphere]
<Snipped quote by Xilaw>

Have you read the OP? The whole goal of our character's is to prevent expansion onto other planets.[/quote]
Well, I didn't suggest people colonize other planets, rather they harness their resources and bring them to Earth. I believe I already read in the OP that our drones have been actively travelling through the universe. 

[quote]As for technology, with advanced filtering capabilities which would likely be present in the future water will be completely recyclable (read up on the ISS' water supply). As for food, genetically modified crops have already proved to be the way of the future in the mass production of food, as long as we limited food-waste we wouldn't have a problem sustaining a larger population (American throws away 40% of its food).
[/quote]
No matter how much we progress in technology our planet cannot sustain our ever increasing population. That's a simple irrefutable fact. Thomas Malthus, a revered economist, calculated that human population tends to grow exponentially whereas our ability to feed ourselves tends to grow linearly. I could make you a diagram to explain it if you like.
It's not just the way to make food, clearly in the OP there's no room to make it. The entire planet is one giant city, which is also nonsense since our current population can fit in a city size of LA. There's plenty of room for people on the planet.