I don't think it'll come to that, fortunately. As mentioned above, much of the US's growth is due to broken borders rather than broken condoms. Since the population in the rest of the world will stabilize by the end of this century (and become more prosperous to boot), the migration part will gradually lessen as well.

As for having enough resources to support a billion people, I think we can do it. We're a lot bigger than China, a nation with twice as many people, with a lot more fertile land. As for water resources, we'd probably do a lot of desalination - we've got plenty of coastline. Bear in mind that technology is going to advance a lot during this century - far more than in any other century, if some folks are to be believed.

- Maha Vailo

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When you get down to it, Science answers how. Religion answers why. - hippietrekx