But as jsnell said below this: A lot of people might like the idea of living on Mars when there is absolutely no risk of that actually happening. While I think

But as jsnell said below this: A lot of people might like the idea of living on Mars when there is absolutely no risk of that actually happening. While I think that we're still a good ways from pushing this planet to it's limit (at assuming renewable energies come online quickly enough to mitigate population growth), eventually we'll want more room. And living in contained units (underwater, in space, or on other planets, ) doesn't seem like a worthwhile solution. So we're either talking population control or making more livable space. Surely, a thousand years into the future, we don't want to only have one livable planet to our race. And (maybe I'm wrong but,) terraforming what we have seems more likely that traveling to other Earth-like planets. I'm not crazy enough to think that this is something we can overcome easily, or during my lifetime, but I think it's more of a "if we don't get started now, when?" type issue.