See, most people do look at all those issues, and still have children. I mean hell, is it very pleasant the entire time of the pregnancy? Is giving birth fun? Fuck no, why the hell do you think they give lots of people Epidurals? I see it as the single only thing that I should ever achieve in my life. The single only true expectation for any human being. I mean, in the bigger picture, life is worth nothing if you don't contribute to the future of your race. Is any one single squirrel worth anything? No, but if it has a kid, then the race can continue, and that's what's important really.
Sure, we can debate this till the end of time whether humans have any reason aside from reproduction, but if you look at how every animal is programmed, even humans, the only things that we really do are live, and have children, the rest of it is meaningless crap. Sure, we shape the earth, but will that matter 10 000 000 years from now? Not unless the human race is still alive in one form or another.
Sure, I'll be dead in 10 000 000 years, but maybe by then the human race will have progressed from this dark time in the earth's history, where we abuse the planet and refuse to acknowledge the damage we're doing. But by that time, we'll have passed this time, and gone beyond where we are now. I'd say whether I'm dead or not, I'd rather that than humanity not existing past 2100 and the world erasing nearly all signs that we ever lived here.
Oh, and spec, I suggest you split this into a different topic.