Salvation, and heroism...
When I was a kid, science was going to save the world. All the suffering I saw in the world was going to be dealt with. I was going to grow into adulthood in a place that was coming to resemble a utopia. I was going to live in a perfect L-5 colony, maybe, or go to Mars, if that was what made the most sense. Earth was doomed because of nuclear proliferation, but humanity would find its home in the stars, so tragic though Earth's situation was, at least there was still hope. Perhaps after the nuclear holocaust the ecosystem would eventually recover and we could go back. I always pictured myself being one of the people who escaped, of course.
And the fact is that from a conventional perspective, Earth really is in deep doo-doo. I don't know if global warming is really going to produce a runaway effect; if it does, it will be worse than any nuclear holocaust, and indeed we may detonate nuclear weapons just to stop it, because living with mutations and cancer is better than dying when your environment becomes completely inimical to life.
Even if Earth doesn't die in a nuclear holocaust, grey goo is always a worry, as is the ultimate plague. Our understanding of micro-organisms is getting so much better than it was; the ability to make a kiss-your-ass-goodbye plague is coming closer and closer to being a reality. So there are good reasons for wanting some additional ecosystems for backup.
The typical activist approach to this problem is to try to prevent the end of the world. And this is a good approach. I think it has some real hope of working, although if it does I think it will happen accidentally, not through planning - we will save the world, but we won't know how until we do it, and we may not even notice that we did it when we do it, except in retrospect. In order for that to happen, people have to be trying and learning.
But the people who want a backup are right too. It would be really good to make a backup, just in case something goes wrong. And the fact that no such backup has yet been made is frustrating and frightening. Unfortunately, space travel is completely impractical, because it requires so much energy. So our trips to the moon have been postponed indefinitely. Homo celestis has yet to be born. I don't blame people who took refuge in a scientific solution to the world's pain when we were kids for being sad about how little meaningful progress has been made on the world's systemic problems, because the need for a backup is growing, not shrinking. Science has given us the iPhone, which is really neat, but we're really not much closer to a real backup ecosystem than we were when I was a kid.
From my side, I will tell you what I see, though. There are too many chiefs, and not enough indians. The world is going to be saved one person at a time, not with some massive top-down program. The ending to this story, if it is a happy one, will be like the ending to V for Vendetta, not the ending to Deep Impact.
But being a single microorganism in a great movement is not as emotionally rewarding as saving the world through your own actions. So we all hold out for the opportunity to save the world in some big way. And we have trouble getting excited about all the opportunities we have to be a tiny part of the process of saving the world in little ways.
Bootstrapping the salvation of the world will not happen because someone gets up on a pulpit and finally preaches the sermon that everybody understands. It will come as more and more people choose to change how they act, and become role models for other people. Salvation will spread like an epidemic, not like a government program.