> if you're willing to forgo having a family, quite likely for good.
Kids you have now will die around 2100 or so. Even if we avoid nuclear annihilation, as seems increasingly likely, the world will be a pretty awful place by then.
Barring total catastrophe, I simply don't see how a relatively stable population with incredibly advanced automating technology and biotechnology would be incapable of "fixing" the world.
A small minority will be perfectly capable of "fixing" their bit with multi-billion-dollar storm surge protection, desalination, etc. Given that the rest of humanity will be motivated by the threat of death, I wouldn't rule out total catastrophe. There are levels of survival you should not be willing to accept.
There are many reasons to do things that have nothing to do with the state of the world in 2100. For example, there may be value in improving the remaining lives of people who will be dead before then. Think about it.
Kids you have now will die around 2100 or so. Even if we avoid nuclear annihilation, as seems increasingly likely, the world will be a pretty awful place by then.