Let's get unsentimental for a minute: i'm not saying it would be fun getting there, but wouldn't this planet be a lot more comfortable with four billion fewer people?
I used to be fairly unconcerned about overpop, thinking that it surely is a self-limiting problem. Too many people? No sweat: food supplies crash, famine, many deaths, problem solved. This was before realizing the extent to which we are committed to misery, committed to moreness.
We don't seem to be able to stop having more and more babies, but we've run out of space. As the ASI quotient (assholes per square inch) ratchets up, something has to give. The much-vaunted preciousness of human life as well it should be since if it weren't, the most unworthy, which is all of us , would feel too threatened guarantees that all else matters less, even the planet itself. So goodbye salmon, tigers and bears. Goodbye ozone, forests and dependable friendly climate. More doesn't apply to you. More applies to precious humanity, especially to those with theological approval to outbreed the competition. So more Catholics, more Muslims, and while we're at it, more Mammonists to consume more widgets.
We will put bandaids on bandaids on the ecological and resource-scarcity crises that erupt so that we can keep having more but without consciousness, it is a zero-sum game. Quantity can only come at the cost of quality, and here is where our commitment to misery comes into its own.
The quality of the planetary environment will continue to decline, but we won't care or even notice. Because we'll have more golf courses, more TV channels, more SUVs and more tamagotchis, we'll believe life is getting better all the time, even as we furiously apply bandaids and complain about how things just ain't the same as they were. And it won't matter how squalid the planet has become. It just won't matter. It is hard to avoid the conclusion that we must be committed to some kind of stupid choice.
This is a pretty bleak vision which certainly overlooks many hopeful trends as we lurch toward the millenium. Your call. I'm getting out; whatever the fate of the planet and humanity and all that grand vision stuff, i can still save myself, in the sense that consciousness can still be a source of peace even if the planet self-destructs. And contacting this source of peace, one soul at a time, might be the best thing we can do for the planet, rather than adding to the seriousness and tension and clash of ideologies that are tearing it apart. I don't know.