Worldchanging's Alex Steffen's got a good, thoughtful piece up about "peak population," the idea that we'll crest humanity's most rapid period of population growth and that it will — and should — slow down from here. I love this quote from Kim Stanley Robinson, speaking of birth control: "empowering women is the best climate change technology."
It would be a mistake, however, to fail to see peak population as a hugely important insight, because when we know that we are riding a wave of increasing numbers (and increasing longevity) that will crest sometime after the middle of this century, we can also see that
1) The longer population growth rates remain high, the more total people there will be on the planet when we reach peak population, so one of our biggest goals ought to be seeing to it by every ethical means possible that the wave of population growth crests sooner rather than later.
2) If we are successful in reaching peak population sooner, at a lower number of people, rather than later with more people, we will be much more able to confront the myriad interlocking crises we face — a comparatively less crowded planet is an easier planet on which to build a bright green future.
3) Since we know the single best way of bringing down high birth rates is to empower women by giving them access to reproductive health choices (including contraception and abortion), education, economic opportunities, and legal protection of their rights, empowering women ought to be one of our highest priorities. (As Kim Stanley Robinson puts it, empowering women is the best climate change technology.)
4) Our other main task is to preserve natural systems and transform human economies in order to best withstand this wave of human beings, avoid catastrophe and leave behind as intact a world as we can — to save the parts (including not just biodiversity but also the diversity of human cultures and histories) so that future generations have as many options as possible.
5) Our best hopes for both avoiding catastrophe and preserving our heritage all hinge on our actions over roughly the next two decades. In that time we have enormous work to do: create at least the model of a zero-carbon, zero-waste civilization; begin deep and widespread impact reduction here in the developed world; sustainably raise the prospects of those (especially women) living in the developing world; and preserve as many working parts of our planetary heritage as we possibly can. After that time, all of these jobs will grow progressively harder, trending quickly towards impossibility.