It is now 2010, only 40 years from the middle of this century, when (there seems to be consensus) we may reasonably hope that the human population will have stabilized in the neighborhood of 9 billion. That's a huge number, to be sure, particularly since we were at 3 billion in 1960. Take a look at the Wikipedia page on world population. Between 1750 and 1850, the population increased by ~60%. From 1850 to 1950 we shot up ~100%, and between 1950 and 2050 even the "UN Low" projection shows an increase of roughly 200%. From 60%, to 100%, to at least 200% and then... 0%? Or negative? Hard to believe, really. Seems like 300% would be a fair prediction. And yet this notion of flat-to-down world population are not merely wishful thinking; there is already strong evidence that population growth is decreasing and may be zero or negative in less than 50 years. Wow.
The on-the-ground realities behind these growth rate numbers reflect massive cultural changes. The explosion of humanity shows a certain kind of progress toward things most of us want: improved nutrition, lower infant mortality, longer lives, better disease prevention, etc, for ourselves and our families. What I'm saying is that the population boom was not the result of some effective world wide growth campaign, but a combination of technology improvements in agriculture and health, getting the word out, and people making their own choices to adopt new methods.
Now we don't have to be Thomas Malthus to imagine that untempered growth would be a bad thing in the long run, and that slowing the pace is vital to avoid all kinds of resource shortages, etc. The growth came from people making predictable choices to take advantage of new options. Is there any chance that we can somehow make use of the personal choice dynamic to bring us to the reduced growth? Or will population be constrained through starvation and war driven by vast and excruciating shortages and through policies like compulsory sterilization? Maybe "all of the above"? It seems plain to me that the more that we can support and encourage the choice-based reduction in growth, the less we will face the tragedy of externally imposed reductions.
The Wikipedia page referenced above tells us that fertility is already falling regionally. Some of that reduction is the result of governance policies "encouraging" small families, but reduced growth is also present in areas without strict population policies. Large groups of people are having fewer kids for their own reasons, making much different choices than their parents and grandparents did. Much of that shift has occurred in the developed world. It is also beginning in the developing world. The cultural changes that motivate lower fertility are multifaceted and include reduced infant mortality, improved education and literacy, the empowerment of women, and a shift from an agricultural model based on child labor.
How is such massive cultural change instigated or mediated? How do we as individuals "choose our culture"? We are not simply our parents children, nor did we learn everything in school (particularly not in areas where even primary education is not guaranteed). Culture is not simply established by government or NGO educational programs, though these may help. Few of us learned to use the internet in a classroom, and yet somehow that behavior has spread, pretty much through personal choice. (By contrast, there's at least some evidence that cellphone usage norms may be learned in school 
)
I'm convinced that rapid cultural change is mediated by a zillion small and large individual decisions based on our experience in a world undergoing rapid macroeconomic change. Amidst turmoil and uncertainty, many will seek to take their destinies into their own hands to improve their situation by trying something new (nicely exemplified, as I've said before, by William Kamkwamba). The people who are successful will be imitated. If enough people can make the right kind of choices, we will have a chance to create a stable world through peaceful means.
But time is tight. Humanity must adopt new behaviors quickly to avoid the "hard landing" that it (and other species) will otherwise face in the presence of our current practices. Appropedia's founders (myself among them) believe that we can have lives that are both rich and sustainable. Today, much of the rich world is not sustainable, and much of the sustainable world is not rich. What can we learn from each other?
Global progress toward improving the human condition has always depended on technological advances coupled with a millions of individual choices. Our current reinvention also depends on individuals exercising self determination in the presence of awareness, knowledge and insight. Could we support the vital rapid reinvention through a massive information campaign? Alternatively, how much will progress be impeded if practical information is hard to find? Wikipedia has shown that large scale voluntary information sharing campaigns are possible and relatively cheap. Enlightened self interest shows that such a campaign is essential.
It's a matter of personal choice...
