Education, health care, decent jobs, family planning programs, wherever these are generously available, family sizes come down. The other thing that has to come down is consumption. The ecological footprint of the average American is 13 times that of the average Indian. The 4 million babies born in the U.S. this year will have twice the earthly impact of the 26 million babies born in India. If you know where to look, you can see how good lives can be lived with much less load on the planet.
Organic farmers produce high yields of healthy foods without chemicals.
Drip irrigation grows crops with higher yields using less water. Windmills and solar collectors and fuel cells produce power without crazing the climate. Best of all, many people are freeing themselves from the steady brainwashing of the advertisers and deciding that they actually have enough. Whatever the media do with the Day of Six Billion, I'd suggest that we real folks, each of us an infinitesimal drop in that huge sea, refuse to simplify or trivialize it, refuse to caricature each other as either the scourges or the conquerors of the earth, refuse either to despair or to rejoice. We know of the problems we cause each other and the millions of other creatures that co-inhabit our finite planet.