Celebrating Earth Day

April 22nd has been Earth Day for the past 41 years, with a focus on the sustainability of human existence on our planet. That speaks directly to the interaction of population and the environment. The emphasis has generally been more on the latter than the former, but they are clearly both very important. ABC News has a nice story on reducing your carbon footprint, keeping in mind that where you live will importantly determine the nature of your footprint, and what you can do about it.
My own involvement in Earth Day goes back to the very first one in 1970. As a PhD student in Demography at the University of California, Berkeley, I was invited to address what turned out to be a very large outdoor gathering on the campus of California State University, Fresno. My talk was "Who Lit the Fuse on the Population Bomb?" and of course the answer was "look in the mirror":

Europeans and Americans are responsible for the world's population problems. It all began 200 years ago in the early days of European and American economic development...[you know the rest of the story if you've read my book]

I used the opportunity to push for change, keeping in mind that in 1970 the average woman in the United States was giving birth to 2.5 babies, virtually all of whom would survive to adulthood. Fertility was on the way down, to be sure, but it wasn't clear in 1970 whether or not that was a long-term trend.

We should definitely advocate for the immediate removal of all discriminatory barriers in education and in the professions [remember that this was the first year that women had been admitted as undergraduates at Princeton]. If you can get a woman out of the house and reward her with financial gain and social and economic prestige, then the social and economic costs of having additional children are going to increase for that woman and she is far more likely than ever before to prefer a small family.

I couldn't have said it better myself.