What’s the impact of overpopulation? One is that youth bulges in rapidly growing countries like Afghanistan and Yemen makes them more prone to conflict and terrorism. Booming populations also contribute to global poverty and make it impossible to protect virgin forests or fend off climate change. Some studies have suggested that a simple way to reduce carbon emissions in the year 2100 is to curb population growth today.

Moreover, we’ve seen that family planning works. Women in India average 2.6 children, down from 6 in 1950. As recently as 1965, Mexican women averaged more than seven children, but that has now dropped to 2.2.

Traditionally, support for birth control was bipartisan. The Roman Catholic hierarchy was opposed, but Republican presidents like Richard Nixon and George H.W. Bush provided strong support. Then family planning became tarnished by overzealous and coercive programs in China and India, and contraception became entangled in America’s abortion wars. Many well-meaning religious conservatives turned against it, and funding lagged. The result was, paradoxically, more abortions. When contraception is unavailable, the likely consequence is not less sex, but more pregnancy.

Contraception already prevents 112 million abortions a year, by U.N. estimates. The United Nations Population Fund is a bête noire for conservatives, but its promotion of contraception means that it may have reduced abortions more than any organization in the world.