I will confess: I've read some wonky books about population, demographics, family planning, contraception and blah, blah, bleeping, blah. It looks suspiciously like Kristof either hasn't, or he wasn't paying attention. Virtually everywhere, fertility has been dropping, in poor countries, in rich countries, in secular nations, in Islamic nations, in places with government support for parents, in places with no government support for families. Etc. Kristof cherry-picked his sample country (the Democratic Republic of Congo) and then casually implies it is a widespread problem -- when these days, it really isn't at all. It's a problem in a very small number of countries, almost all of which are in Africa.
The solutions he proposes aren't horrible (education for girls, easily available, multiple methods of contraception, and for the Obama administration to participate). But honestly? I don't like it when white men from wealthy countries go tell poor brown women they should have fewer babies. At a minimum, it should be women going and doing it, and I'd really rather see local activists being assisted and supported than tourists from the US dropping in for a few days and then going home to tell their little story of travel in a foreign land and oh gosh it's bad over there, isn't it.
And before he goes off on that ohmigosh population growth thing, it would be nice if he perused Fred Pearce's _The Coming Population Crash_. Which is a really pretty good book about population, demographics, family planning, contraception and blah, blah, bleeping, blah, even if at times it does seem as if he is summarizing Matthew Connelly's excellent _Fatal Misconception_. But I doubt even that would help, because Kristof read Connelly's book, and missed more or less the entire point -- what he got, he dismissed as being entirely in the past.
Kristof is disturbingly creepy. Technically, it would appear that we share some political views (women should have access to contraception and have political and economic power etc.). But in practice, he strikes me as just a different kind of colonizer.