Thoughts about action on climate change can lead on to thoughts about population ethics. If you worry about sustainability, it’s not diffiuclt to wonder about the resources people use, as well as the number of people who use them. The population of our planet is growing and will continue to grow, all the while our resources will shift, diminish, and otherwise change as our climate changes. The UN estimates that the teeming masses will increase from 6.7 billion to 9.2 billion by the year 2050. There were only about a billion and a half people on a comparatively roomy planet just 100 years ago. The jump is more than staggering. You can wonder about the consequences. The UN, for its part, just called for more family planning.
There’s a solid moral kicker in the UN’s call for action which has to do with the welfare of women. Usually, the philosophical action with regard to population ethics has a lot more to do with human welfare generally. What’s better: a number of very happy people or a larger number of people with just-tolerable lives? A few people on cushions or a lot of people picking through the dirt? Parfit argues that the repugnant conclusion is difficult to avoid. If what matters is human welfare, then you get more of that with lots of barely tolerable lives as opposed to a smaller number of well-off people. There’s an interesting summary of the problem and replies here.
I’ve got the horrible feeling that the repugnant conclusion is irresistible, so long as we suppose that our thoughts about human welfare as such are on a par with our thoughts about an individual human’s welfare. I can’t help thinking, too, that these sorts of thoughts aren’t quite on a par — anyway it will take some work to think the whole thing through. Maybe this is yet another instance of our global worries outstripping our capacity to understand things locally. We’re not bad at coming to conclusions about what’s best for you or for me or even for quite a few of us. We are in danger of falling face first when we think too quickly about what’s best for all of us. We can do better, but maybe it requires hanging looser, conceptually, and that’s not an easy thing for something like the UN to do.