The problem with talking about intentional population control is that everyone points and calls you Hitler. Worse, people use it as a vehicle for their nativist sentiments and say the problem is the unwashed brown hordes swarming the border. For the record, both are bullshit. (If you are inspired to leave some racist comment about immigration, please return to the Public Policy Institute of California report, first paragraph. Birth rate, not immigration, accounts for population growth in California.)
My hope is to avoid some of that by pointing out the scale of the problem of unintended births. As a first cut, simply getting people’s reproduction in line with their own desires would halve our projected population increase. That should not require state coercion. A state policy and real resources* dedicated to that would be beneficial all around.
You could go even farther, and without saying that anyone shouldn’t have children, create policies that delay desired children. Remember, a year or two of delayed emissions are valuable to us. Flattening the growth curve matters at any discrete point in the future. I was more optimistic about his option until I saw the PPIC report and this CDC report saying that mean maternal age at first birth is already pretty high. But you could target programs at communities in which women have children young. You could use the solution everyone offers for less-developed-countries, and educate the ladies. Forgiving student loans for Latina women who haven’t given birth by age 25 might bring their age at first birth up to the general population’s.
My point is that there are non-coercive options and a role for the state (like making birth control free and ubiquitous). The choice isn’t between doing nothing and firing up the sterilization chambers based on eugenics. There are also large environmental costs from maintaining the taboo on openly discussing population. We should be braver. We should bring it up and keep bringing it up.
*If you are wondering how much to spend, the cost of averted new dams would be a one-time $6-7 billion. So that would be break-even in one facet of environmental costs. If you start thinking about subway capacity or new airport runways we wouldn’t have to build, I think you can find some real money to spend. Adaptation to climate change is predicted to cost a few percent of GDP, or about twice the financial system bail-out, or twice the stimulus package, so there’s room to think big.