But if you want to sustain political policies that benefit the environment, you need to ensure that your political preferences carry forward into the next generation. The poor and uneducated are far more conservative than other groups, especially with regards to the environment. Understandably so as they're focused on getting ahead.

So long as there exists substantial income inequality in a nation, such as is the case in the U.S., the middle- and upper-middle class need to literally raise future generations of themselves. Otherwise they're de facto abdicating political power to the rich elite and poor masses. And even if eventually the poor masses produce what will become the new middle class, there can still be substantial regressions in political values in the interim, which in the context of accelerating global warming is extremely costly. We've literally seen this--as income inequality has grown in the U.S., and as the stable middle-class has declined, we've become a much more conservative nation.

There's no more effective way to perpetuate your values than through your own children. Education of other people's children is not very effective or efficient, at least beyond basic skills like reading and writing. Ask any teacher, especially teachers with children of their own. And in any event people who don't have children aren't engaged in those aspects of our society designed to socialize the young. If you are intent on educating other children, what better way than to have empathetic children of your own who can model your values and keep you productively engaged?

I'm not arguing that educated and conscientious groups need to somehow out reproduce everybody else, or even match the reproductive rate of other groups. I'm certainly not saying it's a genetic phenomenon, or that it's equivalent to genetic-based phenomenons in terms of the role of reproduction. But having no children whatsoever and persuading similarly situated people to abstain, well that's a different matter entirely.

The fact of the matter is that we know the more educated, wealthy, and independent people are--especially women--that the fewer children they'll have. We see it across cultures. That's good. But it also means that in the presence of disparities in those factors, there exists a dynamic that slows down the reduction in reproductive rate.[1] To accelerate the reduction in reproduction as well as other ecological pressures (reduced carbon consumption, etc), you have to strategically ensure that political policies which diminish inequality, and which in the interim directly mitigate global warming, persist and expand. In democracies where every vote is nominally the same, where educated groups have higher rates of voting and political participation, and where both political preferences and economic mobility are sticky across generations, you can't ignore the implications. At best advocating for fewer children is pointless as it'll happen regardless; at worst it's counter productive.

[1] I bet there's a correlation between rate of slowdown in reproduction with low Gini coefficients. For example, Japan. I haven't tested it but I'm gonna put it on my todo list. (Immigration is a confounder in terms of reproduction rate, but I bet it also tends to positively correlate with inequality, and in any event the destination for immigrants are richer nations with much higher per capita resource consumption... but I digress.)