Overpopulation is one of the driving forces of the climate crisis. We relieve the pressure on the environment with less people. If there are too many old people because of it, they can work longer, there can be more resources spent on them, or there can be more automation. We are on the way to defusing the population bomb. Why stop now?
Yes, I am one of those fuddy-duddies in my 70s who went to college in the hippie era. And I never really bought into the Population Bomb hype, to be honest. I am also a big fan of Julian Simon ever since the early 1990s. This “depopulation is bad” argument smacks of “quantity over quality” to me. I agree with Simon about “The UItimate Resource”. But we don’t really need to keep growing to achieve it. We need to get the best quality of life for everyone, regardless of the total population. I just happen to think that stopping population growth is not bad in and of itself.
Far-future effects are so hypothetical that they cannot be used as a determinant for our actions. The counterfactual branching factor is so high that your present action can only apply to a minuscule number of futures. Our time and effort should have an exponential decay—focus most of the effort on the present and (a/b)^y for each year where a/b < 1