Things don't happen in a vacuum and trying to extrapolate current trends 100+ years into the future is a fool's errand. A couple decades ago everyone was worrie

Things don't happen in a vacuum and trying to extrapolate current trends 100+ years into the future is a fool's errand. A couple decades ago everyone was worried about the opposite problem. Neither of us has any idea what the new worry will be in a few more decades. The earth currently has billions more people than are necessary to keep humanity going; there's plenty of slack in the current system. Yes societies will have to evolve if birthrates stay low for a while, but they always have to evolve and if populations ever did drop precipitously low people already know how to make more babies.