Not sure if this is the right stack for this but:
I have been arguing with friends on overpopulation, several are convinced that Earth cannot sustain the current population. Without getting into all of the ways that we are destroying various ecosystems and polluting, I believe that if we were actively working to optimize the environment and how we use resources, Earth could easily handle many, many more humans.
Such as renewable energy, reducing waste, committing to reversing desertification, and so much more. But regardless of the behaviors we specifically change, looking at the raw chemistry of the planet, i.e. how much water, oxygen, carbon, plant life, and so on, there is some maximum amount of humans that can live healthy lives.