David Skrbina (Senior Lecturer in Philosophy in the Department of Philosophy at the University of Michigan) (2020): “A world of, say, 5 billion people is more likely to be sustainable than one of 10 billion; and a world of 1 billion is likely more sustainable still. All things being equal, a world with fewer people will allow for a more robust planetary ecosystem, and a higher quality of life for humans, than a world with more people… First, we have been pumping carbon gases into the air for over 300 years, and neutrality only means no further additions; at some point, we need to start pulling carbon out of the air, and return to a stable condition. We need a “carbon negative” plan, not a carbon neutral one. Second, the implication is that population can continue its unhindered growth—as if a world of 10 billion “carbon neutral” people could be sustainable. It can’t. But this raises an important question: How many people can the planet sustain? We can do a quick analysis, comparable to what I have done above. The total usable land area on Earth is around 11.2 billion ha. If we set aside half (5.6 bha) for nature and live on the other half, and we assume the current global average footprint of 2.8 ha/person, then the planet can support just (5.6 / 2.8 =) 2 billion people at current living standards. This is a decline of 74% from the current 7.7 billion… Obviously, we could sustain a higher population if we reduced the global average footprint. Theoretically, 5 billion people are sustainable if they all live at the poverty level of 1.0 ha/person. But that’s not a viable goal” (David Skrbina, “The population question: Toward a plan for global sustainability”, The Overpopulation Project”, 13 January 2020: https://overpopulation-project.com/the-population-question-toward-a-plan-for-global-sustainability/ ).