Scientists have concluded that the Earth can sustain, at most, seven billion people at subsistence levels of consumption. Achieving "high life satisfaction" for everyone, however, would transgress the Earth's biophysical boundaries, leading to ecological collapse.

See the source article by following the link below:
Scientists have concluded that the Earth can sustain, at most, seven billion people at subsistence levels of consumption. Achieving "high life satisfaction" for everyone, however, would transgress the Earth's biophysical boundaries, leading to ecological collapse.