Its not current population so much as the growth rate. China is 2/11 of the World. That's between 1/5 and 1/6, so small changes they make have dramatic effects decades down the road. Our current population is almost certainly not sustainable doing things the way we are now, but we are changing that. Population growth is only sustainable with dramatic changes in the way we live, yet we are adding people by the billion.
Its not current population so much as the growth rate. China is 2/11 of the World. That's between 1/5 and 1/6, so small changes they make have dramatic effects decades down the road. Our current population is almost certainly not sustainable doing things the way we are now, but we are changing that. Population growth is only sustainable with dramatic changes in the way we live, yet we are adding people by the billion.