Perhaps I should remind you of a day, that comes once a year, called "Earth Overshoot Day". It is the day, when we used up more resources than the planet regenerates. The tendency for that day's date is come earlier each year.

The current population is not even sustainable. Half it and then perhaps it will be sustainable, if capped. Ecological damage will probably increase in the future, as swathes of people from developing countries will want to have the same living standards, that the first world countries experienced for decades. If you combine that with 11 billion people, it will be a disaster.