OK, now raise the global standard of living to that of the US and Western Europe. Feel free to reduce the earths population by 1/4 since a coming decline (in half a century or so) is claimed.

Now, take most of the water out of the aquifers and deplete most of the easily accessible minerals and oil. Drop a bunch of them in the ocean if you want. Kill off a large number of fish.

See the problem? Even at current population levels, with rising living standards and diminishing resources it is unsustainable.