Nobody knows what its capable of sustaining. There's stuff like using resources more efficiently, recycling etc. We aren't good at these things yet, consumption could go a lot higher with improvements to those.
> We aren't good at these things yet, consumption could go a lot higher with improvements to those.
That's an Malthusianism[0] right here. Why recycling and increased efficiency themselves aren't a solution? Because people will increase their consumption to offset all the gains.
C.f.:
"Why are even some affluent parts of the world running out of fresh water? Because if they weren’t, they’d keep watering their lawns until they were."
It's a complete speculation, because I can't cite this, but isn't Earth not capable of sustaining 7+ billion people? Exponential population growth brings even greater exponential rise of greenhouse effect, oil consumption, deforestation, etc. IMHO it is the main problem of overpopulation.