According to their math humanity is currently using 1.5 earths.
I find that outcome suspect.
They're totally cooking the books on that. Counting CO2 emissions as taking up 2.5 of the 4 earths we'd "need"is just inflating the numbers to sell the idea that our only choice is to drastically cut our standard of living, because if you use the real figure (presuming that's not also screwed with), we need 1.5 earths, and everyone's response to that would be "eh, we can cut down a bit, and improve efficiency a bit, and we're fine".....which is not really in line with the DOOOOOOM agenda of most greens.