That may be true for energy use and even land development for housing, but potable water and food production are not so clear cut.
And I suspect that wildlife and plant communities would disagree as well with this assumption that human population is not yet excessive.
actually, like energy - our methods of food production is archaic and unsustainable. i have read quite a few articles in science journals that claim the technology exists to feed the entire human population and then some if people switch to smarter farming practices. without going into it in depth - i see a parallels between an energy revolution and farming one. both industries have existing technologies that are not being embraced.
Smaller families via greater wealth (forgetting the current gross inequalities in wealth even within developed nations) takes generations to slow population growth. Do wildlife and wild places have that much time?
no. sadly, many of them don't. there is no saving the majority of whats left of Southeast Asia's forests. even with a global push for change, there is just enough time or forest to turn around the tide of destruction that is happening in places like borneo, sumatra and indochina.
my only hope is that enough small protected forest pockets survive, be them glorified zoos and in need on intensive management, that in 300 years when we have solved many of these problems, that that wild biodiversity is still there alive and "banked" to reclaim some of its former range.
but i sincerely think we will destroy virtually the whole lot before we try and turn back the clock.