There are quite a few who argue that we are already overshooting the carrying capacity. One way to measure it is the global acre http://en.wikipedia.org/wiki/Global_hectare

And according to the footprintnetwork we are already using up 150% of earths carrying capacity: http://www.footprintnetwork.org/en/index.php/GFN/page/basics_introduction/ thus using up the available resources faster than the are (re)generated.