If the practices can be sustained, then we've increased the carrying capacity. To revert to traditional practices could decrease it again. The bigger the difference between our population size and carrying capacity, the worse that ride down will be. Of course, how these practices can be made/kept sustainable is an issue.
I'd say that the sustainability of the practices is _the_ issue. Depleting groundwater, eroding topsoil, reducing crop genetic diversity, and changing the climate may all be reducing the long-term carrying capacity.
