[petree]

It can't scale up if it still needs to be produced in the same quantities. It takes a lot of farmland, about 80% in fact, to produce feed for livestock (especially for cattle) even with calorie-dense feed like cereals. You'd have to cut down a lot of forest to make pastures.

[cwkoss]

Permaculture techniques can often support significantly greater density than monoculture, but are often not conducive to machine harvest, so end up being much more labor intensive