Those localized plants are usually hardy perennials that don't require a plow or herbicides or irrigation or fertilizers or humans holding their little hands so they can survive. They are adapted to the local conditions, and are more efficient at using those local conditions to their advantages.
grains are far from the only alternative to native grasslands.
Emerson White wrote:
Conservation didn't begin until after agriculture and domestication
Stability and sustainability is about having the full suite of players in the system, not about having all vintage stock in it's original packaging.
we are not at peak population yet
Conservation didn't begin until after agriculture and domestication, because those freed up enough human capital to be able to protect valuable lands and ecosystems. Before that it was one ecological disaster after another as man stretched out over the globe.
If you want a really good example of permaculture on the large scale, check out the civilizations of Brazil. They literally made the Amazon forest what it is today, mostly from cultivating their forest garden agriculture model. They didn't destroy their ecosystem, and in fact, they may have had a hand in creating one of the most diverse biological areas on the planet.
There was a wave of extinction of Megafauna as humans colonized
In EVERY case, the cultivated plants produce more than the wild ones
All of them were grown sustainably
To use the Brazilian Culture as an example denies any effort by the forest experts in plant and habitat improvement
This theory doesn't match the evidence. Several major South American civilizations predate the mass extinction by at least 10,000 years. And it wasn't just megafuana, it also includes tons of species of insects, birds, reptiles, amphibians, and other non-food microfauna. So, the modern perspective is that it was not necessarily a human-cased extinction.