Sounds obvious enough, the great western plains, the African Serengeti, the steps of eastern europe, all thrived, supporting a abundance of life for thousands of years on the recycling of the grass.

Absence the migratorial animals, the wrong kind of soil microbiology takes over. It's a fact often over looked, how the great plains and forest of the world managed so much better before the stewardship of industrialized agriculture.

Try that he may, man will never improve upon what god has already perfected.