How did did the riparian ecosystems thrive when there were tens of millions of bison? There is the same order of magnitude of cows in the US today (90 million) as bison hundreds of years ago (30-60 million.) Bison are also generally much heavier, meaning they eat more and trod the ground more deeply.
The historical range of the American bison was largely not overlapping with BLM grazing lands. The bison, a sensible animal, wasn't found in California, Nevada, Oregon, and Washington.
I think we are safe in describing the pre-columbian bison range as not marginal, and the post that started this thread is about how most of our cattle grazing is on marginal lands. The way Americans do this is the worst possible way: grow feed on the excellent grazing range, and feed it to an animal that spends most of its life either grazing a desert or standing in parking lot. We'd get more of everything, easier and cheaper, if we just grazed bison where we currently grow corn.
