You picked up one of my pet peeves.
Millions of buffalo were destroyed - that was a poor and short sighted decision. However, it happened.
If you want the prairie type habitat to remain viable for everything from antelope to mice, the buffalo need replacing. They did everything from toughening the roots of the ground cover (thus maintaining the fairly thin soil), to fertilizing, to keeping watering holes open. Cattle do the same job quite nicely.
I was working on a wellsite in the early '90s, down near Glenrock, Wyoming, and decided to take a few minutes of off time and hike up on the ridge west of the drilling rig. As I got up to the top I could see the rig on one side, the access road running down the other side of the ridge until it came to a gap, where it crossed the ridge line and proceeded to the well pad. I was knocking around, looking to see what I could find (fossils, minerals, artifacts, whatever there was to see) and heard vehicles approaching on the lease road. Three black suburbans in convoy went past (down the hill from me) at a high rate of speed, pulled onto the well site like a swat team, the doors flew open and people scattered from the vehicles with clipboards in hand. It looked like a raid.
Me?
I just decided since it was my off time, I'd just stay where I was and observe. No sense walking into that, it just had a bad vibe.
After about an hour of them climbing all over everything looking at and under stuff, the herd marched off to the Company Hand's shack with a couple going in and the rest milling around the outside. When the two who went in came out, they climbed back in the vehicles and left, in convoy again, down the lease road in a cloud of dust. Only then did I come back off the ridge to see what had been going on. It was a BLM inspection, looking for violations. I was told if they had caught one of the hands taking a leak on the edge of the location it would have been a Felony, punishable by a $10,000 fine and possible jail time. Whoa. As if those herds of buffalo, from horizon to horizon, that took three days to pass just held it and never urinated...
I knew then we were facing an unrealistic interpretation of the ecosystem. It has only gotten worse.