Beavers, in some sense, must, because their impacts have had plenty of time to get back at the beavers if it was going to. That doesn't mean they didn't ruin it

Beavers, in some sense, must, because their impacts have had plenty of time to get back at the beavers if it was going to. That doesn't mean they didn't ruin it for some other species. It's kind of the idea that the most successful parasites can't kill their hosts too efficiently or quickly, because then they run out of places to live. If you screw up your environment like that, it'll come back to haunt you.