This is absolutely fascinating and is an example of how man's interference in nature has had such a devastating effect that fortunately, has been remedied by a few. Maybe we have still time to learn.
"You can be young without money but you can't be old without money"
Maggie the Cat from "Cat on a Hot Tin Roof." by Tennessee Williams
I knew about the regrowth of forests when apex predators are reintroduced, and I knew that other animal species tend to flourish... I didn't know that rivers changed their courses.