https://www.yellowstonepark.com/things-to-do/wolf-reintroduction-changes-ecosystem https://www.yellowstonepark.com/things-to-do/wolf-reintroduc... The video ("

https://www.yellowstonepark.com/things-to-do/wolf-reintroduction-changes-ecosystem https://www.yellowstonepark.com/things-to-do/wolf-reintroduc... The video ("How Wolves Change Rivers") states that humans had previously failed to control the deer. You could pay more humans hundreds of millions of dollars a year to patrol every one of these areas. Or you could simply let the wolves do it.