When the wolves were reintroduced the elk and deer population went down which meant the willows started to re grow along with the grass.the coyotes had to watch there backs.more and more animals started to come eat/live the grass/willows and then even more came to eat them. The rivers became more straight and so fish and other animals like otters came to live there. An objection to my answer is that when the wolves got outside yellow stone they started to kill live stock which NO farmers liked.
My evidence was a youtube video called "How the wolves changed the rivers" I also used a Youtube yideo called "wolve reintruduction" and an artical atteched to "How the wolves changed the rivers"
"What happend is that the presence of wolves triggered a still-unfolding cascade effect among animals and plants-one that will take decades of research to understand.
“It is like kicking a pebble down a mountain slope where conditions were just right that a falling pebble could trigger an avalanche of change. -Doug