An example of a trophic cascade is when Zebra mussels are brought into the Great Lakes,
where there is no natural predator, so the native
species numbers dwindle because the Zebra
mussels have no natural predators.
Wolves are taken out of Yellowstone and as a result,
deer numbers increase, tree nunbers decrease, and
river banks erode, causing the rivers to change
course.
There is not enough food for black bears to eat, so
they get into garbage and get sick.