Kill the Wolves, Kill the Rivers

Yank all the starfish off a sea stack in coastal Washington, and within months the mussels that the starfish would normally eat form a diversity-crushing monopoly. Take sea otters out of the ocean around an Aleutian island, and the sea urchins the otters would normally eat mow nearby kelp forests into oblivion. Remove cougars from the Eastern Seaboard, and white-tailed deer lay waste to forests. Take wolves out of Yellowstone, and elk decimate the cottonwood, willow, and aspen seedlings. From The Boston Globe