Early in this century, U.S. government agents trapped, poisoned, or shot every wolf they could track down in and around Yellowstone National Park. For thousands of years the wolf had been the preeminent predator of the vast wildlands of Greater Yellowstone, but by 1926 not one was left alive. In January of 1995, after a generation of struggle between the wolf's friends and foes, the wolf was returned to Yellowstone. Thomas McNamee chronicles the drama...

"In 1995, the gray wolf was reintroduced to Yellowstone National Park after a seventy-year absence. All these years later, we can clearly see the cascading effects this has had on the park's ecosystem. This is a spectacular example of a trophic cascade, the term used when an important member of an ecosystem goes missing and many other living things are indirectly affected, causing a chain reaction of events. In the case of the reintroduced wolves...