Bringing Back the Wolves: How a Predator Restored an Ecosystem

An unintended experiment in Yellowstone National Park, in which an ecosystem is devastated and then remarkably rehabilitated, provides crucial lessons about nature’s intricate balancing act.

In the 1800s, hunters were paid by the American government to eliminate threats to livestock on cattle ranches near Yellowstone National Park. They did such a good job that, by 1926, no gray wolf packs were left in the park. Over the following decades, virtually every other part of the park’s ecosystem w...