Book excerpt: An unintended experiment teaches real-life lessons about life’s intricate interconnections. In the 1800s, the American government decided to eliminate threats to livestock near Yellowstone National Park. By 1926, there were no gray wolves left in the park. This set off a cascade of devastating changes to virtually every part of the park’s ecosystem, and the once-thriving landscape was soon in distress. Then, in an effort to reverse course, gray wolves were reintroduced in 1995. In time, animal populations start to stabilize, waterways are restored and, miraculously, health returns to the park. This remarkable story of transformation is sure to captivate, and to inspire respect for nature’s surprisingly complex balancing act.