Predator-prey relationships are strong evolutionary drivers and prime movers and shapers of our natural world. They also make for dramatic stories that seem to portray black-and-white cases of cause and effect. Ecosystems, however, function at such a high level of complexity that seldom are things as straightforward as they appear.

In Yellowstone, introduced wolves take down elk and the park’s forests grow and streams revert to meandering courses. In the Salish Sea, seals and sea lions are protected and salmon populations crash. Along the Pacific flyway, we stop poisoning and shooting bald eagles and suddenly seabirds are struggling.