Wolf reintroduction to Yellowstone National Park aimed to control elk populations and restore riparian vegetation, especially willows, by reducing browsing. A decade-long study tested this by manipulating browsing pressure and stream hydrology (simulating beaver dams) in four treatments: browsing excluded/stream dammed, browsing excluded/stream undammed, browsing allowed/stream dammed and browsing allowed/stream undammed (control). Results showed that browsing exclusion alone was insufficient for willow recovery to a sustainable height (>2 meters). Combined browsing exclusion and simulated beaver dams significantly increased willow growth, indicating both predator control and hydrology are essential. Without beavers, lowered water tables persisted, preventing willow recovery even with reduced browsing. Therefore, successful riparian restoration requires both managing predator-prey dynamics and addressing hydrological conditions, including the role of beavers. Holistic, integrated management approaches are crucial for achieving ecosystem recovery and avoiding persistent ecological imbalances.
