Data were collected which explain several factors that modulate resource limitation and predation in Yellowstone National Park's system, determining when and where predators or resources will dominate in regulating populations. The effects of increasing large mammalian herbivore populations, unchecked by natural predators, on ecosystem processes are profound, and cascade through all trophic levels. Research suggests wolf predation regulates elk populations and thereby protects primary producers from destructive grazing. Elk foraging intensity measurements, aspen regeneration dynamics, and the regulatory role of beaver in both terrestrial and aquatic systems were examined.
Research infers the existence of a wolf-induced trophic cascade.
Although biological systems are transient and subject to change over time, research provides evidence of top-down trophic regulation in Yellowstone's ecosystem at this time.