Ripple and Beschta base their conclusions on theory about feeding relationships between species, browsers' risk of predation since the reintroduction of wolves into the park in 1995, and empirical research. In the view of Ripple and Beschta, extirpation of wolves in the early 20th century was "most likely the overriding cause of the precipitous decline and cessation in the recruitment of aspen, cottonwood and willow across the nothern range."
The new theory thus brings a significant new factor into long-running, intense debates over the proper management of Yellowstone. Ripple and Beschta conclude that, for Yellowstone, "restoration goals should focus on the recovery of natural processes." The identified fear factor might also be important in other regions, although the evidence is less well developed. Journalists may obtain copies of the article by contacting Donna Royston, AIBS communications representative.