William J. Ripple is a professor of ecology at Oregon State University in the Department of Forest Ecosystems and Society. He is best known for his research on terrestrial trophic cascades, particularly the role of the gray wolf (Canis lupus) in North America as an apex predator and a keystone species that shapes food webs and landscape structures via “top-down” pressures. Ripple heads the Trophic Cascades Program at Oregon State University, which carries out several research initiatives such as the Aspen Project, the Wolves in Nature Project, and the Range Contractions Project. He has a Ph.D. from Oregon State UniversityRipple was the lead author on the "Global Scientists' Warning to Humanity: A second Notice", published on November 13, 2017. This article includes 15,364 scientist co-signatories from 184 countries. The article suggests "To prevent widespread misery and catastrophic biodiversity loss, humanity must practice a more environmentally sustainable alternative to business as usual." In 2020, Ripple led The World Scientists' Warning of a Climate Emergency, declaring with more than 11,000 scientist co-signatories from 153 countries that "Planet Earth is facing a climate emergency" and presenting six steps for avoiding the worst effects of climate change. Subsequently, Ripple has led an annual "World Scientists' Warning of a Climate Emergency" series of reports.In addition to being a highly cited researcher, Ripple is the director of the Alliance of World Scientists, an independent organization with more than 25,000 scientist members that acts as a "collective international voice of many scientists regarding global climate and environmental trends."Ripple's work on environmental issues was highlighted in The Scientists' Warning—a documentary film about a researcher who started a movement to encourage scientists to help turn scientific knowledge into action. Source: Wikipedia (en)