As CEO of the Bullitt Foundation, Denis leads an effort to mold the major cities of Pacific Northwest and British Columbia into models of sustainability for a rapidly urbanizing planet. The Foundation applies ecological principles to the design of healthy, resilient human ecosystems. Under his leadership, the Foundation designed and constructed the Bullitt Center—the world’s greenest office building—which it operates as a successful commercial enterprise.

Denis was the principal national organizer of the first Earth Day in 1970, and he took the event international in 1990. It is now the most-widely-observed secular holiday in the world. He is now board chair emeritus of the international Earth Day Network. During the Carter Administration, Hayes was the director of the federal Solar Energy Research Institute — since renamed the National Renewable Energy Laboratory. Over his career, Hayes has been special assistant to the Governor of Illinois for natural resources and the environment; senior fellow at the Worldwatch Institute; adjunct professor of energy engineering and human biology at Stanford University; Regents’ Professor of Natural Resources at the University of California at Santa Cruz; and a Silicon Valley lawyer at the Cooley firm. Denis has been a visiting scholar at the Woodrow Wilson International Center for Scholars in Washington, DC and at the Bellagio Center in Italy, as well as a Richard von Weizsäcker Fellow of the Bosch Foundation.

Hayes has received the national Jefferson Medal for Outstanding Public Service, the Ridenhour Courage Prize, an inaugural Green Swan Award, and the Rachel Carson Award as well as the highest awards bestowed by the Sierra Club, the Environmental Law Institute, the Humane Society of the United States, the National Wildlife Federation, the Natural Resources Council of America, the Global Environmental Facility of the United Nations, the Interfaith Center for Corporate Responsibility, the American Solar Energy Society, and the Commonwealth Club. He has served on dozens of governing boards, including those of Stanford University, the World Resources Institute, the Federation of American Scientists, the Energy Foundation, Children Now, the National Programming Council for Public Television, the American Solar Energy Society, Greenpeace, CERES, and the Environmental Grantmakers Association. In 1999, Time magazine selected Hayes as one of its “Heroes of the Planet.” Life magazine selected him in 1990 as a member of “The Life 100 Most Important Americans of the 20th Century.” He has been profiled as “Newsmaker of the week” by ABC News and by the New York Times. Denis wrote Rays of Hope: The Transition to a Post-Petroleum World (WW Norton, 1977) and, together with his spouse, Gail Boyer Hayes, co-authored COWED: The Hidden Impact of 93 Million Cows on America’s Health, Economy, Politics, Culture, and Environment (WW Norton, 2015).