As president 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 commercial enterprise.

Denis was the principal national organizer of the first Earth Day in 1970 and took the event international in 1990. It is now the most-wide-observed secular holiday in the world. As board chair of the international Earth Day Network, Denis is gearing up for the 50th Earth Day anniversary in 2020. Over the years, 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 engineering and human biology at Stanford University; Regents’ Professor at the University of California; 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, and a Richard von Weizsäcker Fellow of the Bosch Foundation. During the Carter Administration, Hayes was the director of SERI — since renamed the National Renewable Energy Laboratory.

Hayes has received the national Jefferson Medal for Outstanding Public Service and the Rachel Carson Medal as well as the highest awards bestowed by the Sierra Club, the Humane Society of the United States, the National Wildlife Federation, the Natural Resources Council of America, the Global Environmental Facility, 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. Time magazine selected Hayes as one of its “Heroes of the Planet”. He has been profiled as “Newsmaker of the week” by ABC News and as “Today’s Person in the News” by the New York Times. Denis and his wife, 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).