The ecological footprint is a measure of human demand on the Earth's ecosystems. It is a standardized measure of demand for natural capital that may be contrasted with the planet's ecological capacity to regenerate. It represents the amount of biologically productive land and sea area necessary to supply the resources a human population consumes, and to assimilate associated waste. Using this assessment, it is possible to estimate how much of the Earth (or how many planet Earths) it would take to support humanity if everybody followed a given lifestyle. For 2007, humanity's total ecological footprint was estimated at 1.5 planet Earths; that is, humanity uses ecological services 1.5 times as quickly as Earth can renew them. Every year, this number is recalculated to incorporate the three-year lag due to the time it takes for the UN to collect and publish statistics and relevant research.

Although the term ecological footprint is widely used and well known, the methods used to calculate it vary greatly. However, standards are now emerging to make results more comparable and consistent.

Mathis Wackernagel is a Swiss-born sustainability advocate. He is currently President of Global Footprint Network, an international sustainability think tank with a presence in Oakland, California; Brussels, Belgium, and Zurich, Switzerland. The think-tank is a non-profit that focuses on developing and promoting metrics for sustainability.

After earning a degree in mechanical engineering from the Swiss Federal Institute of Technology, he completed his Ph.D. in community and regional planning at the University of British Columbia in Vancouver, Canada in 1994. There, as his doctoral dissertation under Professor William Rees, he created with Professor Rees the ecological footprint concept and developed the methodology. He has worked on sustainability issues for organizations in Europe, Latin America, North America, Asia and Australia. Wackernagel previously served as the director of the Sustainability Program at Redefining Progress in Oakland, California (1999 - 2003), and directed the Centre for Sustainability Studies / Centro de Estudios para la Sustentabilidad in Mexico (1995-2001). In 2004, he was also an adjunct faculty at SAGE of the University of Wisconsin–Madison. In 2010, he was appointed Frank H. T. Rhodes Class of 1956 Visiting Professor at Cornell University (1 July 2011 – 30 June 2013).

Glenn Edward Lee Beck (born February 10, 1964) is an American conservative radio host, vlogger, author, entrepreneur, political commentator and former television host. He hosts the Glenn Beck Program, a nationally syndicated talk-radio show that airs throughout the United States on Premiere Radio Networks. He formerly hosted the Glenn Beck television program, which ran from January 2006 to October 2008 on HLN and from January 2009 to June 2011 on the Fox News Channel. Beck has authored six New York Times–bestselling books. Beck is the founder and CEO of Mercury Radio Arts, a multimedia production company through which he produces content for radio, television, publishing, the stage, and the Internet. It was announced on April 6, 2011, that Beck would "transition off of his daily program" on Fox News later in the year but would team with Fox to "produce a slate of projects for FOX News Channel and FOX News' digital properties". Beck's last daily show on the network was June 30, 2011. In 2012, The Hollywood Reporter named Beck on its Digital Power Fifty list.

Albert Arnold "Al" Gore, Jr. (born March 31, 1948) served as the 45th Vice President of the United States (1993–2001), under President Bill Clinton. He was the Democratic Party's nominee for President and won the popular vote in the 2000 U.S. presidential election.

Gore is currently an author and environmental activist. He has founded a number of non-profit organizations, including the Alliance for Climate Protection, and has received a Nobel Peace Prize for his work in climate change activism.

Gore was previously an elected official for 24 years, representing Tennessee in the U.S. House of Representatives (1977–85), and later in the U.S. Senate (1985–93), and finally becoming Vice President in 1993. In the 2000 presidential election, Gore won the popular vote by a margin of more than 500,000 votes. However, he ultimately lost the Electoral College to Republican George W. Bush when the U.S. Supreme Court settled the legal controversy over the Florida vote recount by ruling 5-4 in favor of Bush. It was the only time in history that the Supreme Court has determined the outcome of a presidential election.