BBC Online presents this six-part special on sustainable development. Created in anticipation of the now concluded Johannesburg Summit, this Web site provides a valuable resource for viewers wishing to learn more about sustainable development and related issues. The Web site consists of an overview and six sections: Population, Food, Cities, Waste, Tourism, and Energy. The sections offer an in-depth look at each topic and include audio clips of related interviews and news stories. The discussion forums are now closed, but visitors may read the occasionally insightful and often times heated comments that have already been posted. View the slide show to get a quick, visceral sense of human impact on the planet -- past, present, and future. Visitors may also take a quiz to calculate their ecological footprint, or how much of the earth's resources they individually consume each year.