Introduction The large ambitions of Agenda 21, the global manifesto adopted at the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janiero, are announced in the first words of the Preamble. ‘Humanity,’ it declares, ‘stands at a defining moment in history.’ As Tim Luke points out in Chapter 3, the document’s framers clearly hoped to turn the tide of human history with an internationally agreed-upon blueprint for attaining sustainable development in the twenty-first century.