The world is in the midst of a massive, unprecedented shift in population distribution towards urban centers. The United Nations Population Fund (UNFPA) reports that in 2008, for the first time there were more people living in cities than in the countryside1. Moreover, by 2030, it is estimated that five billion people will live in urban centers, with the predominant growth occurring in Africa and Asia. The newly published IPCC Report (Chapter 12) on Human Settlements, Infrastructure and Spatial Planning2 states that expansion of urban areas is on average twice as fast as urban population growth, and that the expected increase in urban land cover during the first three decades of the 21st Century will be greater than the cumulative urban expansion in all of human history.
