PIP: The ecological footprint of any specified population is defined as the total area of productive land and water required on a continuous basis to produce all the resources consumed, and to assimilate all the wastes produced by that population, wherever on Earth that land is located. Sample data show that as a result of enormous increases in per capita energy and material consumption, and growing dependencies on trade, the ecological locations of cities no longer coincide with their locations on the map. This finding indicates that no city or urban region can be sustainable on its own. However, it is noted that a prerequisite for sustainable cities is sustainability of the global hinterland. In closing such sustainability gap, the cities present both unique problems and opportunities, suggesting a much-improved accounting for the hidden ecological costs of urbanization and a redefinition of economic efficiency. Meanwhile, many of the environmental demands and impacts that can be traced to cities have nothing to do with the structure, form, or other inherent properties of cities. Rather, they are a reflection of societal and individual values and behavior. Hence, a major shift in values and consumption habits will be essential if human footprints are not to destroy the Earth's carrying capacity.