IN SUMMARY, SUSTAINABLE DESIGN AND URBAN PLANNING IS NOT ONLY GOOD FOR THE ENVIRONMENT, BUT ALSO HAS A POSTIVE ECONOMIC COST-BENEFIT -- Non-sustainable development assumes that it is too expensive to factor in the impacts of development on the natural environment and the livability of the overall community. Experience in the development of new urbanism communities like Mariemont, Ohio, planned communities such as Reston, Virginia and the re-development of downtowns such as Portland, Oregon, however, demonstrate that property values increase when the natural environment and the quality of life of a community are protected. People and businesses eventually flee unsustainable communities for a better life elsewhere. Sustainable communities, however, retain their populations from one generation to another and from one economic period to another. Also, experience shows that ultimately unsustainable development costs more. Unsustainable buildings become outdated as energy costs rise while residents flee cities that have allowed sprawl and pollution overtake the human and natural environment. And eventually air pollution regulations might limit new development in regions that have allowed themselves to be dominated by sprawl while business and residents move to the suburbs or to other cities that do not have the costa and problems of urban regions that were not designed to be sustainable. Sustainable design and urban and regional planning is not only earth-friendly and helps to address global problems such as global warming and climate change, but it makes economic and social sense as well.