For years, planners and others have raised concerns about the amount of land that urbanization occupies, especially in the United States and other developed nations. My attention was recently drawn to an estimate that 2.7% of the world’s land (excluding Antarctica) is occupied by urban development. This estimate, which is perhaps the first of its kind in the world, is the product of the Columbia University Socioeconomic Data and Applications Center Gridded Population of the World and the Global Rural-Urban Mapping Project (GRUMP) and would amount to 3.5 million square kilometers.
While the scholars of Columbia are to be complimented for their ground breaking work, their estimate seems very high, especially in light of the fact that in the United States, with the world’s lowest density urban areas, only 2.6% of land is urbanized. Further, the data developed for ourDemographia World Urban Areas and Population Projections would seem to suggest a significant overstatement of urbanization’s extent. Demographia World Urban Areas and Population Projections data are generally from national census authorities and examination of satellite photography.