Vegetation and Population Density in Urban and Suburban Areas in the U.s.a

Reflectance characteristics of human settlements influence energy fluxes in the physical environment as well as our ability to monitor urban growth with satellite-based sensors. Spectral heterogeneity at the scales of 10 to 30 meters complicate the traditional land cover classifications derived from moderate resolution satellite imagery in urban and suburban areas. In this study we consider population density and vegetation abundance as the principal demographic and physical characteristics in urban and suburban areas of the U.S.A. We investigate their relationship in the cities of Atlanta, Chicago, Los Angeles, New York, Phoenix and Seattle and compare the results with the USGS National Land Cover Dataset’s urban classes. The multimodal population density distribution of the U.S.A. implies that it is possible to characterize suburban areas as those with population densities between 100 and 10,000 people/km, with rural areas at densities below 100 people/km and urban areas at densities above 10,000 people/km. We find that maximum vegetation fraction diminishes with increasing population density over the full range of densities, but the spectral heterogeneity at pixel scales still results in a wide range of vegetation fractions in demographically urban and suburban areas. The resolution difference between census units and the Landsat sensor’s field of view does not allow for a pixel scale spectral characterization of suburban land cover that is consistent with population density. A classification scheme based on spectral heterogeneity at multiple pixel scales, supplemented by auxiliary data sources, may provide a more accurate way to analyze urban growth.