Paving the planet: impervious surface as proxy measure of the human ecological footprint

Fundamental questions regarding the human-environment-sustainability problematic remain contested. What are the relative roles of population, consumption, and technology with respect to sustainability? How can sustainability be measured? Numerous metrics have been developed to address these controversial questions including ideas of carrying capacity, environmental sustainability indices, and ecological footprints. This work explores the question: is pavement a proxy measure of human impact on the environment? We explore and evaluate the use of satellite derived density grids of constructed area (aka 'pavement' or 'impervious surface') in the calculation of national and subnational 'ecological footprints'. We generated a global constructed area density grid for the 2000-2001 period using satellite observed nighttime lights and a population count grid from the US Department of Energy. Satellite data inputs to the population product include MODIS landcover, SRTM topography and high-resolution imagery. Calibration of the global constructed area density product was derived from high-resolution aerial photographs. We demonstrate that a satellite derived constructed area per person index can serve as a proxy measure of ecological footprints at both the national and subnational level. This relatively simple and globally uniform measure of human impact on the environment correlates strongly with other more difficult to obtain measures.