Global Monitoring with the Atlas of Urban Expansion

United Nations Sustainable Development Goal 11, “Sustainable Cities and Communities,” makes information about cities’ areas, their populations, and their change over time, essential inputs to the goal’s reporting requirements. The key charge of indicator 11.3.1 is to measure change in land consumption per capita over time in cities, to understand whether it is increasing, decreasing, or stable. The Atlas of Urban Expansion applied remote sensing and spatial analysis techniques to summarize global change in land consumption per capita using a sample-based approach. It revealed that land consumption per capita significantly increased on average in cities over the 1990–2000 and 2000–2014 periods. A relatively new publicly available global dataset of built-up area and population, the Global Human Settlements Layer (GHSL), now allows for the study of all cities on earth. Accuracy assessments of the Atlas and GHSL land cover classifications revealed encouraging similarities in overall accuracy but differences in each dataset’s ability to correctly identify the built-up and open space classes individually. Before adopting global grids to inform indicator 11.3.1, we must be able to explain anomalous population density values in over one-quarter of cities resulting from a first pass at automated global settlement mapping.