Mapping Global 3D Building Density with the Global Building Atlas: Implications for Environmental Risk Hotspots

Environmental risk assessments require spatially explicit information on how people and assets are concentrated within the built environment. However, exposure metrics based solely on 2D building footprints or population grids fail to capture the vertical dimension that strongly influences heat exposure, air‑pollution accumulation, flood impacts, and infrastructure vulnerability. Leveraging the newly released Global Building Atlas (GBA)—a harmonized and globally consistent dataset of building footprints and height estimates, and currently the most comprehensive source of building information available—we introduce a global Building Density Index (BDI) that integrates key building parameters, including footprint area, building volume, height and distances, to quantify built‑up intensity as an indicator of environmental risk hotspots. The consistent global coverage of the GBA enables direct comparison of vertical density patterns across regions.

The BDI reveals pronounced regional contrasts in built‑volume concentration and illustrates how cities balance horizontal expansion, vertical growth, and the availability of land for settlement. Land-scarce regions, particularly in East and Southeast Asia, exhibit strong vertical densification, resulting in extremely high built volume concentrations even where horizontal extent is limited. In contrast, many rapidly expanding cities in Africa and South Asia primarily rely on horizontal expansion, consuming large areas of developable land while maintaining low vertical density. Latin American cities typically achieve high density through compact mid-rise forms, reflecting a distinct interplay between limited land availability and moderate vertical growth.

The BDI substantially improves the identification of zones where heat exposure, air‑pollution susceptibility, and built-up intensity combine to elevate environmental risks. By capturing the three-dimensional structure of the built environment, it offers a more realistic representation of how urban morphology amplifies or moderates these risks. As a globally consistent measure, the BDI provides a robust foundation for examining how land availability, horizontal expansion, and vertical growth interact to shape environmental vulnerability across diverse urban regions.