Beyond 2D land consumption: A scaling-law framework for evaluating 3D urban space consumption and population dynamics in fifteen East Asian megacities

As cities expand both outward and upward, assessing global urbanization requires a three-dimensional perspective that captures the complete picture of urban growth. However, conventional land-consumption metrics fail to capture vertical intensification, while large-scale building-volume data that are consistent across years in data source, method, resolution, and precision remain difficult to obtain. To address this gap, this study asks whether population potential, inferred from remotely sensed physical environments, can serve as a scalable proxy for building volume and reveal urban expansion patterns that remain hidden in 2D assessments. Using fifteen East Asian megacity regions as a comparative sample, we integrate gridded population potential, land consumption rate, height change rate, space consumption rate, and district-level development indicators within an urban scaling framework. The results show that population potential explains building volume more effectively than population count, increasing the mean R 2 of the scaling model from 0.4891 to 0.6432 when using population potential. Development-mode analysis further reveals scale-dependent patterns: across megacity regions, vertical growth differentiates national urban systems more clearly than horizontal expansion, whereas within megacity regions, more developed districts generally expand less horizontally and often grow more vertically. Finally, the comparison between LCRPGR and SCRPGR shows that many districts appearing coordinated under the 2D land-consumption assessment still exhibit rapid volumetric growth relative to population growth. These findings suggest that population potential and volumetric diagnostics can complement conventional SDG 11.3.1 indicators by revealing dimensions of urban expansion that are overlooked in two-dimensional land-use assessment.