Population dispersion around cities as a driver of global urban land expansion
Abstract
Urbanization implies a massive expansion of built-up land globally. The magnitude of this phenomenon, however, largely depends on the degree to which growing urban populations spatially concentrate around existing settlements. Here we measure population centrality, or the inverse of residents’ average travel time to the urban core, in over 7000 urban areas worldwide between 2000 and 2020, and test its association with urban land expansion. We observe rising dispersion (i.e., lower centrality) in most urban areas everywhere except Europe and the Americas. This is concerning as the two variables are negatively related: all else being equal, each additional minute from the urban core comes with an extra 1.6 km 2 of built-up land. The association, however, is clearly negative only in small- to mid-sized and low- to mid-income urban areas, but poorly so otherwise. Moreover, higher centrality goes hand-in-hand with a modest containment of built-up land in Southeast Asia, Europe, Canada, and the USA, and an expansion of it in Eastern Asia and Oceania. Our findings suggest that increasing centrality may be a powerful tool for curbing urban land expansion in certain contexts, but an ineffective one in others, and that planning is needed to mitigate the spillovers of centralization.