Global urban structural growth shows a profound shift from spreading out to building up

Abstract

We present a new study examining the dynamics of global urban building growth rates over the past three decades. By combining datasets for 1,550+ cities from several space-borne sensors—data from three scatterometers and settlement-built fraction based on Landsat-derived data—we find profound shifts in how cities expanded from the 1990s to the 2010s. Cities had both increasing building fractional cover and increasing microwave backscatter (correlating with building volume), but over the three decades, growth rates in building fraction decreased in most regions and large cities, while growth rates in backscatter increased in essentially all regions and cities. The divergence in rates of increase of these metrics indicates a shift from lateral urban expansion to more vertical urban development. This transition has happened in different decades and to different extents across the world’s cities. Growth rate increases were largest in Asian cities. This shift toward vertical development has profound consequences for material and energy use, local climate and urban living. The changing built structure of cities reflects and affects social and environmental forces. Combining remotely sensed and other data, this study finds a global shift in the past three decades, with cities growing more vertically than horizontally.