People often speak metaphorically of the heartbeat or pulse of a city, but according to the authors of a new paper published in the Proceedings of the National Academy of Sciences, cities do indeed have an “urban pulse”—an indication of urban “metabolic activity” that can be measured to suss out telltale patterns. And those patterns could help inform future public policy around urban planning.
The precise definition of urbanization has shifted over the centuries. Zhe Zhu of the University of Connecticut and his fellow authors adopted a broad version for their study. It features fundamental “processes of concurrent change in at least six dimensions, including demography, economy, infrastructure, environment, governance and culture,” they wrote. “Together they give rise to outcomes, measurable results of the process, such as population growth, urban land expansion, GDP growth, and innovation.” Their chosen metrics reflect this dynamic view: Cities are not static grids but “living, adaptive ecosystems.”
“For decades, we had just been capturing the outcome of urbanization—a house that’s been built, or a road expansion,” said Zhu. “But you don’t really see the dynamics within an urban area. This is going to be a very impactful tool influencing not only top-down policy decisions from governments but also bottom-up decisions from everyday people navigating their cities.” One day we may be able to check a neighborhood’s “urban pulse” while house-hunting, for instance, or while scouting potential locations for a new business.
Thanks to advances in remote sensing and various analytical methods, it’s possible to gather multidimensional data from a variety of sources, such as satellite imagery, or geolocated mobile or social media data. Zhu et al. got their data from the NASA Harmonized Landsat and Sentinel-2 databases to analyze new construction, repairs, improvements to infrastructure, green space expansions, and demolitions in six different cities: Seattle, Shenzhen, Lagos, Mumbai, Dubai, and Mexico City.
Three key vital signs
Their analysis revealed three distinctive “vital signs” for monitoring cities. First, urbanization is “spiky”: There are sharp, short-lived spikes in activity, not smooth continuous growth. The best example of this, per the authors, is Dubai, whose coastal areas showed very large spikes in redevelopment activity—most notably capital-intensive projects like luxury towers or mixed-used buildings. Shenzhen’s spikes, by contrast, were more clustered, “reflecting the city’s capacity for rapid, state-led mobilization of capital and construction,” they wrote.
