People often talk metaphorically about 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 actually have an “urban pulse”—a signal of urban “metabolic activity” that can be measured to understand telltale patterns. And those patterns could help inform future public policy around urban planning.
The exact definition of urbanization has changed over the centuries. Zhe Zhu of the University of Connecticut and his co-authors adopted a broader version for their study. It involves fundamental processes of concurrent change in at least six dimensions, including demography, economy, infrastructure, environment, governance and culture, he wrote. “Together they give rise to outcomes, the measurable results of the process, such as population growth, urban land expansion, GDP growth and innovation.” Their chosen metrics reflect this dynamic approach: cities are not static grids but “living, adaptive ecosystems”.
“For decades, we were just capturing the outcome of urbanization – a house that’s built, or a road extension,” Zhu said. “But you don’t really see the dynamics within the urban area. This is going to be a very impactful tool that will influence not only the top-down policy decisions of governments, but also the bottom-up decisions of everyday people living in their cities.” For example, one day we may be able to check the “urban pulse” of a neighborhood when looking for a home or potential locations for a new business.
Thanks to advances in remote sensing and various analytical methods, it is possible to gather multidimensional data from a variety of sources, such as satellite imagery, or geolocated mobile or social media data. Zhu et al. obtained their data from the NASA Harmonized Landsat and Sentinel-2 databases to analyze new construction, renovation, infrastructure improvements, green space expansion, and demolition in six different cities: Seattle, Shenzhen, Lagos, Mumbai, Dubai, and Mexico City.
three major vital signs
Their analysis revealed three specific “vital signs” for cities to monitor. First, urbanization is “spiky”: there are sharp, short-term booms in activity, not sustained growth. According to the authors, the best example of this is Dubai, whose coastal areas have seen a huge increase in redevelopment activity – particularly capital-intensive projects like luxury towers or mixed-use buildings. In contrast, Shenzhen’s spikes were more clustered, “reflecting the city’s capacity for rapid, state-led capital and construction,” they wrote.
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