Cities are often described as having a heartbeat or pulse, but what does this metaphorical term actually mean? According to a new study 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 and analyzed. This concept is not just a figurative expression; it’s a tangible representation of the complex processes that shape urban development.
The authors of the paper, led by Zhe Zhu from the University of Connecticut, adopted a broad definition of urbanization that encompasses six key dimensions: demography, economy, infrastructure, environment, governance, and culture. This framework allows researchers to capture the dynamic nature of cities as living, adaptive ecosystems rather than static grids.
Traditionally, urbanization has been measured through outcome-based metrics such as population growth or GDP expansion. However, this approach only provides a snapshot of the city’s development without revealing the underlying dynamics. The new study aims to fill this knowledge gap by analyzing data from various sources, including satellite imagery and geolocated mobile or social media data.
The researchers focused on six cities: Seattle, Shenzhen, Lagos, Mumbai, Dubai, and Mexico City. They analyzed data from the NASA Harmonized Landsat and Sentinel-2 databases to examine new construction, repairs, improvements to infrastructure, green space expansions, and demolitions. The results revealed three distinctive vital signs that characterize urban metabolic activity:
Spiky Urbanization
Urbanization is not a smooth continuous process but rather characterized by sharp, short-lived spikes in activity. Dubai’s coastal areas provide an exemplary case of this phenomenon, with large spikes in redevelopment activity driven by capital-intensive projects like luxury towers or mixed-use buildings. In contrast, Shenzhen’s spikes are more clustered and reflect the city’s capacity for rapid mobilization of capital and construction.
Cyclical Urbanization
Urban development is cyclical and non-periodic, featuring distinct phases of building/expansion, a peak, and stabilization followed by relative decline or dormancy. Each city exhibits unique patterns that cannot be predicted like temporal seasons. For instance, Lagos has fragmented and uneven cycles with some neighborhoods experiencing prolonged lulls punctuated by occasional periods of heightened activity.
Asynchronous Urbanization
Even within cities, there is substantial variance among neighborhoods, making the urbanization process asynchronous. This means that different areas may exhibit their own rhythms, and a major spike in activity in one region does not necessarily indicate the same pattern elsewhere. The COVID-19 pandemic provided a notable exception, with synchronized dips in activity worldwide – akin to cardiac arrest.
The study’s findings suggest that urbanization is a mosaic process produced through overlapping but uncoordinated pulses of activity that vary across space and time. This ‘urban arrhythmia’ may not be a sign of failure but rather an adaptive mechanism that distributes urban stress over time, avoiding overheating, labor shortages, and infrastructure collapse associated with total synchronization.
By understanding the patterns of urban metabolic activity, researchers can provide valuable insights for informed public policy decisions. This new perspective on cities as living systems has significant implications for urban planning, development, and governance.
Source: Original article