DURHAM, N.H. — In the past three decades, urban growth has shifted from an outward sprawl to an upward growth, particularly in large cities in Asia, according to new research by the University of New Hampshire. Their findings show that since the 1990s, this shift to more vertical architecture has been happening in relation to economic growth and can affect how residents live and get around, as well as impact the environment, local climate and energy use.

“Urban population has nearly doubled since 1990, with a need to increase transportation and infrastructure,” said Steve Frolking, professor emeritus of Earth sciences and lead author. “How cities grow affects their greenhouse gas emissions, demand for specialized materials and even impacts urban climates creating micro-climates — local atmospheric conditions that differ from those in the surrounding areas.”

In the first-of-its-kind study, published in Nature Cities, researchers analysed three decades of satellite data from around the world to characterize recent changes in urban growth. The data analysis, from the 1990s to the 2010s and more than 1550 cities, combined two types of satellite data: one that maps the footprint of cities from space in two dimensions and another that uses the reflections of beamed microwaves to characterize that footprint in three dimensions, allowing them to explore changes in the built environment.

The results showed that urban structural growth patterns across the world are evolving. In rapidly developing regions like Asia and Africa, cities transitioned from low-rise, outward growth buildings to more high-rise and upward growth architecture. Globally, the 2010s showed the largest area dominated by upward expansion (28%) compared to the 2000s (9%) or the 1990s (7%).

“Historically, large-scale high-rise development was mostly limited to a few megacities such as New York, Tokyo and Shanghai,” said Frolking. “However, we have observed a shifting trend toward upward building growth across many cities and regions.”

Researchers say that the shift in growth has important positive and negative implications in terms of future sustainability. For example, densely populated areas with taller buildings can help to preserve more land for nature and foster more walkable areas. However, construction of tall buildings can emit high levels of carbon, known as embodied carbon, as well as have higher energy needs. The scientists hope their findings will help further the understanding of urbanization and its impact on the Earth’s surface.

Funding for this study was provided by NASA, the European Space Agency and the Global Facility for Disaster Reduction and Recovery.

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