UW Researcher Studies How Urban Land Patterns Can Reduce Population Exposure to Climate Extremes

A University of Wyoming researcher was part of a recent study that investigated how changes in urban land and population will affect future populations’ exposure to weather extremes at the end of the 21st century.

Melissa Bukovsky, an associate professor in UW’s Haub School of Environment and Natural Resources, collaborated with Jing Gao, an assistant professor of geospatial data science at the University of Delaware, to look at urban areas -- including cities large and small -- across the continental United States, with various development densities and in different climate regions.

Intuitively, when an extreme weather event hits a city, the more residents a city has, the larger number of people are likely to be affected. Currently, 83 percent of the U.S. population lives in urban settings, according to the U.S. Census. This number is expected to grow over the coming decades, rendering urban climate resilience extraordinarily important. As a result, many people have the impression that the growing sizes of cities are making weather extremes worse for the people who live there.

However, cities are designed and built by people. So, it stands to reason that, if some methods of land development increase population exposures to extreme weather conditions, others might hold the potential to moderate or even reduce population exposures as the climate changes over the coming decades.

“This finding is counter to the common belief that population exposure to extreme events increases when urban land increases,” says Bukovsky, also a Derecho Professor in the UW School of Computing. “Our work suggests that development patterns may be identified that can reduce exposure, or at least not horribly amplify exposure to extreme weather events and, over the long term, these patterns could help guide development that is more resilient in the face of increasing instances of extreme weather.”  

Bukovsky was second author of a paper titled “Urban land patterns can moderate population exposures to climate extremes over the 21st century” that was published Oct. 26 in Nature Communications, an open-access, multidisciplinary journal dedicated to publishing high-quality research in all areas of the biological, health, physical, chemical, Earth, social, mathematical, applied and engineering sciences. 

Gao, who also is a resident faculty member in the Data Science Institute at the University of Delaware, was the paper’s lead author. During the study, which took place from late 2020 through August 2022, Bukovsky was a research scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colo.

The two used a data-driven model developed by Gao to predict -- based on development trends observed over the past 40 years -- how urban areas across the country will grow by 2100. The research team considered how these urban land changes might affect weather extremes, including heat waves, cold waves, heavy rainfall and severe thunderstorms. They then analyzed how many people would be exposed to these extremes under different climate and urban development conditions at the end of the century.

The research team’s computer simulations showed that, at the end of the 21st century, how a city is laid out or organized spatially -- often called an urban land pattern -- has the potential to reduce population exposures to future weather extremes, even for heat waves under very high urban expansion rates. Furthermore, how an urban landscape is designed -- meaning how buildings are clustered or dispersed and how they fit into the surrounding environment -- seems to matter more than simply the size of a city.

Even while climate change is increasing population exposures, the two found this applies to all cities -- from large metropolitan areas, such as New York City, to smaller towns in more rural contexts, such as Newark, Del.

“Regardless of the size of a city, well-planned urban land patterns can reduce population exposures to weather extremes,” Gao says. “In other words, cities, large and small, can reduce their risks caused by weather extremes by better arranging their land developments.”

“We have found that the spatial pattern of urban development on the landscape can moderate the exposure of people living in urban areas to extreme weather events, including extreme heat events,” Bukovsky adds.

The study’s findings differ from current common perceptions from existing research literature in this area that has almost exclusively focused on limiting the amount of urban land development.

In contrast, the new findings from this research encourage researchers and practitioners from a wide range of related fields to reconsider how cities are designed and built so that cities can be in harmony with their regional natural surroundings and more resilient to potential climate risks over the long run.

Gao likens the effects of climate change and urban land patterns on extreme weather risks to the effects of a person’s diet and activity level on their risk for health problems. Properly designed urban land patterns, she says, are like physical exercises that work to counteract poor dietary choices, contributing to a reduced risk for disease while helping a person become more fit in general.

“Carefully designed urban land patterns cannot completely erase increased population exposures to weather extremes resulting from climate change, but they can generate a meaningful reduction of the increase in risks,” Gao says.

The two are working to identify specific characteristics about the spatial arrangement of a city that can make it more -- or less -- resilient to future weather extremes. Identifying these patterns can help guide development that is more sustainable in the face of increasing instances of extreme weather. Through their efforts, Bukovsky and Gao hope to provide actionable suggestions for how to design and build urban areas that reduce their residents’ exposures to weather extremes in the long run.

Gao and Bukovsky emphasize that these characteristics will likely vary from region to region, now and as climate changes. For instance, what works in arid Phoenix, Ariz., will probably differ from what will work in humid New Orleans, La. Likewise, as climate conditions evolve, what might work today for a city could differ from what will work for that same city in the future.

Future research will look at mechanisms that drive climate change exposure reduction, according to the paper. These include both physical factors -- changes in evapotranspiration, albedo and sea breeze -- and population-land dynamics, including infill development and migration. 

“Eventually, we want our work to be directly useful to urban design and planning efforts, offering insights and tools for decision-makers to influence long-term social and environmental well-being at scale,” Bukovsky says. “First, though, we need to identify what development patterns can improve various cities’ long-term climate resilience. We will continue collaborating in the future.”

The current study was funded by the National Science Foundation, NCAR and the U.S. Department of Energy.