Four ways to build heat-resilient cities

ByMaia Rosenfeld and Maggie Green
Wednesday, August 16, 2023
Children attempt to cool off in a water fountain in Grand Park in downtown Los Angeles in July.

As cities prepare for the effects of extreme heat as a result of climate change, experts recommend focusing on greener cities and paying greater attention to vulnerable populations. While there is no one-size-fits all approach to mitigating extreme heat, even slight adjustments to building infrastructure could reduce cooling costs, and better messaging could result in fewer heat-related deaths.

1. Constructing rooftop gardens and local parks

"We have to be thinking about the cool surfaces, the cool roofs and streets," said Dr. John Balbus, Acting Director of the Department of Health and Human Services' new Office of Climate Change and Health Equity. "We have to be thinking about the tree planting and the green spaces that can help provide some respite from hot indoor environments."

See more from our Weathering Tomorrow series

Many urban buildings are implementing rooftop gardens, which help absorb carbon dioxide and cool the air nearby. Cold air falls, reducing street-level temperatures.

"Green roofs, while they're higher up, the cool air tends to go down," said Dr. Vivek Shandas, a professor at Portland State University. "Depending on what's on the green roof, and the extent of greening on that roof, we can get a little bit of cooling. Maybe not as much as a street tree or a park, but a little bit of additional cooling on the sidewalks and areas surrounding that building."

Peter Elwin, Head of Food and Land Use for environmental think tank Planet Tracker, studies the effects of extreme heat on urban environments. He added that small local parks can offset some of the negative heat effects of urban heat islands - areas with lots of asphalt, concrete and tall buildings and few green spaces. Urban heat islands can be as many as 18 degrees hotter than areas with trees or a bit of water, Elwin said.

"So in that particular urban space, literally one block, you can find people getting really ill, the factory has to shut, the office has to close, because the air conditioning can't actually cope with that level of heat," he said. "Two blocks down the road, there's another company which happens to have a few trees outside, a bit less asphalt and concrete. They're fine."

2. Emphasizing urban forestry

Shandas studies the phenomenon of urban heat islands. He says many of these areas are in low-income communities of color, often part of historically redlined neighborhoods.

"Those historically segregated neighborhoods have orders of magnitude less tree canopy than their invested-in and green-lined counterparts, and that legacy casts a long shadow," Shandas said.

He added that the benefits of trees are proportionally related to the amount of space taken up by the surrounding built environment.

"If we have a lot of, for example, big box stores, asphalt, parking lots, buildings that are really large, they tend to absorb a lot of the sun's radiation and re-emit it out, and putting a few trees in there won't really do much," Shandas said. "If we're talking about one acre, for example, of built environment where we have asphalt, we really need almost double that of trees to be able to cool that environment."

Additionally, some buildings set up "green walls," entire sides covered in vines or shrubbery. Shandas said one green wall can decrease the surface temperature of a building by up to 50 degrees.

On the city level, establishing an urban forestry division is a huge step in reducing heat risk, Shandas added.

"When we do have a dedicated entity that is responsible for administering and coordinating all the urban forestry issues, we see much better kinds of outcomes in terms of urban forests," he said. "It's not just, you know, putting a lot of trees down, I really start looking at the conditions in which these tree planting and greening operations are happening."

While a lack of preparation could spell doom for cities likely to see increasing temperatures in the next 30 years, taking action now and setting up urban forestry and environmental impact agencies within local governments could ameliorate some of the effects of extreme heat before it's too late.

"Let's just think about making our cities and our towns more resilient by planting trees, by creating green spaces," Elwin said. "So actually, doing the opposite of the Joni Mitchel song and sort of, you know, tearing up a parking lot, making a bit of paradise, because it's actually helping climate resilience."

3. Improving public health messaging and health system readiness

Public health messaging and communication around heat risks are critical to withstanding heat waves, said Dr. Cecilia Sorensen, director of Columbia University's Global Consortium on Climate and Health Education and an associate professor at Columbia's Medical Center and School of Public Health. This requires careful framing and timing, she noted, both through public alerts and from clinicians to their patients.

When prescribing medications that cause heat sensitivity, Sorensen said, doctors should warn their patients: "It's really hot out and you're on medications that are going to affect your ability to cool yourself, and here's what you can do, here are the signs and symptoms."

Sorensen added that health systems need to institute triage protocols for extreme heat, systems for rapid cooling, and a "wraparound approach to patients who have fallen through the cracks of all our preventative stuff."

Health systems themselves need to be prepared to endure longer and more frequent heat waves, Balbus added.

"If the community health center or the emergency room in a low-income community goes down in a heatwave, people are going to die, people are going to suffer," he said. "So we're working on the resilience of the health system."

HHS is also creating a new toolkit for doctors and nurses or social workers in a clinic to help connect vulnerable patients with resources to beat the heat - a "one stop shop" for accessing assistance through Medicare, Medicaid and other federal agencies.

4. Understanding where vulnerable populations live

To Sorensen, building climate resilience starts with vulnerability mapping: "identifying these pockets where you have overlapping vulnerable populations, so, high percentages of elderly patients or patients who have chronic comorbidities, with, for example, urban heat islands."

Once these neighborhoods have been identified, the next step is determining which interventions to employ there, Sorensen added.

"Oftentimes, this involves asking community members what would be helpful," she said. "Do you want more trees? Do you want public water fountains?"

Houston, Texas, has done this kind of mapping, identifying the urban heat islands that lie primarily in low-income areas and communities of color.

"These marginalized communities are in a constant state of need and recovery," said Houston Mayor Sylvester Turner. "And that's where we really need to target our resilience efforts when we're dealing with these extreme weather events."

Ultimately, Turner and Sorensen agreed, climate resilience will depend on bridging the gross inequities that put some groups at higher risk.

"I see a heat-resilient community as a community where everybody has equal access to clean air and a healthy environment. No matter where you sit on the economic spectrum, you live in safe housing that is able to be cooled and heated, and you have access to green spaces," Sorensen said. "You shouldn't have to pay a premium for this, this should be a right to health issue."