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Heat is on for urban planners

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As temperatures rise, cities aim to transform heat islands and protect their citizens

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It’s noon in mid-August and the Houston heat is creeping into triple digits. Again. Coupled with the humidity of a steam bath, it’s enough to make eyeglasses fog, airways constrict, and skin sizzle in the direct sun.

All across town the heat — extreme even by Texas standards — has been unbearable for most of the summer. But in some parts of the city, it’s even worse. The sprawling urban core, crosshatched by massive freeways, punctuated with skyscrapers, and roaring with never-ceasing construction, suffers from something called the urban heat island effect. All of that concrete, pavement, steel, and glass — everything that makes a city a city — absorbs the sun’s heat throughout the day and then radiates it back into the air. In these hottest “islands,” temperatures can be 15 to 20 degrees Fahrenheit warmer than the grassy, leafy suburbs. That’s the difference between a sweltering 105 in a mall parking lot and a relatively pleasant 85 degrees on a tree-lined street elsewhere in the same metro area.

In Ed Pettitt’s neighborhood, the Third Ward, the heat island effect is palpable. Pettitt, who is president of the Rotary Club of Houston Skyline, could close his eyes and tell you where he is in the neighborhood based on temperature. Where developers recently knocked down a bunch of old trees, it’s scorching. “We’re being cooked,” he says. A couple of blocks away, dead tree branches and roots pepper another lot being cleared for development, the name of the street — Live Oak Street — an ironic punchline. The road is a stark contrast to the surrounding streets, where Pettitt and his longtime neighbors live in compact, older bungalows and narrow shotgun-style homes shaded by massive oak trees.

Ed Pettitt, president of the Rotary Club of Houston Skyline and a doctoral student in urban planning and environmental policy, is raising awareness and, through Rotary, working to address heat islands.

Among U.S. cities, Houston has the fourth most intense urban heat island effect, according to Climate Central, an independent research group. In a troubling dimension to the problem, the differences within cities, from hot to really hot, correlate strongly to income and race, with low-income communities of color often located in areas of cities with a lack of parks and an abundance of dense housing and polluting industries.

Pettitt, a graduate research assistant at the Bullard Center for Environmental and Climate Justice at Texas Southern University, has been educating people about heat islands and, through Rotary, working to try to bring down the temperature. “Houston’s heat problem is everyone’s problem,” says Pettitt. “By addressing urban heat islands, we’re taking a crucial step toward a cooler and more equitable future for our city.”

Last year shattered records: It was by far the planet’s hottest since modern data collection began in the mid-1800s — and probably the hottest in more than 100,000 years, judging by tree rings and ice core samples. The biggest factor driving up temperatures is the buildup of heat-trapping gases released by burning fossil fuels.

While many people dismiss heat as a nuisance, it’s the leading cause of weather-related deaths in the United States. High temperatures can trigger heat exhaustion and heatstroke. They can contribute to heart attacks and strokes and worsen other health conditions.

“It’s known as the silent killer because people don’t realize you can die from it. And it’s actually not that hard, to be blunt,” says Victoria Ludwig, a climate specialist with the U.S. Environmental Protection Agency’s Office of Community Revitalization.

The Gulfton neighborhood, which a 2020 study found was 17 degrees hotter than other parts of Houston.

In urban heat islands, those risks intersect with other vulnerabilities, especially in low-income areas. People may not be able to afford air conditioning. If they’re renters, their landlords may not be required to provide relief from the heat, or if they have asthma, poor air quality can trigger attacks and heat can exacerbate symptoms.

The heat has had health effects for Trinity Pasco-Stardust, a resident of Houston’s Third Ward. She has multiple sclerosis, and the heat worsens her symptoms, even causing her to have seizures. “This summer has been intense,” she says. In July and August, the triple-digit heat forced her to make choices every day that altered her plans. “I cannot go out,” she says.

For Pasco-Stardust, learning that she lives in an urban heat island — on top of life’s other challenges and injustices — was crushing. She says that much of her neighborhood is a food desert. There are no banks she can easily get to. And gentrification has driven up prices, making it hard to find a barber she can afford for herself and her three kids. “I always feel like we’re fighting to get something,” she says.

More and more cities are grappling with heat as an environmental justice issue, focusing efforts to lessen its effects in low-income communities of color. Cities around the world and in the U.S., like Phoenix, have even appointed chief heat officers. “We have mapped out our entire city, including heat islands, and it helps us make smart public infrastructure decisions,” explains Kate Gallego, the Phoenix mayor. Her city broke local heat records when temperatures topped 110 degrees for 31 days straight last year.

To cool the scalding streets, Phoenix has undertaken the country’s largest “cool pavement” program, which includes covering more than 100 miles of city streets in a light-colored sealant that reflects more sunlight and absorbs less heat, keeping surfaces 10 to 12 degrees cooler. Gallego says the city is also planting more trees, especially in lower-income neighborhoods and in areas with high foot traffic, such as around schools and libraries.

In Houston, too, for decades a center of the oil and gas industry, residents, the city government, and Rotary members are taking steps to address heat and climate resiliency.

Houston’s Third Ward is where Beyoncé grew up, and George Floyd, whose 2020 murder in police custody in Minneapolis sparked a social justice movement. It’s where, in the 1960s, a group of Black college students became a part of the Civil Rights Movement when they protested segregation at a lunch counter. It’s home to Emancipation Park, which formerly enslaved people purchased more than 150 years ago to celebrate their freedom, and also to Cuney Homes, Houston’s oldest public housing project.

Building lots where trees have been cleared for new home development in Houston’s Third Ward.

Pettitt moved to the area 13 years ago after returning to the U.S. from Botswana, where he served in the Peace Corps. He loved the neighborhood. But he also saw his neighbors’ struggles. About one-third of families live below the federal poverty level. On top of that, residents don’t have easy access to amenities taken for granted in wealthier neighborhoods, like sprawling shaded parks or healthy food.

Architect Donna Kacmar is designing sustainably built homes in Houston.

His first year living there, Pettitt enrolled in a graduate program at the University of Texas School of Public Health. “I realized that many of the public health challenges I saw were tied to inequities in the built and natural environments, such as limited access for residents to the city’s trails and greenways network,” he says.

It was around 2020 when Pettitt started paying close attention to the idea of heat islands. That was the year that a massive federal heat-mapping project led by the National Oceanic and Atmospheric Administration came to Houston. The citizen-science project, which has mapped dozens of U.S. cities, sent volunteers across 320 square miles on a hot August day to record temperatures. An area near the southwest neighborhood of Gulfton, which is dominated by large apartment complexes, hit 103.3 degrees, while a spot in Channelview, a modest suburb of single-family homes and numerous waterways, was a more manageable 86.2 — a staggering 17-degree difference.

Pettitt decided to pursue his PhD in urban planning and environmental policy, studying the effects of heat, green space, and energy equity issues.

When the Rotary International Convention came to Houston in June 2022, in the thick of summer, Pettitt and other local Rotary members saw an opportunity to share their work on the environment and heat. They offered attendees the opportunity to offset their carbon emissions from travel by donating money toward tree planting in an especially hot area of Houston’s Columbia Tap Trail, a former railroad route repurposed as a hike/bike trail in 2009.

They spoke to local TV reporters. And Pettitt spearheaded the design of a 3D heat model of Houston, constructed by nonprofit makerspace TXRX Labs and funded by Rotary clubs in District 5890 and the convention’s Host Organization Committee. Using overhead projection, colored lights were cast on 68 buildings and their surroundings, making it easy to distinguish hot spots from cooler areas. “Our mission extends beyond Houston’s borders,” Pettitt says. “We hope to encourage Rotary clubs everywhere to embrace environmental initiatives and prioritize the health of their communities.”

Ed Pettitt spearheaded the design of a 3D heat model of Houston that is now displayed at Houston’s Green Building Resource Center.

Houston’s Green Building Resource Center is tucked in a corner of the Houston Permitting Center, where builders and businesses must go for licenses and permits. The center feels like an interactive children’s museum, overflowing with attention-grabbing displays on water-efficient toilets, recycling facts, photos of low-water plants and drought-resistant trees, and options for design elements like recycled flooring and permeable pavers. “It’s like the Disneyland of innovative building technologies,” Pettitt says with a smile.

Steve Stelzer, program director at the Green Building Resource Center.

Although the center opened in 2009, Program Director Steve Stelzer says for years no one paid much attention to its work. Then, in 2017, Hurricane Harvey rolled into Houston and unleashed the worst flooding in the city’s history, with some parts of town deluged by more than 2 feet of rain in two days.

Then-Mayor Sylvester Turner launched climate resiliency plans spotlighting the need for Houston to address heat islands, including through tree planting, with a goal of 4.6 million new native trees by 2030, prioritizing underserved neighborhoods. The plans emphasize the need to protect vulnerable communities and call for light-colored and green roofs, lighter-colored pavement, and more vegetation, for starters.

Last July, the Green Building Resource Center added a new display: It’s now the permanent home for the heat island model that debuted at the Rotary Convention. The model is surrounded by signs about the causes of hot spots: areas with homogeneous building design, wide parking surfaces, little vegetation, and roads and highways.

And there are suggestions on how to establish cool corridors. “This is exactly what I want Rotary to do,” Pettitt says. He envisions the Columbia Tap Trail as a linear park, shaded by trees and structures for its entire 4 miles. “There’s elderly folks right now that get on that trail to get to the corner store or the laundromat and it’s just blazing hot, but it has great potential, if done right, to be a cool corridor.”

Houston’s Discovery Green is an oasis of cool. Two massive parking lots were transformed into a lush, 12-acre urban park, complete with shade trees, a water park, a performance space, and a pond.

Last summer, when strolling around his neighborhood, Pettitt saw something that stopped him in his tracks. Two houses were being built. But this time, work crews weren’t cutting trees down. They were saving them. “I was so shocked,” says Pettitt.

The architect designing the homes, Donna Kacmar, is known for her focus on the environment and use of sustainable materials. Still, she says the decision to save vegetation ultimately falls to the property owner, in this case, a woman who grew up on the site and loves the trees. “Trees help everybody,” Kacmar says. “They keep the house cooler. They’re beautiful to look at. They keep the street cooler.”

Everywhere you look in Houston, some kind of effort aimed at sustainability is taking shape. Discovery Green, which opened in 2008, is an early success story: Two massive parking lots were transformed into a lush, 12-acre urban park, complete with shade trees, a water park, a performance space, and a pond. About a mile away is Post Houston, a new, gargantuan post office-turned-food hall/office space/entertainment venue with a 5-acre rooftop park and organic farm. Greentown Labs, which says it is the largest climate tech startup incubator in North America, set up shop in Houston in 2021. Renewable energy now powers all municipal buildings. And, in a car-centric town, bike lanes now cover more than 400 miles.

To the benefit of his Third Ward community, Pettitt is driven to be a part of these changes, and he hopes to inspire other Rotary clubs to do the same. “To fellow Rotary clubs, our message is clear: Planting trees is not just about shade,” he says. “It’s about creating a more equitable and sustainable future for all.”

This is an abridged version of a story that originally appeared in the April 2024 issue of Rotary magazine

Members of the Environmental Sustainability Rotary Action Group can help your club or district plan projects and publicize your efforts.