Summers in Phoenix pose a daily health threat to Leonor Juarez and her family. She and her five children have asthma, and struggle to breathe the ovenlike air that ripples off the sidewalks when they walk their neighborhood’s shadeless streets. The sun beats down on them at uncovered bus stops during the five-hour round-trip to the doctor, leaving them suffering headaches, dehydration and chest pains. “It feels like I’m having a heart attack,” Juarez says. “It feels like you’re drowning in a swimming pool or you have a pillow over your head.”

Stories like Juarez’s are not unusual in Phoenix, the nation’s fastest-warming big city, which hit triple-digit temperatures on 128 days last year—and where at least 172 people died of heat-related causes in 2017. With the urban heat island effect acting in concert with global warming, U.S. cities could be up to 10 degrees Fahrenheit warmer in the afternoon and 14 degrees warmer at night by the end of the century, according to a recent study in Nature Climate Change. As temperatures spike, researchers and urban planners worry heat deaths will rise across the country.

So Phoenix has launched two revolutionary initiatives: HeatReady—the nation’s first program of its kind—treats heat readiness like hurricane readiness and heat waves like temperature tsunamis. It will alert residents with text notifications and offer emergency cooling centers. Another project, Nature’s Cooling Systems, is redesigning those low-income neighborhoods hit hardest by heat to remove some of the sting. Both programs emphasize close cooperation with residents and could provide a model for other cities. “Phoenix is definitely on the forefront,” says Melissa Guardaro, a research fellow at Arizona State University’s (A.S.U.) School of Sustainability. Heat, she adds, “is a huge public health concern.”

The HeatMappers Walk, a public science event, was held in a central Phoenix neighborhood with low tree canopy to gauge the impacts of heat on residents. Credit: Ash Ponders The Nature Conservancy

Where Heat Hits Hardest

Extreme heat is one of the leading causes of weather-related deaths in the U.S. City-dwellers are particularly vulnerable because asphalt and metal absorb and then release the sun’s energy, creating the urban heat island effect that magnifies heat waves. But heat is not an equal opportunity killer: Heat stroke and death occur disproportionately in lower socioeconomic areas, where mosaics of dirt lots, asphalt and sparsely landscaped houses can bake 10 degrees hotter than wealthier, lusher zip codes. To address the issues in these extra-hot archipelagos, Nature’s Cooling Systems (NCS)—a partnership between The Nature Conservancy, A.S.U. and the Maricopa County Department of Public Health—is weighing a range of design changes to make neighborhoods safer and more comfortable.

Shade trees are the most natural solution. In a desert city like Phoenix, that might mean planting mostly drought-tolerant native trees that cast light, lacy shadows—and interspersing them with leafier, thirsty trees where people can congregate, says Guardaro, who is part of the NCS team. Phoenix is ramping up efforts to meet a 20-year goal set in 2010 of achieving 25 percent tree canopy coverage, which will reduce temperatures nearly 8 degrees compared with bare areas.

NCS is also considering architectural measures such as shadow-casting art pieces that, without the need for water, could beautify barren neighborhoods, as well as orienting new buildings so they bathe sidewalks and courtyards in blocks of shade. Architects are additionally contemplating a return to traditional materials such as adobe as well as courtyards featuring evaporative cooling towers and trees—which together could cool buildings by up to 30 degrees—says Maggie Messerschmidt, urban conservation program manager at The Conservancy’s Arizona chapter. Solar panels could also be positioned over parking lots, where they would shield sizzling blacktop and prevent cars from turning into mobile furnaces, Guardaro says.

Not every solution will work well in Phoenix, though. For example, the city’s dust storms would render impractical the whitewashed “cool roofs” and streets that have been proposed in parts of California, Guardaro says. Some Phoenix parking lots, however, have been covered with pale, pervious pavement that has the texture of a Rice Krispies treat. It allows stormwater to seep in and heat to escape at night, reducing surface temperatures by 27 degrees compared with asphalt.

NCS has planted some trees and is now examining which solutions might be best for various neighborhoods. To evaluate what works, A.S.U. has installed weather stations throughout Edison–Eastlake (one of the three neighborhoods involved in the initiative) to compare surface temperatures before and after redesign. The project aims not just to drop the mercury a certain number of degrees but to provide tools to help those who live there be more resilient to heat when it hits. For that, the researchers are turning to the residents themselves.

Building Trust and Gathering Stories

On a 100-degree F afternoon late last September more than a dozen volunteers, including residents, strapped on UV monitors and temperature gauges and walked around Edison–Eastlake. They sweated profusely and burned their thighs on metal bus stop benches, as researchers peppered them with questions about how they would like the city to address the need to cool the streets and playgrounds.

The walk is part of NCS’s effort to revolutionize urban design by inverting the traditional top-down approach in which city planners dictate design from air-conditioned high-rises, routinely failing low-income areas. The program—along with a handful of other revitalization projects burgeoning around the country—views locals as experts on their neighborhoods. The researchers are building trust by listening to the lived experience of heat-vulnerable residents like Juarez, and by calibrating changes to residents’ specific lifestyles. At one NCS meeting, when Juarez told a story about running out of bottled drinking water during a trip to the doctor, it opened city officials’ eyes to the lack of drinking fountains on public transit and pedestrian routes. One planner proposed combining misted bus stops with drinking fountains and drip irrigation for shade trees, because these features could share a water source. “It has been very important to use story as a way to explore how people are already coping [with heat], what kinds of strategies might help people cope better and where specific mitigation strategies would be most useful,” Messerschmidt says.

The HeatReady program also engages residents by asking them where cooling centers should be located. “We were able to get a lot of really important data from them,” says Chief Service Officer Michael Hammett; this included the need for cooling centers that allow pets and the idea to install misting systems and rotating blinds at bus shelters.

Hurdles Remain

But all these solutions face hurdles—especially in the neighborhoods that need them most. At one meeting a city official told residents cooling amenities are prone to vandalism, so he urged them to be more vigilant about reporting crime. A woman responded that when she called the police to report vandalism, they accused her—and when she testified against the perpetrators, someone tried to burn down her house. NCS is advocating for the city to create more welcoming avenues of communication, including ones for non-English speakers, so residents feel comfortable reporting crimes and making suggestions to decision makers, Messerschmidt says.

Another worry for residents is that improving these neighborhoods will attract wealthier newcomers who inflate housing prices, thus forcing out the original residents. The redesign of Edison–Eastlake is funded by a federal Housing and Urban Development grant that requires the city to keep housing affordable in perpetuity, but in areas where that is not the case, communication and inclusion play a key role. “Part of a way to alleviate the possibilities of gentrification is by including residents at the table and the decision-making process,” says senior fellow Kristin Rothballer of the Center for Whole Communities, which helps the The Conservancy and urban conservation projects focus on equity and justice. “By having more kinds of stakeholders at the table, you’re going to be able to strategize ways around potential roadblocks.”

Guardaro agrees: “I think the biggest hurdle is that mitigating heat is nobody’s responsibility, yet it’s everybody’s concern,” she says. “So we’re trying to get as many people together [as we can] to talk about this and make urban heat a primary concern.”