Shade, like water, is life itself in the desert.
Sure, the sun is pretty good for a hot ball of gas. It's needed for life and plants, yada-yada. But during an Arizona summer, it's a photon-shooting Vulcan cannon. In metro Phoenix, where more people fry under extreme temperatures than anywhere else in the country, one other thing is always certain beyond death and taxes: A life-threatening heatwave will happen this summer. And next summer. Just like it has each summer for the past 10,000 years.
The sun doesn't just feel hotter here in the summer. It is hotter. Phoenix is at 33 degrees latitude, Tucson at 32 — barely over one-third of the way to the blessed coolness of the North Pole. We're practically equatorial. And Phoenix is only about 1,000 feet above sea level — a little bit lower and we'd be Death Valley. Combine high desert temperatures with a steady pounding of short-wave radiation from the sun, and any sensible creature will seek out shade. It's a survival instinct.
But shade is more than survival. It's increasingly one of the hottest topics in the urban planning industry. In this epoch of global warming, people are feeling the need for shade more than ever. People want to feel cooler in their neighborhoods, fix racial disparities, and slow the number of heat-associated deaths, which reached a record high in the state last year of 520. Local governments and universities are researching shade and, in some cases, when funds are available, putting the findings into real-world solutions like better-shaded bus stops and residential areas that can ward off the heat-island effect.
Shade is about quality of life and saving life, says Sam Bloch, a New York City-based journalist and author of an award-winning 2019 article about the need for more shade in Los Angeles. "We have to learn to see shade as a civic resource that is shared by all," Bloch says in his article, calling it "an index of inequality, a requirement for public health, and a mandate for urban planners and designers." (He's currently contracted to write a book about shade for Random House.)
"We all know we have to stop climate change ... but we know warming is here now, so the more urgent question is how do we live on this warming planet," Bloch tells Phoenix New Times. People have known something about shade for a long time, so it "becomes a nice way to talk about how we feel comfortable, and how we adapt." Beyond that, he adds, "we need to bring down these staggering death tolls."
But how? It's not just that the city is hot every summer; socioeconomic factors also make a difference in the deaths and excessive heat-related suffering in some communities. It's a complicated stew. And don't expect miracles. Making good shade is difficult, expensive, and can be water-intensive.
No, even on the hottest summer day, you can't fry an egg on a Phoenix sidewalk. It's not quite as bad here as Venus, where the surface temperature is as hot as an electric burner.
But it's bad. So bad that sometimes you have to question why you live here. An egg on a sidewalk at peak heat will cook slowly, though not completely. Eggs need nearly 160 degrees to fully cook, and concrete sidewalks may never get that hot in summer sunlight. But asphalt can get even hotter, and other surfaces may heat up even more, maybe to 170 or 180 degrees.
Last summer, the Arizona Burn Center in Phoenix admitted 104 people with burn injuries from sunlit surfaces, and seven of them died. In the Valley, "I've fallen and I can't get up" takes on an even more frightful meaning when it happens in an unshaded yard in July.
Along with the state, Maricopa County also hit a record for heat-associated deaths last year, with 323. Of those, 66 percent were caused directly by the heat, a report released last month shows. The vast majority of victims were men. Most were unhoused. In most of the deaths of unsheltered people, the abuse of substances was the cause of death or a contributing factor, along with the heat.
The problem is turning into a crisis. Heat-associated deaths of homeless people in the county have gone up every year since 2014, county data shows. One correlation could be that number of unsheltered homeless people has tripled since 2014, rising to about 3,200 in 2019, according to the Maricopa Association of Governments Point-in-Time Count. With coronavirus shutting down libraries and other places that homeless people used to stay cool, the number of unsheltered homeless heat deaths doubled in 2020.
What happens to an unshaded human on a 110-degree afternoon in metro Phoenix? Nothing good.
For starters, sunlight concentrated on your head for too long can render you stupid, according to research done by the European Union. This was a study of eight healthy men aged 27-47 who volunteered to sit and work problems while their heads and necks were irradiated from behind by lamps. The volunteers' scores on math problems and motor-skill exercises declined far more rapidly than could be accounted for by a higher core temperature, the study showed.
People have known since ancient times that too much time in the sun can break down a person's ability to think clearly. Victims of heat exhaustion often suffer from confusion. Victims of heatstroke may become delirious. Some of the heat radiation likely penetrates the skull and bypasses the brain's normal temperature-regulation system. A dehydrated person even with moderate hyperthermia isn't likely to start screwing up basic tasks — unless their head has been exposed to steady and strong sunlight.
A hat is always a good idea when under a hot desert sun. Getting out of the sun is even better.
"In the context of human physiology, to find and seek and stay in the shade — it really is the mechanism our bodies depend on to cool off in a hot environment," says Dr. Andrew Carroll, a Chandler family physician and outspoken health activist.
When people get hot, they drink more water, which allows more sweat to reach the skin. In extreme heat, a human's ability to stay cool can reach a breaking point in just a few hours. In several of the tragic cases locally in which male or female hikers succumbed to the heat, the person was dead, or nearly so, about four hours after they began their hike.
"In the sun, the skin bakes... your sweat glands are spent very quickly," Dr. Carroll says. "In the shade, we buy ourselves time."
Shade and shadows may carry negative connotations. A breezeway is a wonderful thing, but not the "valley of the shadow of death." Europeans began calling the nastier kinds of ghosts "shade" in the 1600s. "Throwing shade," a popular expression for criticizing someone, preferably indirectly and with wit, is said to have entered the lexicon in the 1980s among Black and Latino drag queens and gender nonconformists.
Here in Arizona, darkness is seen in a much better light. Shade, of course, has always had its positive side to human beings. One of the earliest forms of the word incorporates the idea that it protects people. It comes from the proto-Germanic word sceadu, which researchers believe meant "protection from glare or heat," according to online etymological sources. "Shades," as a term referring to eye protection, has been around nearly 200 years longer than Oakleys.
In the Sonoran Desert, shade helps define the landscape as much as sun-loving cacti like saguaros and cholla, and it increases the region's renowned biodiversity.
Unlike the classic landscapes of the Gobi or Sahara deserts, ours includes many native trees — not that out-of-towners will always recognize legumes like ironwood, palo brea, or mesquite as trees. The desert also supports various native deciduous trees near rivers, like cottonwood and ash, where they can replenish their moisture after dropping their leaves in the heat. The Salt River used to run year-round through what is now metro Phoenix and was lined with trees that died when the Roosevelt Dam got built and the running river was turned off.
Arizona's trees create ecosystems unto themselves in which shade plays a "super-important" role, says Elizabeth Makings, an ASU botanist and researcher.
Whether due to other plants or canyon walls, shade can help retain moisture, which enables different species to thrive than normally could in the open. To the untrained eye, the "patchy" plant life in the desert looks randomly placed, but it's not really random, Makings says. Native and non-native Sonoran plants grow where they can grow, competing with each other for water and sunlight and "communicating" to their neighbors by their actions whether it's possible to intrude closer or stay away, she says.
Some scientists believe that saguaros, which tower over the landscape arrogantly, like giant middle fingers flipping off the sun, require a nurse plant like a bushy palo verde to protect them from summer sunlight in their formative years.
"It's controversial, but it makes a lot of sense," Makings says. "You'll see saguaros underneath trees. I don't think we've settled the argument."
Birds making nests in those saguaros also take advantage of shade, usually by making nests on the cactus' north side, she says. In the winter, "they want the warmth [and] may be on the other side of that."
Microclimates in Arizona's natural habitats incorporate shade, and humans naturally have followed suit. Living in the desert requires adaptation on a scale similar to that of living in an environment with extreme cold. That means making the earth into something it's not, and creating wholly new climates and environments in miniature. With seemingly plentiful water and even more plentiful sunshine, professional and amateur gardeners have turned the Valley of the Sun into a garden of Eden. But not for everyone.
The relative lack of shade in the desert wasn't as big of a problem until millions of people moved to the state. As of 2021, more than seven million people live here, with most concentrated in the hot Salt River Valley. The place has big-city problems like homelessness, drug use, poverty, and racial disparities. The best shade and the coolest neighborhoods are where the most money is, and most of the people in these areas are white, a fact that's been underscored in this era of racial reckoning.
As the Valley hits records for the latest 90-degree day of the year, the most days over 110, and the highest overnight low temperature (94 degrees, in 2018), heat studies have shown that it's the poor and people of color who are relegated to the hottest parts of the city. These neighborhoods have plenty of heat-absorbing concrete and steel that release long-wave heat radiation, and fewer trees and other shade-producing infrastructure.
"Obviously, we have neglected a lot of communities when it comes to shade," says Stacey Champion, an activist on utility and consumer advocacy issues. "The city and the county and the state need to do a better job really meeting people where they're at. Why don't we have more shade and hydrations stations along our public transit corridors?"
Many west Valley bus stops don't even have a place to sit, much less shade, she notes.
It seems like it should be easy for Phoenix to make sure every bus stop has shade, but only 63 percent do.
Maybe more of us would take the bus if there were more shade trees next to sidewalks in transportation corridors. How we relate to the environment affects our mental and physical health, not to mention the economy. A cooler, shadier sidewalk entices people to get outside without the use of a vehicle and encourages customers to stroll along storefronts. Shadier parks reduce burns from hot playground equipment but also encourage daytime use of a park.
In 2010, the city of Phoenix launched an ambitious plan to plant so many trees in the ground that by 2030, 25 percent of the 517-square-mile desert city would be covered by a shade "canopy." Critics have long seen the goal as unrealistic, and Phoenix now reportedly needs to plant — and keep alive — 10,000 trees a year to meet the goal, more than double what it has been doing. The city is taking donations to help fund the project, although a new budget plan would "dramatically expand the number of trees we are planting ... so we hope that will cool down the city," Mayor Kate Gallego told a TV news station for a June 18 broadcast.
Tempe has a similar, slightly more realistic Urban Forest Master Plan, which was created in 2015 and aims to put a 25 percent shade canopy over the city, which is much smaller than Phoenix, geographically, at about 40 square miles, by 2040. A 2015 study showed that tree canopy cover of 25 percent in places that formerly just had bare ground saw a "total cooling benefit" of 7.9 degrees.
The plan has "an admirable goal," but the public and private sectors have to work together to achieve it, says the city's urban forester, Richard Adkins.
"I feel confident we're on a path, but there's a lot of circumstances that can happen between now and 2040," Adkins says. "I think we're having a lot of success. This year, so far, we've planted 500 trees."
But planting isn't enough. Maintenance is an obligation with trees that is not easy nor cheap. And you can't just plant them wherever you want, either. It has to be the "right tree in the right place," a common saying among arborists. You don't want branches and limbs stressing electric wires. Business owners complain when trees block their signage. Still, Tempe is moving forward with the goal and other programs designed to help its vulnerable populations and inequitable situations.
How the city will finance the program on private properties is an "ongoing conversation" that will involve continuing city support that includes the cost of maintenance and irrigation for those properties, says Braden Kay, Tempe's sustainability director. The city is using a $600,000 grant from the Robert Wood Johnson Foundation to create two youth councils of 10 kids each who will spend two years on "heat resilience" work in two of Tempe's low-income neighborhoods. (Tempe, like Phoenix, relies on public donations for its tree program.)
Other cities are catching the shade fever and wanting to plant more trees. But these plans not only cost money. They also use a lot of water. In Tempe, about 60 percent of the trees in the forestry program are non-native. What if the "mega-drought" continues for years to come, exacerbated by climate change? Lake Mead hit a historically low level last month, and scientists predict it is likely to keep dropping in the next few years. It's about 200 feet above "dead pool," the level at which no water will flow over the Hoover Dam, and the CAP canal will stop flowing.
Yet with more of your money and perhaps some advances in cloud-seeding technology, urban shade-tree programs in metro Phoenix may still have a bright future. And if not, there's always xeriscaping.
At Phoenix Sky Harbor International Airport, workers chain-sawed mature trees and installed cactus and native plants for a 2019 xeriscaping plan that is now saving Phoenix $400,000 and five million gallons of water per year. City leaders justified it by pointing out the trees and grass were not where people were walking, which is true because there is no safe way to walk in or out of the airport. The city advises against even trying to walk to or from the airport, noting on a web page that “sidewalks might be lacking.” Of course they are — who wants to walk in Phoenix, anyway?
There's one way that the entire Valley can come under heavy shade in the daytime all at once: a total solar eclipse. The next one that centers on Phoenix won't happen until July 17, 2205, but the moon's shadow does tend to cool things off here on earth when it happens, at least for a few minutes. The two gigawatts of solar energy striking the metro area will switch off, the sun's powerful rays stopped cold by a rock ball with a mean diameter of 2,159 miles and a mass of 81,000,000,000,000,000,000 tons. It's another example of how difficult it is to produce really good shade.
On a smaller scale, to the frustration of those who seek to create shade, there are many more examples of how hard this is in Arizona.
Take the Town Lake. Residents say they'd love more shade on the multi-use paths. But the lake's just a two-mile-long concrete bathtub — below the path is steel rebar and concrete, not dirt. In another area, trees could be planted there. But officials didn't want to because it would block the view of the stage for concerts in the winter. And forget about large shade sails along the lake.
"It's kind of like a wind channel — they get microbursts there," says Ariane Middel, an ASU researcher from cloudy Germany. "They take out shade sails like they are nothing."
Planners understand that making shade can involve trade-offs or negative consequences. This is where "Fifty Grades of Shade" comes in. That's the title of Middel's team's latest paper, published in the Bulletin of the American Meteorological Society's May edition. With colleagues Saud Alkahaled, Florian Schneider, Bjoern Hagen, and Paul Coseo, plus a robot-looking device named MaRTy, they made scientific observations throughout Tempe that city leaders can use to figure out the best way to make shade.
MaRTy measures three things: air temperature, surface temperature, and mean radiant temperature. It's the radiant temperature that makes the most difference to human perception, but that metric isn't just about direct short-wave radiation from the sun. It also measures the heat coming off the ground, from concrete walls, etc., that oozes long-wave radiation into your body. As the team explored breezeways, tunnels, open fields, parking lots, and other locations at different times of the day, they also took votes on their subjective perception of the thermal comfort in each spot.
"As we're talking about people and exposure, we should move away from this concept of air temperature," Middel says. "It could be 108 at Sky Harbor, 111 in Ahwatukee, but it doesn't make a difference on how you feel."
The recent study revealed a full 50 grades of shade among 1,988 observations taken at 159 different locations. It showed that shade structures "can be a viable alternative to trees in areas with infrastructure challenges," its summary states. In fact, it found structures can be even better than trees.
"During the day, at solar noon, and peak [air temperature], shade from urban form reduced [surface temperature], and [mean radiant temperature] most effectively, followed by trees and lightweight structures," the study states.
Still, ideas are easier than having the will to spend the money on all the various projects. Planners must face the reality that people continue to move here in droves without those things. But as the temperature goes up and the sun burns down, more residents demand shade. Vulnerable people need it.
"Shade is important and you should never stop trying," Middel says. "What I love about my work is I get to impact — I get to change the community. I feel like my results will not just end up on a shelf.”