How America's hottest city is trying to cool down

Can trees help save Phoenix from extreme heat?

It’s time to stop looking at trees as a form of “beautification.” They are, instead, a living form of infrastructure, providing a variety of services that include stormwater management, air filtering, carbon sequestration, and, most importantly for a city like Phoenix, Arizona, they cool the environment around them.

Trees can lower neighborhood temperatures in three ways:
1) Their shade prevents solar radiation from hitting paved surfaces like concrete and asphalt, which absorb energy and rerelease it into the air as heat.
2) Their leaves pull heat from the immediate area in order to evapotranspirate water that’s drawn from the soil.
And, 3) If you’re standing under one, a tree protects your body directly from the sun’s rays. If you’ve ever made a summer visit to a dry, hot city like Phoenix, you’ll know how important shade is for making any outdoor experiences tolerable.

As Phoenix deals with a rising frequency of extreme heat waves — which aren’t only deadly, but also cause worrisome spikes in energy demand — the city is looking to trees as part of its heat mitigation strategy. Phoenix isn’t devoid of trees, but they’re distributed unevenly across the city. A quick glance at a satellite image of the metro area reveals substantial green splotches in the north and east and brown ones in the south and west, where many lower-income neighborhoods are located.

So Phoenix recently pledged to reach “tree equity” by 2030, under an agreement with American Forests, a national tree organization. I visited Phoenix recently to take a look at the current state of the city’s urban forest. In this video, we use drone imagery and thermal cameras to understand how the urban design of the city contributes to extreme heat, and what it can do to cool down.

Further reading:

[Vox]

Thanks for watching and commenting! Quick note for those saying desert cities "shouldn't exist" ... that's a very tempting thought, one that I admit I shared when walking around Phoenix in August, but keep this in mind: Heating uses more energy than cooling. I think cities with frigid winters are older and more established in the US so we think they're normal and assume their right to exist but walking around Chicago in January is as painful (maybe more?) than a Phoenix summer. We can't all live in San Diego, so rather than condemn entire cities in the west, it's more helpful to think about how we can plan, adapt, and re-design to make them more sustainable and livable in the future. -joss

[Wasserkaktus]

I've lived in Phoenix nearly my whole life. When I finally bought my own house a few years ago, I decided to plant several trees in what little yard I have in order to lower temperatures. The result is, my yard is literally several degrees cooler, plus since you can grow tropical AND temperate plants in Phoenix, I grow my own peaches, mangoes, guavas, Barbados cherry, pomegranates, almonds, grapes, and bananas, among other annual plants like squash.

[LemonToGo]

Also, biologically speaking, trees do not only cool through shade. Trees "sweat out" water at the leaves in a process called transpiration. It cools the air around the leaves.

[Lemonz]

People don’t seem to realize city design in the US is atrocious, which contributes to this problem. Many are sprawling, sparsely populated, and have way too many large roads and giant parking lots, and are quite frankly, unsafe for pedestrians, children and cyclists. You need a car or public transportation just to go on a grocery run - it’s ridiculous.
This makes most of the city unproductive with regards to income and tax revenue and expensive to maintain, causing cities to run a budget deficit just to maintain basic infrastructure. Good old fashioned city design with modern innovations where shops and people live next to each other are comfortably walkable and can produce enough revenue to maintain itself, including its trees and parks. No need to make people pay out of pocket for projects the city deems necessary, like this tree project, because it can’t afford them. Walkable cities also produce natural shade.

[mattdc]

I live in San Jose, CA. Here each and every tree between the road and sidewalk is owned and managed by the city. Individual homeowners cannot touch them. It is nearly impossible to have them removed. It works, there is lots of shade and it provides value to everyone.

[lakesideparkplace]

It’s suppose to cool off after the sun sets. the ground shouldn’t hold heat in the desert. But Phoenix stays hot all night long because of the concrete

[doomnipple]

As a professional Forester...I can confirm.

Also trees reduce heating costs via wind reduction. They also increase property value, improve wildlife habitat, reduce soil erosion, filter water, sequester carbon, cycle soil nutrients, and provide wood products (lumber). Trees are awesome!!

[Dovietail]

Every parking lot in Phoenix should have a solar panel shade structure over it that is both gathering energy AND shading all that parking lot cement.

[duprie]

I live in Melbourne Australia and although it's nothing like Phoenix we do get occasional heatwaves with temperatures over 40°C/105°F. 13 years ago we planted a London plane tree in the west facing front yard just for looks, but now it shades the whole front of the house in summer and the difference inside on hot days is just amazing. A massive bonus we never even expected. Trees are awesome!

[ShreyasBharadwaj]

Love the constant drone camera shots to reemphasize the sheer dryness of the street. As someone who has walked on these streets regularly in peak summer, it’s hard to explain how terrible an experience it is.

[plshelpalistair]

Citizens: “Please we need trees”
Cities: “Sorry, did you say parking lots? Because I’m pretty sure you meant parking lots.”

[JulioLopez-jojn]

Phoenix native here, it’s a blessing to get anywhere from 95-103 degrees during the summer nights. Anything after 7am.. better keep yourself home

[samanthasowers]

I recognize this area and I can tell you guys from living here for all my life so far, I have seen dogs suffering, people wanting fresh air but you really can't go outside. We need to find a way to cool Phoenix down, but without ruining our water supply even more.

[siddharthbelwal]

Yup. Same situation in LA, the rich neighborhoods like Beverly Hills are covered in trees and feel relatively cool even when it’s really hot, while poorer neighborhoods like in south central have no trees and feel like an oven at the same temperature

[Nextraker]

I hate not being able to walk my dog till after sun sets here in phx

[bxnjiijusticeforukraine]

I live in Phoenix and this is an amazing representation of the heat and offers a great story!! Thank you for creating this.

[jlitow]

I'm 38 and have lived in Arizona since i was 6 months old. I have lived in central Phoenix, Scottsdale, Mesa(where i currently reside), Gilbert and Glendale. I can attest to the considerable heat difference between areas like Scottsdale and other higher income areas compared to lower income areas like mesa and phoenix. I really hope they do follow through with creating more natural canopy. A lot of areas could really use it. Regardless of the heat i love this state.

[diegovasquez]

As a Phoenix native it would be really great to plant trees, but the problem now is water because we’re kind of running out, but maybe planting mesquite or palo verdes will help? They don’t really shade as much but they kind of help

[TwoOneFo]

Was in a Phoenix one time in my life, and coming from Texas it was a great zip through the mountains, and the cold air up there was great, while still seeing a desert.... then we got to Arizona and to Phoenix and I’ve never felt worse. 118 degrees in the shade. And this was in May. Sandals melted on the sidewalk... miserable

[AndreKlebleyev]

The heat is pretty terrible, I’ve lived here for 3 years and my house is luckily in Mesa because all the outer towns are easily 3-10 degrees cooler in peak summer over downtown Phoenix. I work in downtown right off of buckeye close to the neighborhood they’re talking about and the video is 100% correct it’s a massive difference going from nice Tempe Scottsdale north Phoenix neighborhoods and south side Phoenix which just looks like a dry concrete desert. (But I am moving out of this state within 3-4 months) summer heat keeps getting worse very realistic to have a good 1-2 months of 110-115F every single day and I’ve had days where I’ve walked my dogs in the park and at 9pm with the sun set the air temp was still 108f