CultureCap explores a defining element of life here in the Valley. This is the Throwing Shade edition.
This is actually the kick-off of a series we’re going to bring you all summer long here on the Show — a series of conversations about why shade is such a precious resource here in the Valley and why it’s so hard to create it.
For a deep-dive on shade, The Show sat down with Richard Adkins, the city of Tempe’s urban forester, and the Director of the Shade Lab at ASU Ariane Middel.
Conversation highlights
SAM DINGMAN: So, Ariane, we've had a lot of conversations here on the show about the importance of things like cooling centers in the summer, making water more available, but let's talk about the importance of shade physiologically. Why is, why is shade so important?
ARIANE MIDDEL: Shade is really important here in the valley because we have a very hot and dry climate, so the major component of the heat load your body experiences outdoors actually comes from the direct sunlight. So as as heat sources we have the short wave radiation, that's the direct sunlight, the visible light and the UV radiation, and then the long wave radiation, which is the heat that comes off of hot surfaces so when you're standing on a parking lot, the heat radiates at you, but the direct sunlight is the major component of that heat load.
DINGMAN: So we're sort of the meat in a heat sandwich in that scenario. Richard, I learned a fact recently that I was very fascinated about it. I'd love to hear more about it from you, which is that, about 100 years ago, maybe more, Phoenix was actually known as the valley of gardens and trees. Is this true?
RICHARD ADKINS: That is true. I mean, affectionately we're known now as the Valley of the Sun. But around the turn of the century in the early-1900s, Phoenix was referred to as the valley of gardens and trees. You can find a lot of historic photos showing vegetation fields, vegetable fields and fruit orchards all around Camelback Mountain.
DINGMAN: So, obviously, that is, as you were just pointing out, not the way we characterize ourselves these days. What changed? Where, where did all the trees and orchards go?
ADKINS: Well, people started coming to the Valley of the Sun. I mean, the population changed here in the Phoenix area between 1940, where it was below 100,000 people to 1960 when it was over 400,000 people.
So you had the input of people coming and then development, the advent of air conditioning that became commercially available to the average homeowner, and then in the ‘70s, I mean, really started for infrastructural development here in the Valley. The canals went underground, the streets got wider, the trees that were occupying those spaces disappeared.
DINGMAN: Can I ask you a little bit about the cultural context there? I would have to imagine that the abundance of nice places to spend time outside would have also led people to congregate in different ways, or at all.
ADKINS: Indeed, and a lot of time people were spent outside under the shade of the trees. And that was where the community was built. And so like when the air conditioning came about, people kind of went inside and that community of the environment was kind of lost.
DINGMAN: Yeah. So, Ariane, obviously, one of the results of this development and air conditioning and things like that, is that trees were once upon a time, not just an abundant source of shade, but sort of the only real significant source of it. But now by dint of development and expansion, as Richard was just saying, that's obviously a much more complicated picture, and a few years ago, you did a, a study about this. Tell us what you found.
MIDDEL: Yes, so we conducted a study called 50 Grades of Shade where we were interested in The effectiveness of different sheet types because obviously we would, we love trees and we would like to plant more trees, but there are a lot of infrastructure challenges in urban environments, so there are sewer lines underground, power lines, so there are a lot of places where you can't plant trees.
So we were interested in finding if there are other alternative shade types and we used an instrument called MaRTy. MaRTy stands for MRT because it measures the heat load of the human body, which is MRT, and MaRTy looks a little bit like Wall-Es, it has these sensors that are called net radiometers, and they, they have like these white circles and, and so we've taken MaRTy out onto the streets and parks to measure different types of shade, anything from shade from buildings, pergolas umbrellas, shade sails, different types of trees. And it turned out that that engineered shade is actually quite effective.
DINGMAN: OK. And any particular types of engineered, or first I should ask, when you say engineered shades, what, what kinds of structures are you referring to?
MIDDEL: Yeah, so this could be anything from a shade sail you put up in your backyard to a pergola or canopy. It could be an umbrella that you bring when you walk outside. So the most effective shade came actually from buildings because it's a very solid, very dense type of shade.
But that's only true during the day because buildings, they heat up during the day when the sun hits the facade and then at night they release the heat back into the atmosphere, but during the day they really provide a lot of relief from the heat.
DINGMAN: OK, well, so obviously it sounds like there are a lot of non-tree opportunities to create some additional shade, but, Richard, I know you're overseeing a number of initiatives to try to improve the urban canopy, so that we're kind of leveraging all of these solutions. One of the things I was interested in reading about your work, Richard, is that you've actually studied trees all over the world, Virginia, New Zealand, Nepal, obviously right here in the Valley. Much like all, not all shades is created equal, not all trees are either. What are the unique elements of the tree species that we have here and what can they offer?
ADKINS: Well, there's just such a variety of trees that we can grow here that actually do well. And a lot of people want to use all native species, which I think is great because they've evolved here in this climate. They're very low water use, but they also have different attributes that we have to be aware of like spines and thorns and prickles, we can't put that next to a soccer field or a play field or next to a parking meter per se.
So we really got to be intelligent in our design when we're looking at different species to plant.
DINGMAN: Ariane, is there a difference physiologically between the impacts, the benefits of shade that's created by a tree and something like a pergola or the shade of a building.
MIDDEL: In the end, it's all driven by the amount of solar radiation or direct sunlight that hits your body. So if you have a tree with a low leaf area density, like maybe tiny leaves that let through a lot of sunlight, that shade would be less performant than a denser shade, let's say from a ficus tree, for example, but it's essentially driven by the amount of direct sunlight that hits your body.
DINGMAN: I see. Well, so let's talk a little bit more about this, these environmental questions, that you were just kind of alluding to, Richard, and how the placement of the trees, and I have to imagine the specific type of tree, are really important when we're looking at this.
Let's talk about the infrastructure concerns, because it's some people might be hearing this and thinking like, you know, what, what's so hard about just planting more trees? Why, why is that, why is that controversial? But tell us a little bit, Richard, about why that it's not as easy as it sounds.
ADKINS: Well, it's basically a matter of space, and we look at soil budgets when you're trying to put a tree in a dense urban environment, and it's got to have space for the roots to really expand and grow for the tree to reach its genetic potential. And some of those areas are just not available in some of our developing areas. That's where the engineered shade is actually makes a very good alternative in certain areas.
DINGMAN: Are there similar infrastructural challenges to engineered shade?
MIDDEL: Yes, there is an example for, I was talking to, someone from the city of Tempe. It's, it's a while ago, and, I think it was Bonnie Richardson, and we were wondering why there's no shade along Tempe Town Lake of either trees or or engineered shade and …
DINGMAN: Now that you point that out, there is no shade there is no shade.
MIDDEL: But the problem is that there is a support structure for the lake that prevents anything to be built very close to the lake. And so there are challenges with engineered shade structures as well.
DINGMAN: So one of the other things that the specificity of that Tempe Town Lake example brings to mind for me, Ariane, is that I know you've done a lot of work on heat mapping, And the the ways that heat and and sunlight are present and particularly intense or or less intense in various parts of the city. Talk about how you put those maps together, and why they're important.
MIDDEL: We use a model … to create these heat maps, and these heat maps show the mean radiant temperature, which is the heat load on your body at a very high resolution, 1 meter resolution. And we have these maps for all of the Phoenix metropolitan areas, and these maps can be used to figure out where are the hot spots in the Valley.
There are definitely parts of the valley that have less shade than others, and it could be either shade from buildings or trees. It doesn't matter. So those maps can be used to make decisions on what are the priority areas to plant more trees or provide more shade in general.
DINGMAN: I have to imagine that there are some areas where an engineered solution might work better than a tree solution, right?
MIDDEL: Yes, if you look at these parking lots, they're usually pretty harsh environments for trees. So you might think about putting up solar panels because they shade cars as well as, or maybe even better than trees, and they have a higher survival rate.
DINGMAN: I wanted to talk a little bit about the urgency of this because so far we've been Kind of looking at shade from a theoretical standpoint, but I think it's also really important to talk about from a practical standpoint why this matters so much. our average summer temperature in the valley, as everybody listening to this knows, is in the 100s. That's the average temperature.
Earlier this year, I spoke to a postdoctoral researcher at USC named Eun Young Choi. Her research suggests that heat here in the Valley doesn't just create, like, momentary crises, like heat stroke, exhaustion, dehydration. This research actually suggests that living in extreme heat is aging our cells significantly faster, 14 months faster, to be exact.
Now, obviously this is just one study, but that was stunning to me, and Ariane, I know you've done some work looking at the phenomenon of, of heat's impact on the body, right?
MIDDEL: Yeah, I mean, heat affects everyone here in the Valley. It's not just, I mean, people die from it all, but, but everybody is subject to heat stress, essentially when you're outdoors, walking, waiting at the bus stop for your next connection. So what happens is because it's such a dry heat, you need to really be hydrated a lot to keep your body going. And you're sweating a lot, so it's really, really important to, to keep, keep yourself shaded in the summer when, when it's above, well, even when it's above 90.
DINGMAN: Yeah, and, you know, as tempting as it is, Richard, you were alluding to the phenomenon of, you know, how pervasive air conditioning is in the Valley to accommodate our ever expanding population. As tempting as it is when it gets really hot to go inside and just escape the heat, I know that for you, being out in nature is really important and cultivating, as I understand it, kind of a personal relationship with not just shade, but trees in general. Can you talk a little bit about this? I know you're a proponent of something called forest bathing.
ADKINS: Oh, indeed. Trees’ good shade, physiological shade, of course, is quite important for our standard of health, but also our mental health as well. That's a lot of the benefits of urban forests that people do not really realize and so I mean, it is warm and we kind of acclimatize as we go through the summer, but you can see about August and September here in the Valley, people's mental acuity seems to start to go down and people, you know, tempers get a little bit quicker.
But not being able to get out and have a better standard of life, quality of life with green spaces and being able to go out and experience trees and plants really does help one's mental health.
DINGMAN: Can I ask you what that looks like just to speak from your own experience, like, if somebody is hearing that and thinking, I don't know how to start, like, should I just go and stand next to a tree? I realize this probably sounds a little simplistic, but how do you approach that when you're trying to kind of reestablish your own connection from a mental health standpoint?
ADKINS: I think standing next to a tree is actually a good start, but a grove of trees, even. It could be in your backyard, in your local neighborhood park. Sometimes if you want to drive into one of our preserve areas here in the Valley or out on South Mountain Park, or even if you need to go up north, perhaps to get up on the rim and get it more into our Ponderosa Forest.
It's just more of your own personal approach as you go into the forest. It's welcoming you and you're welcoming it, so it's more of a very experiential type tactile thing. You need to touch the trees, feel the trees, feel the soil, and just kind of experience the wind blowing, the animals, the birds. I know it sounds very esoteric, but it really does open up one's mind and really see the forest for the trees.
DINGMAN: Ariane, has this come up in your research at all? I know in one of the studies that you did, I saw a stat that was something like the body temperature can go down by as much as 30% by spending time in the shade. That's pretty significant. Have you looked at all the psychological impacts that this has on folks?
MIDDEL: I've not done any studies personally here in Phoenix on the psychological impacts, but I've read in the literature that trees have a lot of other benefits, especially to your, to your mental health as well. There's a study that was conducted in a hospital, and the researchers looked that patients in beds that were facing the parking lot versus facing the forest area or, you know, a park, and those patients healed much quicker than the patients that were facing the parking lot. So, there is a huge mental health benefit that trees offer that engineer shade would not.
DINGMAN: Well, so we've been talking about kind of the softer side of trees. Let's talk about some of the really concrete efforts that the Valley is making to increase the number of trees that we have available to us. Richard, one of the initiatives related to this is something called tree equity. And Phoenix has made a very aggressive commitment to tree equity, trying to reach this standard known as tree equity by 2030. Tell us what tree equity means and how are you working on that here in Tempe.
ADKINS: All right, well, there's a number of cities within the Valley that are focusing on that, and Tempe, of course, is one. Well, the whole thing is equity, as we mentioned earlier, not all parts of a city are shaded equally. Due to some past history or development, anywhere within our census tracts that shade ranges from 25% in some neighborhoods down to 5 and 6% on other neighborhoods or, you know, development parks.
So the whole thing is trying to bring that average up and provide everybody an equal opportunity to have shade and experience the benefits that trees provide.
DINGMAN: So within that, you launched something called the Urban Forestry Master Plan back in 2017, if I'm not mistaken.
ADKINS: The city adopted it in 2017.
DINGMAN: The city adopted it, OK. The goals contained within that, that's, that's for Tempe specifically, correct?
ADKINS: Correct.
DINGMAN: The goals are very ambitious. Tell us what the benchmarks that Tempe's working towards are.
ADKINS: Right now we are looking at updating our Urban Forestry Master Plan, but right now the benchmark is merged at 25%, and we're sitting at 14.5%, one of the highest shaded cities here in the Valley.
DINGMAN: OK, and the goal was 25% by …
ADKINS: By 2040.
DINGMAN: OK. So, a good portion of the way there. One of the interesting, you know, we're talking a moment ago about the broader impacts of something like trees. One of the things that was interesting to me about the Urban Forestry Master Plan is that it's part of a larger initiative, if I'm not mistaken, to make Tempe something called a 20-minute city. Yes, tell us what a 20 minute city is.
ADKINS: Well, a 20-minute city is being able from your home within 20-minutes to provide, to get to all whatever you need, whether it be shopping, whether it be school, whether it be to work, and be able to do that comfortably. Perhaps be in a shaded corridor, but to be able to comfortably get anywhere within the city within 20 minutes.
DINGMAN: So the idea there is that shade is, is a big part of that because it makes the city, I guess, more walkable.
ADKINS: Absolutely.
DINGMAN: OK, which I would imagine would also encourage things like construction of like neighborhood shops.
ADKINS: Exactly, and being able to go from, say, a shade node to a shade node, there might be some areas where there's, you know, no shade or you have some more solar radiation, but you'd be able to go from area to area within a short amount of time.
DINGMAN: OK. Ariane, let me ask you, you know, beyond trees, as you look around the city, where do you see, just from your own opinion, having done all the research you've done, where do you see opportunities to create more shade, innovative solutions, things we could be taking advantage of that we're not currently.
MIDDEL: We have a lot of impervious surfaces here, a lot of parking lots. We put so many parking lots next to our shopping malls that Black Friday can be accommodated, but the rest of the year they're they're they're essentially empty. So those parking lots have an extensive surface and definitely need more shades.
It would be a lot of opportunities to put solar panels on these parking lots that produce electricity at the same time. So if you have PV cells that produce electricity and then at the same time shade those cars, that would be one option because we have so much solar radiation here, it's a missed opportunity.
DINGMAN: Richard, same question.
ADKINS: I'm gonna say same answer. We have recently measured all of the impervious areas surfaces here in the city of Tempe and being able to reduce those or either have some kind of perhaps a management fee for having large parking lots because you have a lot of storm water runoff from all of those whenever it does rain, so that's another thing that we need to look at and we can capture some of that water to help water and grow trees in some of those areas.
DINGMAN: We've got just about a minute left here. I'm curious if either of you have a favorite shady spot you'd like to recommend either in Tempe or just around the city.
MIDDEL: There's a really, really nice large ficus tree next to the Memorial Union on ASU's campus. I really like that tree, yeah.
ADKINS: There's some areas in the Tempe Preserve. It's called LoPiano. It's right off the side of the freeway. There's some very nice lots of mesquite trees down there. It's a very pleasant place to go.
DINGMAN: OK, so maybe some aromatics to go with your shade.
