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By 2100, Sacramento is expected to feel much like Phoenix, which last year had more than 100 days over 100 F. In this Unfold episode, co-host Kat Kerlin discusses her “Becoming Arizona” series, which looks at how to prepare for a hotter future. We also examine how cities nationwide are dealing with triple threats: rising temperatures, racial inequities and a pandemic. And we’ll discuss the efforts needed to build socially just, climate-resilient communities. 

In this episode:

Mary Cadenasso, professor, and landscape and urban ecologist at UC Davis

Stephen Wheeler, professor of landscape architecture and urban design at UC Davis

Helene Margolis, associate adjunct professor in the Department of Internal Medicine, UC Davis School of Medicine

Adrienne Lawson, senior director for the UC Davis Office for Health Equity, Diversity and Inclusion

Victoria Dearborn, graduate student in the Cadenasso Landscape and Urban Ecology Lab 

Victoria Vasquez, South Sacramento NeighborWoods organizer, Sacramento Tree Foundation

Kat Kerlin: Hey, Amy. You been to Arizona, right? 

Amy Quinton: Oh, yeah. Gorgeous state. I actually got to raft down the Colorado River through the Grand Canyon with a UC Davis class a few years ago. It was amazing. 

Kat Kerlin: Dude, I know I invited you. 

Amy Quinton: Oh yeah. Right. 

Kat Kerlin: Ok, so have you ever been there in the summer? 

Amy Quinton: Yeah, actually. I used to live in Phoenix when I was a kid. 

Kat Kerlin: Really? Well, I have a ton of family there, so I’ve visited a lot. It never really cools down in the summer. I mean, never. 

Amy Quinton: Well, I live there and like the late 70s and early 80s. So that means I'm old. But I remember it being really hot. But I had a pool and I was a kid. And kids don't mind anything if there's a pool. 

Kat Kerlin: That is true. Well, to refresh your memory, in August, you can go outside at 3:00 in the morning and it is still in the 90s. 

Amy Quinton: They say it's a dry heat, though. 

Kat Kerlin: Yeah, but it's still really bad. I mean, last year, Phoenix had 100 days over 100 degrees. 

Amy Quinton: Oh, my God. 100 days? That's crazy. Why does anyone live there? 

Kat Kerlin: Oh, now, don't get me wrong. I actually love Arizona. But for comparison, Sacramento, where we live, had nine days over 100 last year. So I was a little taken aback when I read California's 4th Climate Change Assessment that UC Davis led for the Sacramento Valley. It said that our region could expect to feel much like Arizona by 2100 at the rate we're going with climate change. 

Amy Quinton: I'm so glad I'll be dead. 

Kat Kerlin: That's one perspective. 

Amy Quinton: Dude, I read that the number of extreme heat days, those over 103 degrees Fahrenheit, would grow from just four days a year to 40 by the end of the century. And that's an average. I mean, there could be more days. I can't imagine that. I mean, how is Sacramento going to deal? 

Kat Kerlin: You know, I wondered the same thing, so I decided to dig in. It resulted in a five-part series of articles called Becoming Arizona. It's on our climate website at 

Amy Quinton: And it's awesome. 

Kat Kerlin: Thank you. It doesn't dwell too much on these shocking changes to come. Instead, I looked at how the Sacramento region can prepare for these changes now and maybe even prevent some of them. And by the way, this is not just specific to Sacramento. There are lessons for how many cities can prepare for a hotter future. 

Amy Quinton: But wait, even in a pandemic? 

Kat Kerlin: Even in a pandemic. But it's going to take some work.

Amy Quinton: Naturally.

Kat Kerlin: Because just like with climate change, it's the poor and vulnerable people who are affected the most when it comes to rising temperatures. And we're going to talk about that as well in this episode of Unfold. 

Theme: Coming to you from our closet studios as we shelter in place across the Sacramento region, this is Unfold, a UC Davis podcast that breaks down complicated problems and discusses solutions. 

Kat Kerlin: This week, we unfold Becoming Arizona. I'm Kat Kerlin. 

Amy Quinton: And I'm Amy Quinton. 

Amy Quinton: So, Kat, when I think about how cities are going to adapt to warming temperatures, I just think people will crank up the AC and a lot of us are just going to have to suffer through it all. 

Kat Kerlin: There are ways to help cool warming cities besides cranking the AC, which, by the way, can crank up the carbon too. So clean, reliable energy is also really important. But it turns out a lot of heat-related illnesses are actually preventable. And when I began to research this topic, it became obvious really quickly that disadvantaged communities are the most vulnerable. 

Amy Quinton: And by disadvantaged communities, you mean communities that suffer a combination of economic, health and environmental burdens? 

Kat Kerlin: That's right. And those communities are predominantly comprised of people of color. 

Amy Quinton: And now we're also dealing with a pandemic. So really, Sacramento and so many cities nationwide are dealing with triple threats. 

Kat Kerlin: Exactly. Rising temperatures, racial injustice and a pandemic. 

Amy Quinton: Good times. 

Kat Kerlin: Before we unfold all that, we need to first understand what makes cities hot, because it's not just about the temperature outside. It's also about the built environment. You've heard about urban heat islands, right? 

Amy Quinton: To some degree. Get it? Degree? 

Kat Kerlin: Oh, Amy, you are too punny. So urban heat islands are cities that are significantly warmer than their surrounding non-urban environment. So Phoenix is an urban heat island. And when nighttime temperatures drop in the desert that surrounds it, the city remains hot. 

Amy Quinton: So for Sacramento to be a heat island, it would have to be a lot hotter than, say, the grasslands and ranch lands that surround it. Jeez, is that what we can expect? 

Kat Kerlin: What Sacramento is dealing with is an urban heat island effect. So we have a little pockets of heat within the city where there are very few trees, little shade and a built environment that soaks up heat and releases it into the air. 

Amy Quinton: So really they are more like heat archipelagos, little islands of asphalt perhaps? 

Kat Kerlin: You could say that. And this is something that Mary Cadenasso, a UC Davis urban ecologist who's in the Becoming Arizona series, talks about. 

Mary Cadenasso: There are certainly places with no tree canopy and lots of heat generating activity; cars, buses, light industrial, those all generate heat - people running their air conditioners. Those all generate heat and if there isn't anything to take away that heat or to prevent that heat like a tree canopy, there are some places in the city certainly that are hotter than the surroundings. 

Kat Kerlin: Several studies from Baltimore and Phoenix to L.A. and Sacramento have shown there can be as much as a 10-degree difference between neighborhoods with a nice shady tree canopy compared with neighborhoods with few trees. Trees can really be a simple yet amazing climate and health solution. Sure, they offer beauty, but also cleaner air and shade. 

Amy Quinton: Okay, tree hugger. Seriously, though, 10 degrees can be a huge difference in how hot it feels. I mean, to me, like 85 degrees is tolerable, but 95 is way too hot. 

Kat Kerlin: Yeah. And the temperature differences can exist even though the neighborhoods might be just a few blocks away from each other. 

Amy Quinton: And those differences may even exist on a finer scale. So, Kat, you pointed out in your Becoming Arizona article on heat islands that Mary was launching some research over the summer on heat in Sacramento. 

Kat Kerlin: Yeah, and how things like tree canopy and vegetation play a role in temperature differences, as well as tradeoffs of planting trees while still trying to conserve water. 

Amy Quinton: Right. So I had the pleasure of meeting up with her and her graduate student, Victoria Dearborn, in East Sacramento as they did their research. 

Kat Kerlin: And if you don't know, that's an older tree-lined neighborhood. 

Amy Quinton: Yeah. Big trees in almost every yard. 

Amy Quinton: So we're on the sidewalk in front of a home in East Sac and Victoria picks up what looks like a jetpack and straps it onto her back. She then sets up a tripod with all sorts of strange gadgets attached to it in a resident's front yard. 

Victoria Dearborn: This is our meteorological station that we use to measure microclimate in Sacramento. So, this station is recording things like air temperature, how humid it is, the wind speed and direction and also this sort of fancy dangling bit here tells us how much radiation is actually reaching the top of this station from the sun. 

Amy Quinton: Victoria is measuring the thermal comfort or what the temperature feels like for the homeowner who lives here. 

Victoria Dearborn: Heat is the biggest risk and danger to urban residents in terms of all climate disasters. It's more deadly than hurricanes. It's more deadly than floods. And it doesn't get that sort of attention. So I feel like it's a really ripe space for more research. 

Amy Quinton: But along with the heat that comes with a changing climate, so too does drought. After the megadrought California experienced just a few years ago, Mary Cadenasso says a lot of Sacramento residents are changing their yards to drought tolerant landscaping to save water. 

Mary Cadenasso: What we're really concerned with is this tradeoff between saving water but exacerbating, unintentionally exacerbating the urban heat. 

Amy Quinton: Mary says about 10 percent of the front yards of single-family homes in Sacramento have drought tolerant landscaping, which usually means a ground cover of plants that don't need much watering or rocks or mulch or some combination. She takes me to a drought tolerant yard. 

Mary Cadenasso: So there's California fuchsia, there's Tiger Tails or Ceanothus. So some are native and Californian plants. Some are native to other arid landscapes. So the house itself is in full sun. It doesn't have a canopy tree yet, but two trees have been planted in the hopes of getting it. 

Amy Quinton: She says a number of factors play in to how hot a yard feels. An irrigated landscape cools down a yard, but so do landscapes with drought tolerant groundcover since plants transpire. It's noon and about 93 degrees. And standing in this yard it feels fairly hot. Then Mary takes me next door. 

Mary Cadenasso: This is a yard that has what we are calling more conventional landscaping. So it's covered in turf. It has a shade tree. It's relatively young. So it's still growing, but it nicely shades the whole front of the house. These are relatively small yards. 

Amy Quinton: No doubt this yard feels cooler. But Mary says it's also incredibly water intensive. Then she points to the yard across the street. 

Mary Cadenasso: The people across the street have chosen to do something different. They have a very mature London plane tree in the front yard. They also have covered it instead of with mulch. They've covered it with volcanic rock that's very dark. 

Amy Quinton: It's drought tolerant, but also shady. That might provide the perfect balance cooling down a yard and using less water. 

Mary Cadenasso: We expect to find that people who have transformed their yards to drought tolerant and are not under a tree canopy, they will be hotter than neighbors who have lawns and are also not under a tree canopy. We expect that difference to be much less when there is a tree canopy. 

Amy Quinton: But they don't know that for sure. That's why they're doing this research. 

Mary Cadenasso: So one of the questions I'm really interested in is we can scale this up to a whole city and figure out like how many yards can transform and in what patterns before we start to see a signal at the city scale where the whole city just becomes hotter. 

Amy Quinton: So, Kat, just as you said, and your Becoming Arizona series, trees could make a big difference in helping a city cool and we might still be able to do that with drought tolerant landscaping. 

Kat Kerlin: In the series, Mary also talks about other cooling solutions aside from trees. They include planting other types of drought tolerant plants along things like road medians, greenways and over bus stops. 

Amy Quinton: Yeah, who wants to bake in the sun waiting for a bus? 

Kat Kerlin: Right. Shade could actually encourage the use of public transportation, which is taking a hit in the pandemic. A cooler path is also more inviting to cyclists and pedestrians. She also talked about creatively using hardscapes like the downtown farmer's market in Sacramento. It sits under a shady rumbling freeway. 

Amy Quinton: Stephen Wheeler, a professor in the UC Davis Human Ecology Department, also talks about the need to change what he calls the built form. 

Stephen Wheeler: By which I mean buildings, the height of buildings, the presence of shade-covered walkways, courtyards, architectural devices that will keep people comfortable at ground level and will create islands of shade that preserve coolness in the city. 

Amy Quinton: That's cool. I never thought of that. 

Kat Kerlin: Yeah. Things like cool roofs and cool pavements can be integrated into the built environment to reduce heat absorption. Even simple solutions like painting homes and buildings in a light color can make a difference. 

Amy Quinton: You know, a lot of hot cities in the Mediterranean do this type of thing. So it just makes sense that we should, too. 

Kat Kerlin: Speaking of hot cities, Stephen is also doing research that looks at heat in 20 southwestern cities and he's mapping them by census blocks. 

Amy Quinton: Those are about the size of city blocks. 

Kat Kerlin: Right. And he's mapping heat along with social demographics. 

Stephen Wheeler: We are developing heat maps that show the hottest areas within each metro area and the coolest areas and the whole gradation in between and correlating those with demographics. And within most metro areas, you have at least a six-degree temperature difference on an average day, summer day, between the hottest and coolest neighborhoods - and that correlates very much with income. 

Amy Quinton: And Kat, I imagine this doesn't surprise you at all because in your series you examine this kind of thing firsthand in Sacramento. 

Kat Kerlin: Yeah. So a few months ago, Victoria Vasquez with the Sacramento Tree Foundation took me on a driving tour of the community she serves in South Sacramento, which is one of the more disadvantaged parts of the city. We drove by apartment complexes and rental units with little to no trees at all. 

Victoria Vasquez: Sacramento simply did not build tree-planting strips into the sidewalks and streets of lower income neighborhoods of color. So decades of neglecting to plant trees in South Sacramento has created this community of people who suffer the highest temperatures, the worst air pollution and the most asthma. 

Kat Kerlin: She says people are less likely to plant trees where they live if they don't own their home or if they don't stay in a place long enough to literally put roots down. And landlords don't always want to deal with a maintenance or watering responsibility of trees. While residents don't always realize they have the right and resources to ask for them. 

Amy Quinton: I never knew that. I never knew that residents have the right to ask for trees. That's amazing. I wonder how the tree planting situation has changed since the pandemic. Since everyone is having to stay home more are more people getting trees for their yards or are they harder to come by? 

Kat Kerlin: I was curious about that, too. I talked with Victoria after the pandemic began to see how things were going. She mentioned something that's just one tiny example of how vulnerable communities stay vulnerable. She said that since COVID-19 came to town, there's been a surge in tree requests from more affluent communities where more people are likely working from home and have decided to improve their yards. But that's not the case in less affluent areas like South Sacramento. 

Victoria Vasquez: Most of the people who served in the past in South Sacramento are essential workers. They work in restaurants and daycare centers. They're struggling. So when these types of jobs are lost and they're wondering how am I going to feed my family? The last thing they're thinking as I'm going to plant a tree today. 

Amy Quinton: Yeah, that makes total sense. 

Kat Kerlin: This micro trend illuminates a much broader issue and is played out across several U.S. cities of how heat, health and racial disparities build on and exacerbate each other. 

Amy Quinton: And you looked at that in your last article, right? 

Kat Kerlin: Right. Victoria pointed out that many of the same communities affected by poverty and heat islands also have higher rates of COVID-19 in the city. These issues all intertwine. And if you layer city maps of COVID-19 cases, socioeconomically disadvantaged communities and tree canopy, the results are striking and sobering. 

Victoria Vasquez: You see so clearly that disadvantaged, unhealthy people don't have as many trees in their neighborhoods and they have higher, hotter temperatures. It's a perfect storm of environmental injustice. We've been predicting this for a long time and now it's playing out in the worst possible case scenario. Hopefully people will listen. 

Amy Quinton: Yeah. Last week's Unfold episode on coronavirus and climate change, we talked to Helene Margolis. She's with the UC Davis School of Medicine. And she basically agreed with Victoria. 

Helene Margolis: I think that what COVID-19 has done with the pandemic has done is really laid bare the disparities, the health disparities, the resource disparities, and the fact that in a sweeping event like this, everyone's potentially at risk in one way or another and that we need to build the resilience.

Amy Quinton: This all sounds pretty depressing, Kat. 

Kat Kerlin: I think it's also enlightening. So I talked to experts who say we really can't talk about climate change solutions without talking about racial injustice, especially in the United States. And more people are waking up to that.

Amy Quinton: But it's really hard to have a healthy community when so many vulnerable communities are under stress and strain.

Kat Kerlin: Exactly. So Adrienne Lawson is with our UC Davis Office of Health Equity, Diversity and Inclusion. She told me about a study from our nursing school that really stuck with her. It found that even well-educated, financially stable African American women can expect to be less healthy than poor white women.

Adrienne Lawson: As an African American woman, I'll feel pretty financially secure. I have a Ph.D. I have a great career, but the mental and physical toll that racism has on people is very detrimental to our health. If you don't have good health, nothing else matters. 

Kat Kerlin: You know, at first I optimistically called the final installment of Becoming Arizona "What Works?" But guess what? We don't have all the solutions. However, there are ideas being voiced by public health experts, climate scientists and community leaders and even being written into climate action plans that increasingly view these issues through the lens of a global pandemic and racial inequities. 

Amy Quinton: Well, I know in Sacramento, anyway, the Mayor's Commission on Climate Change weaves social equity throughout its new climate action plan, right alongside recommendations for sustainable land use, transportation and urban greening. 

Kat Kerlin: People are starting to recognize that trees, heating and cooling are social justice issues. 

Amy Quinton: Meanwhile, it's getting hotter and deadlier.

Kat Kerlin: Yeah. Maricopa County, where Phoenix sits, had 40 confirmed heat associated deaths as of late August this year with 270 more under investigation. 

Amy Quinton: And, you know, Sacramento had at least a seven-day heat wave this summer, but thankfully, no heat-related deaths so far this year.

Kat Kerlin: But you can't really manage what you don't measure. And we're just beginning to do that. Maricopa County was actually one of the first places in the nation to start tracking heat-related illness. By understanding the scope of the problem, they can improve their outreach efforts and maybe actually help people. 

Amy Quinton: If you want to dig in deeper, check out the Becoming Arizona series at 

Kat Kerlin: And you can hear more of our episodes at I'm Kat Kerlin. 

Amy Quinton: And I'm Amy Quinton. Thanks for listening. 

Credits: Unfold is a production of UC Davis. It's produced by Cody Drabble. Original music for Unfold comes from UC Davis alumnus Damian Verrett and Curtis Jerome Haynes.