Episode 1: Cooling cities by throwing shade

Fewer trees shade the poor neighborhoods of U.S. cities, but increasing the urban canopy involves more than just adding trees.

The lack of shade is apparent for people waiting in line for unemployment payment at this Bank of America branch in Boyle Heights.
Photograph by Elliot Ross

Trees provide much-needed shade for urban Americans on a hot day, but not everyone gets to enjoy it. New research illuminates how decades of U.S. housing policy created cities where prosperous, white neighborhoods are more likely to be lush, and low-income communities of color have little respite from the sun. National Geographic writer Alejandra Borunda explains how activists are trying to make Los Angeles greener and healthier for everyone, and why the solution isn’t just to plant more trees.


ELI CHEN (HOST): It’s summer in Los Angeles. So it’s hot, a little breezy, and every now and then you’ll catch the tune of a roving ice cream truck.

EILEEN GARCIA (ENVIRONMENTALIST): I’m just recording the sounds of my neighborhood here.

CHEN: In the Huntington Park neighborhood, you might see a woman named Eileen Garcia driving from tree to tree, trying to give them some much needed relief from the heat. 

GARCIA: So my first tree I’m stopping at is a crape myrtle. It was planted about six months ago as a replacement tree, and it’s drying out. It’s gotten scorched by the heat wave that just passed.

CHEN: Eileen parks next to the tree, then heads to the back of her truck, where she’s got a 300-gallon water tank with a hose. 

(Sound of pouring water)

GARCIA: My top priority for this particular tree, since it’s so scorched, is getting the 15 gallons of water into it, which is basically about three buckets’ worth, and putting down a layer of mulch to protect it from that rapid evaporation.

(Sound of shaking leaves)

CHEN: This is a part of Eileen’s job. She’s the regional manager in southeast L.A. for TreePeople, an environmental nonprofit that aims to plant more trees in the city. In recent years, TreePeople has been planting trees in areas like Huntington Park that historically haven’t had a lot of trees compared to other parts of the city. Research shows that urban neighborhoods impacted by redlining—or, racist housing policies in the 20th century—have far less shade compared to more wealthy, predominantly white neighborhoods. 

GARCIA: It's hot. It's mostly cement. A lot of the homes are built pre-1950s. So that means there isn't air conditioning—because it's a lower income communities. 

CHEN: Less shade means less relief from hot summer days, which are only going to increase due to climate change. But the solution isn’t to plant more trees. Tree care can be expensive, time consuming, and require a ton of communication with the local community. Eileen stops at another tree, a gold medallion that’s easily identified by its big yellow flowers. 

GARCIA: I see that this tree has had the stake removed for whatever reason. Sometimes they just break and residents remove them. So what we try to do is make sure that we put these stakes back, so that way the tree will grow nice and straight, and it’ll give it that reinforcement. 

CHEN: She gets out some tools and starts hammering the stake back in. 

(Sound of hammer pounding nail)

GARCIA: And there we have it. Nice and straight. So beautiful—this canopy is absolutely gorgeous. These vibrant yellow flowers against the blue sky is just phenomenal.

CHEN: She’s here to help take care of the trees so that everyone can enjoy them, including her neighbors.

GARCIA: This is where I live, you know. So it became very, very near and dear to me to want to really support our efforts to increase tree canopy in regions that don't have them.

CHEN: I’m Eli Chen, senior podcast editor at National Geographic. And this is Overheard, a show where we eavesdrop on the wild conversations we have here at Nat Geo and follow them to the edges of our big, weird, beautiful world.

This week: Everyone needs trees, but not everyone gets to have them. We’ll explore the hidden history that made shade unavailable to many communities of color, why planting trees is more complicated than you’d think, and how to expand the canopy as the planet continues to heat up. 

More after the break.  

So how does someone end up as a tree person? For Eileen Garcia, it started when she was a little kid. She grew up with her grandparents in a neighborhood in L.A. called La Puente.

GARCIA: They're from Mexico, and they brought with them a lot of their planting trees. We had a lot of fruit trees growing up, and I grew up climbing them.

CHEN: Eileen says La Puente didn’t have many trees. But her grandmother would tell her stories about growing up in an adobe house along a canal, where her family grew their own food.

GARCIA: My grandparents were agricultural migrant workers. And I think it was very natural for them to exercise their skill sets in their home, the house where I would eventually be raised.

CHEN: So Eileen’s yard was lush with avocado trees and peach trees. There were also orchid trees with bright pink flowers. She says she treated them like her own private monkey bars. Eileen thought that was just normal. 

GARCIA: I don't think it really dawned on me that my house was so special until I started kindergarten. And when we were walking home from school, one of the little kids was like, Whoa, you live in the jungle house?

CHEN: Many people think of L.A. as a desert, not a jungle. But trees have a long history in Los Angeles. Oak woodlands grow naturally in L.A. And before Europeans arrived, the Indigenous Tongva people managed the woodlands and lived off the acorns. But these days, when most people picture L.A., they don’t think of shade.

ALEJANDRA BORUNDA [NATIONAL GEOGRAPHIC REPORTER]: L.A. as a city is based around and built around sunshine. 

CHEN: This is Alejandra Borunda. She’s a writer at Nat Geo’s environment desk. And she wrote a cover story about the lack of shade in L.A.  

BORUNDA: That's why people came here. That's why Hollywood loves this place. The quality of the light is exceptional. The sunshine is exceptional. It's a beautiful place if you love sun.

CHEN: But even for people who love sunshine, there’s a darker side to the sun. And it’s a problem all over the U.S.—not just Los Angeles. Cities tend to be warmer than surrounding areas because asphalt and building materials trap heat. On top of that, heat waves fueled by climate change can make cities unbearable.

BORUNDA: So heat stress is actually the most deadly kind of natural disaster that we have in the U.S. Heat stress kills more people every year than any other kind of natural disaster, on average. It's a really big deal.

CHEN: This summer, we’re seeing just how bad extreme heat can be. Take the Pacific Northwest. Washington, Oregon, and Canada aren’t places where you’d expect to fry an egg on the sidewalk. But in June, Portland reached 116 degrees—the highest temperature ever recorded there. Health officials say the heat led to hundreds of deaths. And Alejandra says that there might be days in our future when we can’t get a break from the heat, even when the sun goes down. 

BORUNDA: Like it's not just the extreme temperatures at two o'clock on an afternoon, it's this extended period of heat. It's like when the heat lasts for a couple of days and when it doesn't cool down again at night.  

CHEN: And with climate change, the heat is only going to get worse. But there is a bit of good news. There’s a simple tool that helps keep our cities more pleasant. 

VIVEK SHANDAS [ECOLOGIST]: Trees are one of those unusually curious features of an urban landscape.

CHEN: Vivek Shandas is an urban ecologist at Portland State University. In cities, trees compete for space with roads and buildings. Unlike asphalt and building materials, which trap heat, Shandas says trees do all kinds of things to make life better. 

SHANDAS: They're like the little workhorses or lungs of the neighborhood that you often might not even anticipate. But they're working 24/7 for you. 

CHEN: So just some science 101: Leaves give us shade, which cools us down, and trees recycle carbon dioxide into oxygen, which makes the air fresher. But there are other, unseen ways that trees regulate heat. For one, they’re constantly pulling water out of the ground. And when the temperature goes up, that moisture transpires off the leaves into the air.   

SHANDAS: And so what you're actually experiencing on a hot day is that little bit more moisture in the air absorbs some of that heat. And actually you might feel a little bit cooler as you walk by that tree—not only because of the shade, though also because of that shift in the amount of moisture in the air around that tree.

CHEN: These benefits add up. Neighborhoods with lots of tree cover can be 15 or even 20 degrees cooler than areas without shade. 

SHANDAS: And that really matters because if we're talking about a hundred-degree day, one neighborhood could be much lower temperature and one neighborhood could be much higher temperature as a result of the presence of our green leafy friends.

CHEN: So having more trees can make heat waves less deadly. And trees can also lead to lower energy costs because air conditioners don’t have to work as hard. But the thing about trees is that they’re expensive. Money may not grow on trees, but as one researcher puts it, trees grow on money. So that creates a divide between who gets shade and who doesn’t.

Alejandra wanted to see this divide for herself, so she traced the path of one street in Los Angeles: Vermont Avenue. She started in South Central L.A., in a neighborhood called Pico-Union, which isn’t far from Huntington Park. More than half the residents there are Hispanic or Latino. And tree coverage here is sparse.   

BORUNDA: You could look up and only a few percent of the sky above you would be covered by any kind of tree canopy.  

CHEN: That means on a hot day, there’s almost no shelter from the sun. 

BORUNDA: I talked with some women who remembered trees that had previously existed next to their bus stops that got taken out. And now they were standing, you know, trying to find the little bits of shade—usually behind a telephone pole—to keep themselves cool while they waited for their buses. 

CHEN: But as Alejandra drove north, the scenery changed. Six miles away from South Central L.A., she was still on Vermont Avenue and still in the heart of the city. But the streets had grown greener. 

BORUNDA: And when we ended up all the way up in Los Feliz, one of these really beautiful, old, leafy neighborhoods, you basically couldn't see the sky above you. 

CHEN: Here, the canopy covered more than 40 percent of the sky. There was plenty of refuge on a hot day. And people who live in this neighborhood tend to be much more prosperous—and much whiter—than those a few miles down the street.

BORUNDA: And wealthier, often whiter areas that have had a lot more city-led investment over the years tend to have a lot more trees. 

CHEN: In L.A., it’s a stark difference. Nearly a fifth of the city’s trees are located in just five census blocks, where just one percent of L.A.’s population lives. 

But this shady divide? It’s no coincidence. To understand why shade became a luxury in the first place—and why some communities struggle to plant trees today—you have to go back to one series of maps created more than 80 years ago. 

We’ll explain after this. 

There’s a hidden history that explains why some urban neighborhoods are so leafy you can barely see the sky above you and others have almost no shade. It all starts with a subject that seems to have nothing to do with trees: home mortgages and the worst economic crisis in American history.  

SHANDAS: During the 1930s, we’re coming out of the Great Depression.

This is urban ecologist Vivek Shandas again. So at the depth of the Depression, Franklin Roosevelt is elected president.

FRANKLIN DELANO ROOSEVELT: ...that the only thing we have to fear is fear itself. 

CHEN: And launches the huge economic program we know as the New Deal. Shandas says one of the many problems FDR had to fix was homeownership.  

SHANDAS: A lot of people were defaulting on their mortgages, a lot of concern around the ability for homeowners to actually stay in their homes.

CHEN: So the government stepped in. Roosevelt created a federal agency called the Home Owners’ Loan Corporation. It was designed to give people better access to home loans. The HOLC started off by appraising neighborhoods in more than 150 cities. They made maps that graded residential areas. 

SHANDAS: The maps that would tell the Home Owners' Loan Corporation in a specific city which areas were “the best” for investment and these home mortgages, which areas were the riskiest for putting these home mortgages.

CHEN: So the “best” neighborhoods got As. B meant “still desirable.” C for “definitely declining.” And the lowest grade, D, went to neighborhoods considered “hazardous.” Assessors drew red lines around D-graded neighborhoods to make it really clear: these are the bad neighborhoods. 

But in cities all across the country, there were issues with how the government arrived at those grades. In the 1930s, Jim Crow segregation was legal. And even in northern cities, there were all kinds of tactics to keep Black people and other people of color out of white neighborhoods. And when the HOLC handed out grades, it considered white neighborhoods to be safer investments, simply because white people lived there.

SHANDAS: And risk in that sense was often decided by the local communities in and around these cities where there were immigrant communities, African American communities, people of color more generally, and then low-income communities.

CHEN: Even though redlining officially ended in 1968, it left a lasting mark. Individual people of color had a harder time buying houses, which had major economic consequences. 

And over time, cities were less likely to invest in C- or D-graded neighborhoods. 

SHANDAS: Parks weren't being sited in those locations—green spaces, trees. And often these large-scale industrial facilities or roadways were what were finding their way into those locations.

CHEN: Vivek Shandas has compared modern temperature measurements with maps of redlined neighborhoods. He’s shown that even today, all over the U.S., formerly redlined neighborhoods tend to be hotter and have fewer trees than areas that were graded A or B. 

SHANDAS: The quality of neighborhood that has been affected by some of these policies is a real spiral that gets communities into intergenerational poverty. Not because of any fault of their own, though—just because they were born into a neighborhood or a zip code that didn't get investment over time.

CHEN: And it’s not just this lack of trees. That’s only one consequence of decades of housing discrimination. Shandas says it will take a lot of work to acknowledge those disparities. And correcting them? That’s a huge problem that cities are tackling in different ways. 

REBECCA HANKINS (HORTICULTURIST): Um, do you want to stand in the shade?

CHEN: (Laughs)

HANKINS: More reason we need trees!

CHEN: (To Hankins) So yeah, I’m noticing there’s not, like, a lot of shade in this park. 

HANKINS: Right. Yes. 

CHEN: I don’t live in L.A. But I do live in a city that also suffers from tree inequity: St. Louis. So I met up with Rebecca Hankins in the Carr Square neighborhood in North St. Louis, a predominantly Black area of the city. Rebecca is the partnerships coordinator of Forest ReLeaf, a nonprofit tree nursery. And she’s showing me DeSoto Park, where the group wants to plant more trees. 

HANKINS: So what we're seeing is some soccer fields and really no tree coverage at all. I mean, you've got a few park benches, which may be used by spectators, but very few are in shade at all. I think just one. And if you can see it's being used right now by two people.  

CHEN: DeSoto Park is basically one big rectangle that’s got some fairly large trees along the perimeter. But they’re not large or close enough to the sidewalk to give people any shade. I point at a line of about a dozen younger looking trees, and Rebecca says those were planted by Forest ReLeaf about four years ago. 

HANKINS: So we came in, we put the trees in the ground, but nobody came and watered or maintained the trees. And we're finding that with tree plantings, especially in areas that have been underserved, you can't just come in, put in some trees, and hope that they're going to do well. These communities are struggling with other needs, and trees definitely fall to the bottom of the list. 

CHEN: DeSoto Park is right next to a few schools and a church, so Rebecca plans on reaching out to them to help address this issue. But also, residents in North St. Louis tend to have lower incomes compared to other parts of the metro area. Rebecca says a lot of people there can’t afford to prune and remove old, dying trees. And if the trees are on private property, the city can’t touch them. So the residents get stuck with trees that are a burden on their lives. 

HANKINS: But you'd be surprised. 

CHEN: (to Hankins) Yeah. 

HANKINS: How much people have opinion about a tree because they've had such a bad experience with a tree. And so trees on private property, for instance, that are dying and they don't have the money to remove those trees, then that tree has become a liability, and they're just frustrated with that tree and they can't see the benefit.

CHEN: Forest ReLeaf recently received funding to help people with tree upkeep and removal. And that could help people have a more positive experience with trees. 

HANKINS: Because the better people feel about trees, the more likely they are to embrace them.

CHEN: Rebecca says that in her circles, people have been talking about tree equity for years. But after the summer of 2020, there’s been a huge surge of interest from local companies and community groups to help plant more trees in North St. Louis. 

HANKINS: We've had a real wake-up call after the death of George Floyd. A lot of people are beginning to have these conversations, are beginning to look at this and understand that this is a real problem and that, you know, we have to do a little bit more to help communities that have been traumatized in the past. 

CHEN: But that still leaves a big unanswered question: Who’s going to pony up to fix it? Nat Geo’s Alejandra Borunda says there’s no easy answer. 

BORUNDA: This is a problem that has had such deep roots. Like it goes back so long and so far that, yeah, this question of whose responsibility it is to fix it is a really big and important one.

CHEN: Back in Los Angeles, the city has a goal of planting 90,000 more trees by the end of 2021, and increasing canopy cover by 50 percent in neglected neighborhoods by 2028. Since it’ll take a while for trees to grow large enough to provide shade, the city is also working on ways to redesign bus shelters and other infrastructure to provide more shade in the meantime. 

That’s a bigger commitment than many local governments have made. But even with that plan, a lot of the work still falls to individuals and groups like TreePeople. 

BORUNDA: And I think that's one of the big questions right now is, like, how cities can help them, how cities can support them, and what role cities should actually take to solve the problem themselves, rather than kind of passing the buck to these nonprofits that are doing really amazing work. 

CHEN: At the end of the day, according to Alejandra, a lot of change comes from people who live with the effects of redlining and just want to make their neighborhoods better.

After all, that’s how Eileen Garcia got started. In Huntington Park, TreePeople has planted a total of 1,400 trees.

GARCIA: We have some crape myrtles that are flowering beautiful purple buds. We have a Hong Kong orchid next to that that we planted. It’s not currently flowering, but the canopy is phenomenal, absolutely beautiful.

CHEN: And Eileen says residents have noticed a difference—especially the abuelas in her neighborhood. 

GARCIA: I was planting a couple of trees in front of a parkway. And this elderly woman came out and she's like—she's telling me in Spanish, “Put pretty trees.” And I was like, OK. So we brought our truck. We had several flowering trees. And I was like, Do you want yellow flowers or pink flowers? Or you know, there were crape myrtles. And she basically got to select her tree. She selected the lemon bottlebrush and a crape myrtle, which gave two different colors. So then she was standing under a bougainvillea, and she went into telling me that her father had planted that tree and how she'd watched it grow. And just watching her light up was so beautiful. And then she stood with me as I planted the trees and she said, I'm going to take care of them. I'm going to give them water. Don't worry about it, you know. And it just brought me so much joy to bring trees that she got to select, you know, and share that memory with her. 

CHEN: And that’s the kind of connection that can make our world a little bit shadier for everyone. 

Check out our show notes for more stories about trees, cities, and the people fighting for environmental justice. We have a link to Alejandra Borunda’s Nat Geo cover story, called “Los Angeles confronts its shady divide.” We also have a video that breaks down those redlining maps from the 1930s. 

And if you’re wondering why cities seem to be hotter than rural areas, it’s because they are. Check out our explainer of the urban heat island effect. And learn how urban parks could be a simple tool to mitigate some effects of climate change. That’s all in the show notes, right there in your podcast app. And don’t forget to rate us and review us wherever you listen. It’s a really big help. 


Overheard at National Geographic is produced by Jacob Pinter, Ilana Strauss, Brian Gutierrez, and Laura Sim.

Also, thanks to producer Milaena Hamilton, who recorded the interview with Vivek Shandas for an episode of the Nat Geo Explores video series.

Our senior producer is Carla Wills. Our Executive producer of audio is Davar Ardalan. Our fact-checkers are Robin Palmer and Julie Beer. Our copy editor is Amy Kolczak. This episode was sound-designed and engineered by Ted Woods. 

This podcast is a production of National Geographic Partners. Whitney Johnson is the director of visuals and immersive experiences. Susan Goldberg is National Geographic’s editorial director. 

And I’m your host, Eli Chen. Thanks for listening, and see you all next time. 


Want more?

Research shows how racist housing practices created oppressively hot neighborhoods. The video series Nat Geo Explores breaks down redlining and the lasting environmental impact of a series of 1930s maps

Black and brown communities bear the brunt of environmental degradation, pollution, and extreme weather fueled by climate change. After decades of activism, the environmental justice movement sees an opening to fix long-standing wrongs.

Also explore:

Why does shade matter? The urban heat island effect means cities are noticeably warmer than nearby rural areas. Even as the climate crisis will make urban heat more intense, parks and trees could help cities stay cool

An interactive map from the University of Richmond shows the discrimination baked into Great Depression-era federal housing policy.

For paid subscribers:

A National Geographic cover story explores Los Angeles as the city confronts its shady divide. Plus, driving down one L.A. street illustrates the legacy of decades of discrimination. 

If you like what you hear and want to support more content like this, please consider a National Geographic subscription. Go to natgeo.com/explore to subscribe today.