Did you know that more than half the people in the world lives in cities? The hustle and bustle of a city can be awesome, but cities can also be hot and polluted. Luckily, there’s a solution we can all get behind – trees! Join Molly and co-host Nallini as they learn how these magnificent towering giants make our cities better places to live and help fight climate change. They’ll also visit an urban orchard that grows fruit in the middle of Philadelphia. All that plus a tree-mendous mystery sound!

Additional Resources:
If you want to learn more about the Philadelphia Orchard Project, visit phillyorchards.org.

Interested in volunteering in your city? Check out treesaregood.org.

Want to plant a tree of your own? Neighborhood Forest gives thousands of free trees to kids every year across North America. Learn more at neighborhoodforest.org.

Audio Transcript

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NALLINI: You're listening to Brains On, where we're serious about being curious.

CHILD: Brains On is supported in part by a grant from the National Science Foundation.

NALLINI: Molly, Molly. Where are you? Anyone seen a woman with glasses, brown, curly hair, and the voice of a charming podcast host? We plan to meet in our favorite park in the city.

MOLLY BLOOM: Psst! Nallini, I'm right here,

NALLINI: Molly! There you are. No wonder I didn't see you. You're hiding in the bushes.

MOLLY BLOOM: Yes. Come over here.

NALLINI: I'm coming. I'm coming. Ooh. I like your cargo jumpsuit, Molly. It has so many pockets.

MOLLY BLOOM: Thank you. They're full of emergency snacks, mostly loose craisins and blocks of sharp cheddar cheese. Cheese. Exactly what you need in emergencies.

NALLINI: Ooh. And are those binoculars?

MOLLY BLOOM: Yes, but, shh!

NALLINI: What are we doing hiding in the bushes?

MOLLY BLOOM: I'm tree watching. It's like bird watching, but for trees.

NALLINI: And we're whispering because why?

MOLLY BLOOM: Because I saw some cool birdwatchers whispering, and I figured all watchers probably whisper.

NALLINI: I don't think the trees will be scared if we talk normally.

MOLLY BLOOM: Huh. Good point. OK, hold on. Psssh. Woosh. Don't mind me. I'm doing my tree call. Holy moly. Is that a red mulberry?

NALLINI: You mean that giant tree in the middle of the park?

MOLLY BLOOM: Yes. My tree calls are getting really good.

NALLINI: But that tree has been there this entire time.

MOLLY BLOOM: I got to snap a pic for my blog Trees R US. #allaboutthattreelife, #treefluencers, #redmulberriesaremyfave.


You're listening to Brains On for APM Studios. I'm your host, Molly Bloom, and I'm here today with co-host Nallini from Los Altos, California. Welcome, Nallini.

NALLINI: Hi, Molly.

MOLLY BLOOM: You know, I'm still thinking about that mulberry tree. Trees are just so magnificent.

NALLINI: I agree. I love the sound of the wind through their leaves.

MOLLY BLOOM: Sometimes their bark is smooth, like a white birch tree.

NALLINI: Sometimes it's rough and bumpy, like a pine tree.

MOLLY BLOOM: Each leaf has its own unique design and feel, like oak leaves with their round edges and waxy texture.

NALLINI: Or the soft fan-shaped leaves of a ginkgo tree.

MOLLY BLOOM: Trees are truly something to wonder at. And, Nallini, today's episode was inspired by a question you had about them.

NALLINI: Yeah, I wanted to know, how do trees help cities?

MOLLY BLOOM: That is a tremendous question. So what made you think of it?

NALLINI: I guess I've always wondered, why there are so many trees in a certain part of the Bay Area where I live because I was in Washington DC at the time. And when I was there, there was trees, but not as much as where I'm from. There's the big hills in Rancho San Antonio that are covered in trees and wildlife. And well, it's just really green and it's beautiful, but so is Washington, DC, but not really-- plant life wise, there's not as many.

MOLLY BLOOM: So do you have a favorite kind of tree?

NALLINI: Yeah, I guess. I like Redwood and Sequoia trees. I have some of them in my backyard.


NALLINI: And they're like-- yeah. They're huge.

MOLLY BLOOM: Can you describe those?

NALLINI: They're really tall. It's like a red stem of a tree that leads all the way to the top. And then there's just leaves just spreading out, and it gets smaller and smaller as it goes up. And it's really similar to Sequoia trees, except, they're really, really tall.

MOLLY BLOOM: Have you ever hugged a tree before? I love to hug trees myself.

NALLINI: Yeah, it was really nice. I was at science camp. And we had something called an epic journey where you got to do a solo hike. And our field class leader, she would put cards down on a trail to where she was, where we would meet her. And on each card, there was something we'd had to do.

And one of the cards it said, hug this tree. And I did. It was really-- it felt nice. It was really bumpy for sure, but I liked it.

MOLLY BLOOM: Have you ever talked to a tree.

NALLINI: I think so. Maybe once or twice when I'm hiking with my parents or my friends. Just for fun, I'd say, hi, how are you doing? And then I would just wait like a couple of seconds. They're like, OK, have a nice day. And I would just do that continuously down the trail for fun.

MOLLY BLOOM: Oh, that makes me very happy. Trees are great listeners, it turns out.



MOLLY BLOOM: More than half of all people in the world live in cities, including me and Nallini. And cities can be great.

NALLINI: There are usually lots of cool places to visit.

MOLLY BLOOM: Like museums, or different restaurants, or fun shops like Marty Munster's Cheese Emporium. They have the best emergency cheese this side of the Mississippi River.

NALLINI: And the cities are filled with lots of different people.

MOLLY BLOOM: Yeah, there's a real hustle and bustle.

NALLINI: But there are some not so great things about cities too. There can be a lot of cars and traffic.

MOLLY BLOOM: And all those cars and trucks release pollution into the air. One of the biggest kinds of pollution in our air is called carbon dioxide.

NALLINI: Or CO2 for short.

MOLLY BLOOM: CO2 is one of the gases that's causing climate change today.

NALLINI: One of the main effects of climate change is that the Earth is getting warmer and warmer.

MOLLY BLOOM: That's happening because we're releasing lots of CO2 into the air. Once it's in the skies, it traps heat, and that causes the planet to warm up over time, almost like a big blanket.

NALLINI: CO2 is released into the air when us humans burn fossil fuels, like gasoline in our cars.

MOLLY BLOOM: But that's where trees can come to the rescue because trees are super.

CHILD: No doubt.

RUBY GUNTHRIE: Did somebody just say no doubt?

(SINGING) Because I'm just a tree

I'd rather be green

Because I do lots of growing at night

MOLLY BLOOM: It's Brains On producer Ruby Guthrie. Cool cargo pants, by the way.

RUBY GUNTHRIE: We totally match.

MOLLY BLOOM: They're the best.

RUBY GUNTHRIE: And Gwen Stefani approved. Yeah.

(SINGING) I'm just a tree

Yes, I got lots of leaves

All the better to photosynthesize

NALLINI: Wait, who's going to tell her she's not a tree?

MOLLY BLOOM: I think she knows.

RUBY GUNTHRIE: Don't worry, you two. I totally know I'm not a tree, but I really wish I was because trees are so cool. Almost as cool as whispering or xylophones.


NALLINI: Whoa. Did you just pull a xylophone out of your cargo pants?

RUBY GUNTHRIE: Maybe? Yes, definitely. What can I say? I love a good pocket.

MOLLY BLOOM: Wow. Those must be some deep pockets. But back to the trees. Nallini and I were just talking about how awesome they are.

RUBY GUNTHRIE: Trees are indeed awesome. Dare I say, iconic. Spoiler alert. I dare. But trees aren't just awesome to look at. They're also awesome helpers, like the dish sponges of the Earth.

They're great at cleaning up. Tell us more. Trees, like all plants, take in CO2 gas, including some of that CO2 that's causing climate change. And with the help of some sunlight and water, trees can turn that CO2 into oxygen.

MOLLY BLOOM: Oh, yeah. Plants breathe in CO2 and breathe out oxygen. And us humans love oxygen.

RUBY GUNTHRIE: Almost as much as we love ranch dressing, or whispering, or punctuating our sentences with little xylophone sounds. Like this.


NALLINI: OK, so plants take in CO2 and put out oxygen.

MOLLY BLOOM: Right. This process is called photosynthesis.

NALLINI: That's fun to say. Photosynthesis. Trees help clean our air Thanks to photosynthesis.

MOLLY BLOOM: Thanks trees. And thanks photosynthesis.


Trees also help clean up other types of pollution, even super tiny pollution particles, like microscopic bits of dust, dirt, and smoke that mix with the water in our air.

RUBY GUNTHRIE: Sounds like the worst kind of microscopic smoothie.

MOLLY BLOOM: Yes. Nobody wants a dirty, smoky pollution smoothie floating around in the air, but that's exactly what these tiny pollution particles are. But they come from all sorts of stuff, from construction to factories to cars.

NALLINI: So how do trees help?

MOLLY BLOOM: Tree branches and leaves catch these tiny pollution particles. Kind of like a lint roller. When it rains, those pollution particles wash off the leaves and drain into our sewers, which is much better than having all that pollution smoothie hanging out in the air for us to breathe in. We want our air and wind to be pollution free.

RUBY GUNTHRIE: Oh, speaking of wind. Ta-da.

NALLINI: Ruby, where did you get those wind chimes?

RUBY GUNTHRIE: Uh, my cargo pants, of course. They're like the Mary Poppins purse of pants. I even keep emergency fresh breezes in this pocket. Check it out.


NALLINI: What else do you have in there?

RUBY GUNTHRIE: Oh, the usual. My xylophone, mallets, keys, unopened mail, cherry lip balm, and, of course, emergency cheese.

NALLINI: I wish I had pockets for emergency cheese.

RUBY GUNTHRIE: Oh, wait a sec. I have just the thing. Aha! My emergency cargo vest. It's all yours, Nallini. And it has lots of cheese pockets.

NALLINI: Thanks, Ruby.

RUBY GUNTHRIE: Now we're all matching. Yes! And I have so much more to tell you about trees. Ah! My emergency wind is blowing away all my unopened mail. No! I never opened it. What if it's fan art? Be right back.

MOLLY BLOOM: We'll hear more from Ruby in a bit, I think. But first, I hope your ears are ready to branch out because it's time for the--


--mystery sound. Nallini, are you ready to hear the mystery sound?


MOLLY BLOOM: All right. Here it is.


What do you think?

NALLINI: I feel like I do now. It feels like something's dropping. And then maybe when you're cutting wood, you put it down on something. And then you bring the saw, and then you just kssh.


NALLINI: And then I used to do woodworking, and I used something similar to that. You would just put a piece of wood down, and you would just bring it. Put another one, bring it. It was like-- and I remember that noise.

MOLLY BLOOM: So those repetitive--

NALLINI: I feel like it's-- yeah, I feel like it's like that.

MOLLY BLOOM: OK, so we're thinking a woodworking tool, a saw potentially. Do you want to hear it again?




MOLLY BLOOM: What do you think now?

NALLINI: It sounds like a cymbal, on a drum set. But maybe you hit the cymbal and then there's another thing-- you just like, step on something, and it stops. And then you release it and then you go, pshh.

MOLLY BLOOM: OK, so maybe a drum set. It's a musical sound. Well, we'll hear it again. Get another chance to guess and hear the answer at the end of the show after the credits.

Here at Brains On, we love trees, drawing trees, hugging trees, even planting trees.

NALLINI: And we want to hear from you.

MOLLY BLOOM: Yes, listeners, please send us a photo or video of you hugging a tree or better yet, planting a tree.

NALLINI: Share your photos and videos at brainson.org/contact.

MOLLY BLOOM: While you're there, you can send us your mystery sounds, drawings, and questions.

NALLINI: Like this one-- why does our tongue stick to ice?

MOLLY BLOOM: You can find answers to questions like these on the Moments of Um podcast. Again, that's brainson.org.

NALLINI: So keep listening.

MARC SANCHEZ: Brains On Universe is a family of podcasts for kids and their adults. And since you're a fan of Brains on, we know you'll love the other shows in our universe. Come on, let's explore.

ROBOT: Entering Brains On universe. Whoa. So many podcasts.

Brains On. Smash Boom Best, Forever Ago. Oh, picking up signal. Forever Ago, a history podcast starring Joy Dolo.

JOY DOLO: Flare's gum was so sticky. When the bubble popped, it was so hard to get off your skin. You'd have to scrub it off with harsh chemicals.

ROBOT: Me love sticky facts. Zorp! Signal down. Quick! Need Forever Ago now.

MARC SANCHEZ: Search for Forever Ago wherever you get your podcasts.

Ba, ba, ba, ba, ba, Brains On.

NALLINI: You're listening to Brains On. I'm Nallini.

MOLLY BLOOM: I'm Mollie.

RUBY GUNTHRIE: And I'm Ruby. And don't worry, I got my mail. It was just a letter from a distant cousin saying we inherited definitely not haunted castle. Hmm. No biggie. I also found this triangle.


Ring a ding, ding indeed. Anyway, today we're talking about trees.

NALLINI: And how they help our cities.

MOLLY BLOOM: Before the break, we learned that cities are great, but they can be full of pollution. Luckily, trees help clean our air.

NALLINI: Their branches trap tiny bits of pollution, and they suck up carbon dioxide and turn it into oxygen.

MOLLY BLOOM: Correct. And they also soak up water during storms. OK. Picture a big storm.




NALLINI: I'm picturing it. It's like it's raining cats and dogs.

MOLLY BLOOM: Absolutely bucketing. When it storms, trees act kind of like an umbrella, using their leaves and trunks to slow the water down and keep the ground from flooding too quickly. Their roots are also great at soaking up water like a straw.


And roots also help hold the ground together, which keeps the soil from washing away.

NALLINI: Wow. So trees can really protect us from these big storms.



Trees also create shade, which cools down the air and land around them. Some studies show that cities with trees are almost 3 degrees cooler than cities without.

NALLINI: Trees are just so cool.

MOLLY BLOOM: Literally.


And Thanks ruby, for punctuating our sentences with these triangle dings. Really makes it sound like what we're saying is special.

RUBY GUNTHRIE: Oh, of course. All of my hours of triangle practice are really paying off. So to recap. Trees can help protect us from storms, cool us with shade, and they help take pollution out of the air.


But there's even more. Trees are also good for our mental health.

NALLINI: They're good for our brains?

RUBY GUNTHRIE: Yep research shows that spending time around trees or even just looking at them can help us feel less stressed.


Thanks, trees.


Oops, sorry. I got a little carried away with the triangle there. Back in my pocket it goes.

MOLLY BLOOM: Nallini, now that you've heard how trees help cities, what do you think? Anything surprise you?

NALLINI: It surprised me that trees' branches trap tiny bits of pollution, and then they suck in the carbon dioxide. And then let out the oxygen that we breathe. So it's a win-win.

MOLLY BLOOM: Totally. So cool. Trees, what can't you do? Well, apparently they're really bad at returning my calls, but hey, nobody's perfect.


Oh, my gosh. Is that Willow?

NALLINI: Alternative indie pop star Willow Smith is here?

MOLLY BLOOM: I love her Tiny Desk Concert.

RUBY GUNTHRIE: No, willow tree. I'm, like, such a huge fan. I have to get an autograph. Got a blast. Willow! Willow!

NALLINI: Bye, Ruby.

MOLLY BLOOM: Trees do so many things for us and our cities.

NALLINI: But there's another thing that trees do. They can grow food.

MOLLY BLOOM: Yes. To learn more, we talk to Sharon Appiah.

NALLINI: They're the Orchard director at the Philadelphia Orchard project, which runs nearly 70 orchards in the city.

MOLLY BLOOM: An Orchard is sort of like a farm, but only for trees. Imagine a plot of land with rows and rows of trees right in the middle of a busy, bustling city.

NALLINI: Right. And fruit trees can be really helpful for cities because they provide fresh food to the people that live there.

MOLLY BLOOM: All of the fruit grown through the project is given to the community for free. Sharon usually works at an Orchard in West Philadelphia. It's a big, bountiful green space right next to one of the neighborhood's main streets.

NALLINI: You can hear all kinds of sounds in the Orchard, like birds and bugs, but also clanging trolleys and joggers going by.

SHARON APPIAH: My name is Sharon Appiah, and I am the Orchard director with the Philadelphia Orchard Project. This is the learning orchard, which is right in West Philly. It is an example of over 90 fruit and nut trees, over 100 berries and Bramble. Sometimes we do a mix of common fruit that people are familiar with.

So we'll plant apple trees, plum trees, cherry trees, peaches, apricots. This is fruit that you'll normally see at the grocery store. And I find that is a great way to draw people in because these are the fruits that people are familiar with.

I believe fruit trees give us so much beauty. They are a way to draw in the community. I think fruit trees are a really cool way-- If you're not someone who's established a relationship with plants or nature, it's a really good start because they change so much and so much about being in relationship with people or things is about sticking around to see how they change. And then they also change you too. And that's beautiful.

My hopes for the future are that we are able to plant more fruit trees because I like to walk, and I ride the public transportation as I see all these empty lots that are filled with trash or they're just empty and abandoned. And if my biggest, wildest dream could come true, every single lot in the city would have fruit trees.

MOLLY BLOOM: Nallini, have you ever noticed any fruit or nut trees in your neighborhood?

NALLINI: Yeah, I actually have. There's a person who lives down the road. They have a big orange tree. And sometimes I see a squirrel almost every other day, just climbs up like this kind of staircase thing that they have and just plucks one and then takes it and leaves. But usually, it leaves like a big dent in it and just doesn't eat the rest.

MOLLY BLOOM: So what kind of fruit would you like to grow in your neighborhood if you could add some more fruit trees?

NALLINI: I really love plums. And I think they're in season right now, so that would be great. I love strawberries, blueberries, blackberries, apples, cherries, grapes, oranges. I love everything.

MOLLY BLOOM: We need to get you some fruit trees. It would be great if all of our neighborhoods were filled with all kinds of trees. Unfortunately, some cities don't have as many trees as other cities. And even in a city full of trees, there might be some neighborhoods with a lot of them and others that hardly have any.

NALLINI: Yeah. Some people might step outside of their apartment or house, and there's only one or two trees on their entire block. So little green, so little shade.

MOLLY BLOOM: While other people walk out their front door, and there's an entire park filled with trees.

NALLINI: Usually, the places with more trees are the same, places where people have more money.

MOLLY BLOOM: Neighborhoods of people with less money usually have fewer trees, which means those people have to deal with more pollution and more heat.

NALLINI: And leads to more problems for the people that live there.

MOLLY BLOOM: They may have to worry more about keeping cool when it's hot out because using air conditioning can be expensive. Plus, air pollution can be really hard on your body, especially your lungs.

NALLINI: It's not fair that some neighborhoods have more trees while others don't.

MOLLY BLOOM: Absolutely. But there are organizations like the Philadelphia Orchard Project and others that are working on making more green spaces for everyone.

NALLINI: Yeah, and a lot of them need volunteers to help plant trees, which seems like a nice thing to do for a tree, considering how much they do for us.

MOLLY BLOOM: If you want to get involved in planting trees in your city, we have resources in our show notes.

NALLINI: Molly, I have an idea. What if we planted a tree right now?

MOLLY BLOOM: I love that idea. Can it be a red mulberry?

NALLINI: Definitely.

MOLLY BLOOM: Let's go.


Over half of the world's population lives in cities, and trees help make our cities better.

NALLINI: Trees use their branches and leaves to filter out pollution in our air.

MOLLY BLOOM: They also turn carbon dioxide into oxygen through photosynthesis.

NALLINI: Trees provide shade and sometimes even food, like cherries.

MOLLY BLOOM: Some neighborhoods have fewer trees than others.

NALLINI: But there are lots of folks working on creating green spaces in every neighborhood.

MOLLY BLOOM: That's it for this episode of Brains On.

NALLINI: This episode was written by--

MOLLY BLOOM: Ruby Guthrie.

NALLINI: And produced by--

MOLLY BLOOM: Molly Bloom.



NALLINI: Our editors are--

SANDEN TOTTEN: Sanden Totten.


SHAHLA FARZAN: Shahla Farzan.

NALLINI: Fact checking by--

KATIE RUTHER: Katie Ruther.

MOLLY BLOOM: We had engineering help from Steven Glaze and Josh Savageau. The sound design by--

RACHEL BREES: Rachel Brees.

MOLLY BLOOM: Original theme music by--

MARC SANCHEZ: Marc Sanchez.

NALLINI: We had production help from the rest of the Brains On universe team.

ANNA GOLDFIELD: Anna Goldfield.

NICO GONZALEZ WISLER: Nico Gonzalez Wisler.

LAUREN HUMPERT: Lauren Humpert.

JOSHUA RAY: Joshua Ray.

MARK SANCHEZ: Mark Sanchez.

CHARLOTTE TRAVER: Charlotte Traver.

ANNA WEGGEL: Anna Weggel.


ARON WELDESELASSIE: Aron Woldeselassie.

MOLLY BLOOM: Beth Perlman is our executive producer and the executives in charge of APM Studios are Chandra Kavati and Joanne Griffith. Special thanks to Vasudevan Krishnamurthy and Vidya Raman.

NALLINI: Brains On is a non-profit public radio program.

MOLLY BLOOM: There are lots of ways to support the show. Subscribe to Brains On Universe on YouTube, where you can watch animated versions of some of your favorite episodes or head to brainson.org.

NALLINI: While you're there, you can send us mystery sounds, drawings, and questions.

MOLLY BLOOM: Nallini, are you ready to listen to that mystery sound again?

NALLINI: Of course.

MOLLY BLOOM: Here it is.


All right. What do you think now?

NALLINI: I still think the same. It's like a woodworking machine. You bring the piece of wood. It chops it. Then you bring it out, and you bring the blade up. And you put a new piece of wood, and it just keeps going back and forth like that.

MOLLY BLOOM: So someone is cutting a bunch of pieces of wood, you think?

NALLINI: Yes, basically. With an actual contraption, not with their bare hand or anything.

MOLLY BLOOM: Love it. All right. You ready for the answer?


MOLLY BLOOM: Here it is.

YUBA: My name is Yuba. I live in Nevada City, California. That was the sound of me pumping up my soccer ball. I chose that sound because I liked the rhythm of it.

NALLINI: I did not expect that.

MOLLY BLOOM: So you did have it right that there was a rhythm. That's why Yuba liked it. But it's inflating a soccer ball. Have you inflated a soccer ball before?

NALLINI: Yes, multiple times. I play on a soccer team and sometimes my coach, she forgets to fill up the soccer ball. So he just has some of us do it.

I don't remember it sounding like that, but maybe it's like a different machine.

MOLLY BLOOM: Yeah. Or maybe next time you got to listen to it. Is it a hand pump you use or is it like--

NALLINI: Yeah. You just put the needle into the hole and then you just go, one, two. Probably because I'm not like really paying attention to the noise, but when my coach is saying so like, I can pay attention.

MOLLY BLOOM: That makes sense. All right. You got to have to listen for that next time.



MOLLY BLOOM: Now it's time for the Brains Honor Roll. These are the incredible kids who keep the show going with their questions, ideas, mystery sounds, drawings, and high fives.



This is the last episode of the season, but we'll be back in a few months with brand new episodes. In the meantime, please send us your questions, fan art, and mystery sounds to brainson.org/contact.

NALLINI: Thanks for listening.

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