Roger: 0:02

Talking Trees with Lillian Jad. Welcome to Talking Trees. In this episode, we're exploring Santamore's 10-20-30 rule, a cornerstone of urban forestry that promotes diversity in city tree populations. This strategy helps mitigate the risk of widespread losses caused by pests and diseases. We'll discuss the rule's benefits, limitations and adaptability to various climates and urban scales, highlighting the critical role of biodiversity in creating resilient urban forests. Stay tuned as we unpack this foundational concept and its implications for urban forestry.

Jad: 0:44

Hey everyone and welcome back for another Deep dive. Today we're going to look at something you might not realize is super important to planning out our cities.

Roger: 0:53

Okay.

Jad: 0:53

So we're going to be talking about this idea of the 10-20-30 rule for planting diverse trees in cities.

Lilly: 1:00

I like it.

Jad: 1:01

So you probably already know that, like, diverse ecosystems are healthier, right. But this rule it kind of goes a little deeper. It shows how these seemingly simple numbers can actually protect our cities.

Lilly: 1:13

Interesting.

Jad: 1:14

Yeah. So to help us break all this down, we've got a YouTuber who's got some pretty strong opinions about the 10-20-30 rule Interesting. And then we also have a couple of articles that get into the science behind it, and you know all the debate around it.

Lilly: 1:28

I see.

Jad: 1:29

So, to get us started, why don't you explain, like, what is the 10-20-30 rule?

Lilly: 1:35

Yeah, absolutely so. At its most basic, the 10-20-30 rule says that no more than 10% of an urban forest should be any one species says that no more than 10% of an urban forest should be any one species, no more than 20% any one genus Got it and no more than 30% any one family.

Jad: 1:52

So it's like it's getting broader each time.

Lilly: 1:54

Exactly it starts with species and then expands to the genus and then the family level.

Jad: 2:00

And when I first heard about this rule, I thought this was like some age old wisdom passed down.

Lilly: 2:06

From generation to generation, yeah, from like you know the ancient arborists. Yeah, yeah, totally.

Jad: 2:11

But it's surprisingly recent. It is yeah, it was first mentioned by a guy named Dr Frank Santamore in 1990. Wow, and get this. Not even in a research paper, it was during a conference speech. A conference speech, huh, yeah. So even in a research paper, it was during a conference speech A conference speech huh. Yeah, so it's kind of interesting how-.

Lilly: 2:26

It's fascinating.

Jad: 2:27

It's become so widely accepted since then.

Lilly: 2:30

It really is. It's almost like a grassroots movement for trees.

Jad: 2:33

Yeah, it's like all these foresters just talking to each other.

Lilly: 2:38

Exactly yeah. Word of mouth.

Jad: 2:39

Yeah, exactly.

Lilly: 2:39

That's taken off.

Jad: 2:40

And it makes sense like, at its core, the 10, 20, 30 rule is all about resilience.

Roger: 2:45

Yeah.

Jad: 2:45

It's that old saying don't put all your eggs in one basket.

Lilly: 2:49

Right, exactly.

Jad: 2:50

Right, but instead of, you know, just talking about the basic ideas of monoculture and pests.

Lilly: 2:55

Right, which I'm sure a lot of our listeners already know about.

Jad: 2:58

Which you're probably already familiar with.

Lilly: 2:59

Yeah.

Jad: 3:00

Let's get into some of like the deeper arguments about this. I know one of the criticisms is that it might not actually be strict enough.

Lilly: 3:10

Yeah, that's a good point.

Jad: 3:11

Like you think about diseases like the ash borer right Right, which can wipe out entire genera of trees.

Lilly: 3:18

Exactly, it's not just one species.

Jad: 3:20

And that makes me think about this article I read that mentioned Amsterdam, the city center. It's something like 47% Dutch elm.

Lilly: 3:30

Wow.

Jad: 3:31

Like. Imagine walking down the streets there, surrounded by these huge, beautiful elms, but then realizing that almost half of them are the same species.

Lilly: 3:42

Oh, that's a scary thought.

Jad: 3:44

Yeah, and they're all vulnerable, they're all susceptible.

Lilly: 3:45

To the same disease.

Jad: 3:46

Oh, that's a scary thought, yeah, and they're all vulnerable, they're all susceptible To the same disease Exactly.

Lilly: 3:48

It's a huge risk.

Jad: 3:49

It could be catastrophic.

Lilly: 3:50

It really could yeah.

Jad: 3:51

And you know some experts are saying we need even stricter guidelines, like the 5-10-20 rule, the 5-10-20. Yeah, have you heard about that one?

Lilly: 3:59

I have yeah.

Jad: 4:00

It's kind of the same idea.

Lilly: 4:02

Yeah, it's the same concept, but even more stringent.

Jad: 4:04

Yeah, but I'm just thinking like, won't that like really limit our options?

Lilly: 4:15

That's a valid concern, especially in places where it's already hard to grow trees, exactly Like in harsh climates or urban environments with limited space. Yeah, you're already dealing with a limited palette of trees that can survive.

Jad: 4:23

Exactly.

Lilly: 4:24

And then you add these stricter guidelines.

Jad: 4:26

Yeah.

Lilly: 4:27

It does make things more challenging.

Jad: 4:28

Okay, so let's talk about, like why this rule is good.

Lilly: 4:31

Okay.

Jad: 4:32

Like. What are some of the benefits?

Lilly: 4:34

Yeah, so beyond just preventing this catastrophic tree loss.

Jad: 4:38

Right, because that's kind of obvious.

Lilly: 4:39

Which is a major benefit in itself.

Jad: 4:41

Yeah.

Lilly: 4:41

But there's more to it than that.

Jad: 4:43

So benefit in itself, yeah, but there's more to it than that.

Lilly: 4:44

So what else is there? So one of the most significant benefits is the enhancement of what we call ecosystem services.

Jad: 4:50

Okay, so we hear that phrase a lot.

Lilly: 4:53

We do.

Jad: 4:53

Yeah, ecosystem services.

Lilly: 4:55

A bit of a buzzword.

Jad: 4:57

But what does it really mean? How does tree diversity actually improve those services?

Lilly: 5:03

Right, so let's break it down a bit. Okay, when you have a diverse canopy, Okay. You also have a wider range of root systems.

Jad: 5:10

Oh, I see.

Lilly: 5:11

Right Different depths.

Jad: 5:12

Exactly, and that diversity in root systems. It actually helps to improve stormwater absorption and reduce runoff.

Lilly: 5:22

Oh, interesting.

Jad: 5:23

Much more effectively than if you had a monoculture of trees.

Lilly: 5:26

So it's not just about having trees, it's about having the right mix.

Jad: 5:29

It's about having the right combination of trees.

Lilly: 5:31

Yeah, to maximize what they're doing for you yeah. Exactly To create a more functional and resilient ecosystem.

Jad: 5:37

And that makes me think about this other article I read about oaks Exactly To create a more functional and resilient ecosystem. And that makes me think about this other article I read, okay, about oaks Okay. Like we tend to plant a lot of oaks.

Lilly: 5:45

Yeah, they're a popular choice.

Jad: 5:47

Because they support.

Lilly: 5:48

Right. They're known for A ton of biodiversity. Supporting a wide range of insects and wildlife.

Jad: 5:53

Right, but then we get these pests Right, but then we get these pests like the oak processionary moth.

Lilly: 5:58

Oh yeah.

Jad: 5:58

And the oak bark beetle.

Lilly: 6:00

Those could be a real problem, and they can just decimate these trees Exactly, and it highlights the point that even with a native species, that's generally considered beneficial.

Jad: 6:10

Right Like oaks are great, yeah, but.

Lilly: 6:12

Too many of them.

Jad: 6:13

Overplanting can create vulnerabilities Interesting. It can actually make the entire urban forest more susceptible to pests and diseases.

Lilly: 6:22

So it's all about balance.

Jad: 6:23

It is. Yeah, it's about finding that sweet spot where you have enough diversity to create resilience. Okay, so we were talking about the 5-10-20 rule Right right and how that's even more strict. Yes so it seems like some experts are saying like we need even more diversity.

Lilly: 6:39

Especially in areas with favorable growing conditions Okay when you have more options to choose from.

Jad: 6:44

But then there's that other side of the argument, Like we shouldn't just plant a bunch of random trees just to be diverse.

Lilly: 6:50

You don't want to sacrifice proven, well-adapted species just for the sake of ticking boxes.

Jad: 6:56

Like we could end up with the trees that just die.

Lilly: 6:58

Yeah, you could end up with trees that are not suited to the local environment. Yeah, and that defeats the purpose it really does. It's a delicate balance.

Jad: 7:07

And that reminds me of this one anecdote I read about the tree of heaven.

Lilly: 7:12

The tree of heaven.

Jad: 7:13

Yeah, have you heard of this one?

Lilly: 7:14

I have. Yeah, it's an interesting case, yeah.

Jad: 7:16

Have you heard of this one? I have. Yeah, it's an interesting case. It's this invasive species.

Lilly: 7:18

It is highly invasive.

Jad: 7:20

That's growing in.

Lilly: 7:21

It's notorious for its ability to grow in the most unlikely places.

Jad: 7:25

Yeah, like out of walls.

Lilly: 7:27

Yeah, I've seen pictures of it.

Jad: 7:28

And it's in Italy. Oh wow, in this town. Yeah, they thought they were.

Lilly: 7:33

They probably thought they were doing the right thing.

Jad: 7:34

Planting nice trees.

Lilly: 7:35

By planting trees.

Jad: 7:36

And it's become this huge problem.

Lilly: 7:39

And it just goes to show.

Jad: 7:40

Yeah.

Lilly: 7:41

That even well-intentioned planting.

Jad: 7:43

Yeah.

Lilly: 7:44

Can have unintended consequences.

Jad: 7:46

If you don't consider all the factors Exactly, it makes you realize how complex this all is.

Lilly: 7:51

It really does. It's a complex web of interactions.

Jad: 7:53

Yeah, and it gets even more complex. Yeah, yeah, and it gets even more complex when you think about extreme climates, right. Like think about those Nordic cities where they've got their native tree options.

Lilly: 8:04

Winters are already limited because of the climate.

Jad: 8:06

So do they focus on diversity or do they focus on hardiness?

Lilly: 8:10

That's the dilemma, isn't it? Yeah, because you want both.

Jad: 8:14

Yeah, you need trees that can survive.

Lilly: 8:17

Right, you need trees that can withstand the harsh conditions.

Jad: 8:20

But you also want that diversity.

Lilly: 8:22

But you also want to avoid the risks of a monoculture.

Jad: 8:25

So it seems like the 10-20-30 rule. It's a good guideline.

Lilly: 8:29

It's a good starting point.

Jad: 8:30

But it's not a perfect solution for every situation Exactly. It's more like a compass.

Lilly: 8:34

I like that analogy. Yeah, exactly.

Jad: 8:35

It's more like a compass.

Lilly: 8:36

I like that analogy. Yeah, it's like a compass, guiding us towards a more resilient urban future. Exactly, but ultimately, creating a healthy and diverse urban forest requires careful planning.

Jad: 8:46

Yeah. Taking into account both the big picture and the local context. So how are cities actually putting this rule into practice?

Lilly: 8:55

That's a great question.

Jad: 8:56

Like are they actually following it?

Lilly: 8:57

And it leads us perfectly into the next part of our deep dive.

Jad: 9:00

Well, perfect.

Lilly: 9:00

Where we'll explore how different cities are approaching this challenge.

Jad: 9:04

Okay.

Lilly: 9:05

Using various tools and strategies, so it's been fascinating to see how different cities are tackling this. Okay, one of the articles we looked at highlighted a tool called Tree Plotter Inventory.

Jad: 9:17

Tree Plotter Inter inventory yeah, it helps cities track data.

Lilly: 9:21

Oh cool On their trees, oh, and then see if they're actually meeting the 10, 20, 30 rule.

Jad: 9:27

So it's like a.

Lilly: 9:28

It's like giving a city's trees a health checkup.

Jad: 9:30

Oh, that's a cool way to think about it yeah. So can you give me an example?

Lilly: 9:34

Yeah, absolutely.

Jad: 9:35

Like how is that data being used?

Lilly: 9:36

So the same article mentioned a project called Diversitree.

Jad: 9:40

Diversitree.

Lilly: 9:41

Yeah, and they analyzed tree diversity.

Jad: 9:44

Okay.

Lilly: 9:44

In eight cities around the world.

Jad: 9:46

Wow Okay.

Lilly: 9:47

None of them were perfect.

Jad: 9:49

Oh really.

Lilly: 9:49

When it came to the 10-20-30 rule.

Jad: 9:51

Okay.

Lilly: 9:52

But some were definitely closer than others.

Jad: 9:54

So it sounds like cities are taking this to different degrees.

Lilly: 9:58

Yeah, some are definitely more proactive than others.

Jad: 10:01

Right, and we also have to remember urban forestry isn't just about planting trees.

Lilly: 10:07

That's a really important point. It's about managing the trees that are already there Right and planning for the future.

Jad: 10:12

Even with a native species, that's usually beneficial.

Lilly: 10:17

Right.

Jad: 10:18

Overplanting can be a problem.

Lilly: 10:19

It can create vulnerabilities.

Jad: 10:21

Yeah, it's like we said diversity is key.

Lilly: 10:24

It's all about balance.

Jad: 10:25

And I remember you were talking about the 5-10-20 rule.

Lilly: 10:28

Right.

Jad: 10:29

Which is even more strict.

Lilly: 10:32

Yeah, it takes the concept of diversity to another level.

Jad: 10:34

So some experts are saying yeah, some experts believe. We need to be even more careful.

Lilly: 10:38

Yeah, especially in areas that have really good growing conditions where you have a lot of options to choose from Then there's that other side.

Jad: 10:47

Right Like we shouldn't just plant trees to check the box.

Lilly: 10:50

You don't want to sacrifice trees that are known to thrive in that environment.

Jad: 10:55

And that makes me think about this quote I read OK, it said ill adapted species can be a problem at only a few percent OK Of a large street tree population.

Lilly: 11:06

I see. So it's not just about the numbers, it's about choosing the right trees.

Jad: 11:10

It's about making sure those trees can actually survive.

Lilly: 11:14

For the specific location.

Jad: 11:15

Which brings us back to thinking about local conditions. Absolutely Like we have to consider the soil.

Lilly: 11:21

Soil type is crucial. The climate. Of course.

Jad: 11:24

And even things like road salt.

Lilly: 11:26

Right, because some trees are more sensitive to salt than others.

Jad: 11:31

For a city.

Lilly: 11:32

Exactly.

Jad: 11:32

It's kind of like you know, creating an urban forest.

Lilly: 11:36

It's like composing a symphony.

Jad: 11:38

Oh.

Lilly: 11:39

Where each species plays a role.

Jad: 11:41

Okay.

Lilly: 11:41

Attributing to a harmonious and robust whole.

Jad: 11:44

And you need the right instruments.

Lilly: 11:46

Exactly, you need the right trees.

Jad: 11:48

For the music to sound good.

Lilly: 11:49

For the urban forest to thrive. Okay yeah, the right trees For the music to sound good, for the urban forest to thrive.

Jad: 11:52

Okay, yeah, I like that.

Lilly: 11:53

Yeah.

Jad: 11:54

And it makes me think about the long-term nature of all this.

Lilly: 11:57

It's a long-term investment.

Jad: 11:58

Like urban forestry, is a long-term investment. Absolutely, and it's about the future.

Lilly: 12:02

The trees we plant today will shape our cities for generations to come.

Jad: 12:07

Okay, so, as we wrap up today, yeah, we.

Lilly: 12:09

Okay, so as we wrap up today.

Jad: 12:09

We want to leave you with something to think about.

Lilly: 12:12

A final thought.

Jad: 12:13

Yeah, a question for you. Look around your neighborhood at the trees. Take a closer look. Do you notice any patterns?

Lilly: 12:19

Are there certain types of trees that you see everywhere?

Jad: 12:22

Are there too many of one kind of tree?

Lilly: 12:24

Yeah, exactly.

Jad: 12:25

So what would a more diverse urban forest look like?

Lilly: 12:29

It's a question worth pondering.

Jad: 12:31

Where you live.

Lilly: 12:32

Yeah.

Jad: 12:33

So we encourage you to go out.

Lilly: 12:34

Explore these ideas.

Jad: 12:36

All right. Thanks for joining us for this deep dive.

Lilly: 12:38

We hope you enjoyed it.

Jad: 12:39

We hope you learned something new.

Lilly: 12:41

And that you're feeling inspired to make a difference.

Jad: 12:43

And until next time, keep learning.

Lilly: 12:45

Keep exploring.

Jad: 12:46

And keep advocating for a greener and healthier future.

Lilly: 12:51

See you next time.

Roger: 12:54

Thank you for joining us for this episode of Talking Trees. We've delved into the importance of Santa Mora's 10-20-30 rule and its role in fostering biodiversity and resilience within urban forests. By understanding and applying these principles, we can better protect our city trees from the threats of pests, diseases and the challenges posed by a changing climate. Stay safe, keep planting and we'll catch you next time on Talking Trees. You.