Episode 3 transcript: What trees give back

This is episode 3: What trees give back

Maya Lach-Aidelbaum: We all know food and oxygen are necessary for our survival, but have you ever thought of these things as services provided by ecosystems? Clean air, flood control and spiritual well-being are all examples of ecosystem services.

At Concordia, many researchers are doing work to better understand these services. Which is better: small patches of dense urban forests or trees distributed more evenly across the city? What ecosystem services do different tree species offer?

We still don't have all the answers, but a newly planted plot of trees on Concordia's Loyola Campus will help researchers better understand the benefits of different types of urban tree formations. This plot is also part of a wider network of research sites.

My name is Maya Lach-Aidelbaum, and I'm a master's student in media studies at Concordia University. I'm interested in our relationship to urban spaces and the environment.

Today, we'll hear from two different Concordia researchers to hear more about how this plot is helping advance knowledge on the ecosystem services of urban trees.

First, we'll hear from Bella Richmond. She's a PhD student in Concordia's Department of Biology, who studies the benefits that trees provide in cities.

Next, we'll hear from Emma Despland, a professor in Concordia's Department of Biology. Her research mainly focuses on plant-insect interactions, but she's also interested in how scientists contribute to shaping climate policy. And she actively supports grassroot conservation efforts and is a proponent of citizen science projects.

Bella Richmond: Ecosystem service very simply is just a benefit that humans receive from nature. Generally, we split ecosystem services into four categories.

There's regulating ecosystem services, which are the things we hear about most often. That is something like cooling or temperature mitigation, flood mitigation, the reduction of air pollution — those are all regulating ecosystem services. They're controlling our environment and reducing harmful effects of our environment or providing benefits.

There's supporting ecosystem services. These ones are more theoretical, harder to grasp things that allow the ecosystem to provide other benefits. Soil formation or nutrient cycling are both examples of supporting ecosystem services.

There are provisioning ecosystem services. These are the things that when we get a tangible material gain. Pollination results in all our food production — that's a provisioning ecosystem service.

And then finally, there's cultural ecosystem services. This is the increased sense of place you have because of a tree in your backyard. That's a cultural ecosystem service. The improvement in your mental health when you're exposed to green areas, that's a cultural ecosystem service.

My PhD, very broadly, is about the benefits that humans receive from green infrastructures, specifically in cities. What factors drive our ability to receive benefits from green infrastructure?

We consider green infrastructure to be any sort of green infrastructure that has a vegetated component. That includes things like green roofs — I feel like that's something people often think of when they think of green infrastructure. But it also includes things like parks, it includes when you see curb cutouts with flowers — we've seen more of those in Montreal — that's also green infrastructure. Living walls, that's green infrastructure. It's something that we build, but it has a vegetated component — it's green infrastructure.

Trees — because they provide such a disproportional amount of ecosystem services or benefits to people — they were a big focus of my research and of urban green infrastructure research in general because they are so important to a lot of the benefits that we receive.

One of the studies I did was looking at how the history of a park influences its ability to cool now. What did the park used to be? Did it used to be a landfill? Did it used to be a quarry? Did it used to be a forest? Did it used to be a farm? Does its history drive how much cooling it's providing to people now?

I found that the answer to that question is yes. We see that in places that were previously industrial — like quarries or landfills — we see that parks in those areas are cooling less at night. And this is perpetuating both historical and current environmental injustice. Previously industrial areas often inhabited by racialized or low-income folks or both — because they're not desirable places to live, and they are often subject to pollution and other environmental hazards.

Continuing that thread through time, the parks in those areas also provide less services today. That means that community is continually being subjected to environmental injustice. You can imagine if you have a park that's surrounded by single-family homes with yards, the surrounding area may not be as hot. And so, it's easier to cool.

Industrial areas very much located central and east in Montreal are surrounded by areas that are quite hot and so might be heating up more. But also, they have — in general — less trees. If we think about converting a previous forest into a park, you can imagine that there may already be trees there when you're changing the land use type into a park. You might plant some new trees, but you have some trees to work with.

Same with farm — there's usually some sort of trees on farmland to create wind barriers. When they're converted into a park, they have this starting place to work with. If we think of Lafontaine, for example, that's a park that used to be a farm. Those huge trees that we see are remnant farm trees.

Whereas, if you think about converting a quarry or a landfill into a park, you're basically starting with a brand-new slate. You literally have to bring in the soil — you're very much starting from scratch. These parks often just have less trees, and sometimes the trees are smaller depending on the conditions in which they're growing.

Something important about ecosystem services is that they are very reliant on what people need. Providing a service or benefit to someone who doesn't need that isn't a true benefit. If I'm cool — I don't feel hot — and a tree is cooling the air, it doesn't matter because I wasn't hot to begin with. It's no longer a benefit.

It's not necessarily that trees are doing different things in cities than they are in forests or rural areas, but the needs that we have for our quality of life in cities are really different. Flooding is not such a big deal if you're a tree living in a forest. It's not great, but you don't have home insurance and a basement to flood.

It really is the context in which these trees live that determines the services they're providing because the way we frame ecosystem services is the benefits to us. It's really what we need. It's just this really hard thing where we're asking a lot of our trees all the time. And then we're not even getting into — do we want it to be good habitat for birds? Do we want native insects to be able to forage and live on these trees?

We're asking so many things from a single tree. For example, for cooling, there's this tension. Really dense forest stands provide more daytime cooling. This makes sense. When you're in a forest and you're under complete shade — there's multiple layers of canopy, you look up, you just see leaves — it makes sense that you're going to be cooler just from a shade perspective.

But at night, areas with really dense trees and canopy are actually warmer because the hot air can't escape — the canopy traps it. Even with this one service, this one benefit, there's this tension. Then if we add any other benefit like pollination — flowering trees aren't large trees generally. If you think about apple trees or cherry trees that we see in the spring flowering that we love so much — lilacs, magnolias —, those are very small trees typically. They're not going to be great cooling trees necessarily,

It's hard being a city tree. You're trapped in a little concrete square. Often, it's really hot. There's a lot of salt — you get coated in salt every year. People lock their bikes to you. There's pests — there's invasive species. It's hard, and so a lot of the species that we plant in our cities are not native because they need to be from an environment or climate that's actually warmer than ours because our city is warmer than our native climate.

Or more resistant to drought because plants here aren't used to drought. But in the city, they experience drought. We have a relatively small subset of trees that works in the specific urban environment that we have.

I think that going back to that really basic question of what is this tree's purpose — what do we want this tree to do? Do we want it to cool? It can have multiple purposes, but the answer to that — where to plant it and what species it should be — is really tied to what we want it to do over the course of its life.

And do we have the resources to maintain it? Because tree maintenance and management is just as important as planting a tree in the first place. A lot of trees planted in cities die. But also, what are the community needs? What does the community in this place want and need from its green spaces and its trees? That's going to be really different depending on where you are in the city.

I think having people connect and love nature and the trees that surround them is a really important part of continuing to value nature in our society and continuing to have people that care and want to see more of it. Having a very participatory process and then choosing the tree species and the place that is best for that tree's life is also really important.

Maya Lach-Aidelbaum: That was Bella Richmond, a PhD student in Concordia's Department of Biology, who studies the ecosystem services of urban trees.

Now, we here from Emma Despland, a professor in Concordia's Department of Biology. She's an expert on plant-insect interactions and is invested in grassroots conservation efforts and citizen science projects.

Emma Despland: The main idea with the research at this plot was a partnership with Soverdi. They are the organization who came and planted the trees. They're overall an organization — this is what they do is plant trees in Montreal.

They grow trees in nurseries, and then organizations — whether it's businesses, schools, daycares, hospitals — who want to plant trees on their property, they contact Soverdi. Soverdi comes, they check the place out and they have the expertise to make decisions about what are the best trees to plant here, which are the ones most likely to survive — and they do the planting.

The main initiative of research here was to work with Soverdi to look at different planting regimes — like different ways of planting — to see which one would give best success. This research plot, part of it is planted with all trees of the same size. Another part has a mix of bigger, fast-growing species and smaller, slow-growing species.

The idea that that way the fast-growing species would have a bit of an edge because they'd already be bigger, they would grow fast, they would then produce shade, and then the slow-growing species would be able to grow up under that shade. It's mimicking that natural processes of succession.

What they did on the research plot here is to split it two halves: one half is fast-growing and slow-growing trees all the same size, the other half with these two different sizes to see if you got better success with the two different sizes. In some ways, it doesn't sound like really exciting research, but it's useful, and it's things they needed to know.

Because obviously planting small trees is cheaper and easier than planting bigger ones. But if the bigger ones give you better success rate, then maybe that's worth it.

There are a lot of students coming from nature-deficient backgrounds. People who — they come with a lot of really good book knowledge and a lot of passion and a lot of interest. But that tends to have been fed more from watching nature documentaries than from actually having spent a childhood hiking and camping and so on. They maybe didn't have access to that.

They're studying ecology, but they can't, for example, identify any local tree species. That's a huge gap in their knowledge. That plot will be able to help remedy that, I think both in terms of formal classes we teach, but also as more informal pedagogy. If the forest is there and the names of the trees are present, then it can be a self-taught experience for any student to just go there and look at them and acquire this knowledge themselves.

I think one of the ideas of the mini forest is you quite often include the community in planting it, so people have a feeling of attachment to — you know — "that's my tree, and we planted this together." It's often done with an organization of people who work together. It makes this community, team spirit of we planted this together. And then when it grows up as a forest, it becomes this small but beautiful space, which maybe fosters a different sense of attachment than a row of trees would.

I think having a multiplicity of approaches is not a bad thing. If you think of our campus, for example, along Sherbrooke there's a row of large trees — and that has value. As they get large, there's still space for them. I think along streets, having rows of trees makes a lot of sense. The mini forest — that's a squarish space that's not really used. A mini forest might be a good way to fill that space with a mini ecosystem. It's a different goal for a different sort of space.

I was at COP15 a couple of years ago where international commitments were made to protect biodiversity, and there were some strong commitments that needed to be made before 2030. But António Guterres, who's the head of the United Nations — the secretary-general of the United Nations — had said something, I'm paraphrasing here, but that redefining our relationship with nature needs to be the top priority for the 21^st century.

Seeing people come together to plant a forest is a first step towards that — towards that healing our relationship with nature. And that's exciting to see people coming together and doing this. Another aspect is thinking of the long term. Those trees will still be here in 50 years — that's a nice feeling.

The goals tend to be concrete about doing things, like protecting a certain amount of space or slowing numbers of extinctions of species or restoring damaged ecosystems. Or one of the main ones is mainstreaming biodiversity. Mainstreaming is a word I've thought a lot about because I didn't used to think this was a verb — but it is now —, and what it means is that any major decision that gets made has to take into consideration the impacts on biodiversity.

In a way that I find helpful in thinking about that is it's similar to safety. No matter what you're doing, you have to consider the safety of the people involved. The COP15 requires us to mainstream biodiversity in the same way. That's very hard to do if there's no measures. If you're an engineering firm — let's say — building a new headquarters, what does it mean you have to mainstream biodiversity, you have to consider biodiversity? How do you do that?

You can hire someone to greenwash and to say, "Oh look, we planted a tree." But if we want people to take meaningful steps, we have to define what those meaningful steps are. In the same way that if you're building a building, you can take energy efficiency seriously. To do that, there is a list — if you do these eight things, you will get gold certified. If you do these 10 things, you will get platinum certified. Those things that you need to do have been defined by experts as being the most effective things you can do in terms of limiting your carbon footprint or having lower energy use.

We don't have that list yet for biodiversity. But if we want corporations to take meaningful steps to protect biodiversity, we need to give them a list of what they need to do. Because otherwise, the temptation is to greenwash. That's where research on mini forests can help tell us — are we going to put planting trees on that checklist of things that urban developers need to do? Do we say just plant trees or tell them a specific way of planting trees to give them meaningful targets that they can reach.

Maya Lach-Aidelbaum: From ecosystem services to citizen science, today's discussion highlighted how trees in cities do more than just provide shade. They contribute to our health, climate resilience and community well-being.

Thanks for listening, and make sure to head to the last stop of our podcast walking tour.