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Most of us are familiar with the idea that having a diversity of species can lend resiliency to an ecosystem, but how often do we stop to consider the pros and cons of having a diversity of tree species in urban settings? What does an “urban” forest even mean in largely rural Vermont? In this episode, we talk with city arborists and watershed conservationists about these questions and what they mean in terms of resilience to invasive forest pests in the forest where we live.

Theme music was written and performed by Joanne Garton.

Music and sounds featured in this episode: 

• Coming soon!

Featured Guests (in order of appearance): 

• Vincent Comai, City Arborist, Burlington
• Warren Spinner, City Arborist, Burlington (Retired)
• Alison Adams, Watershed Forestry Coordinator, Lake Champlain Sea Grant, UVM Extension
• Shawn White, Project Manager, Friends of The Winooski
• Ginger Nickerson, Forest Pest Education Coordinator, UVM Extension
• Elise Schadler, Program Manager, Vermont Urban and Community Forestry Program, VT Department of Forests, Parks and Recreation

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Resources

For more information about emerald ash borer, visit: Vtinvasives.org and listen to Heartwood Episode 6: Losing Our Ash.

Urban Environments are Hotspots for Invasive Pests An article summarizing a 2022 study about the relationship between the lack of diversity in urban tree species and invasive insects.

Options for protecting ash trees with insecticide treatments. Factsheet produced by Vermont Urban and Community Forestry Program.

Vermont Urban and Community Forestry Program Tree Selection Tool. Use this tool to help select the right tree for the right place.

National Audubon Society Native Plants Database Enter your 5-digit zip code to use Audubon’s native plants database and explore the best plants for birds in your area.

UVM Lake Champlain Sea Grant Watershed Forestry Partnership facilitates research, communication, collaboration, and implementation of forest restoration and management practices that protect water resources in the Lake Champlain basin. 

Xerces Society for Invertebrate Conservation is an international nonprofit organization that protects the natural world through the conservation of invertebrates and their habitats. Their website has loads of resources on helping pollinators and other beneficial insects.

Get Involved

Join the Friends of the Winooski River in their mission to safeguard and enhance the natural resources of the Winooski River watershed. They have lots of opportunities to get involved.

Homegrown National Park Learn how you can answer Doug Tallamy’s call to regenerate biodiversity in the U.S. by planting native species, one yard at a time.

Vermont Alliance for Half-Earth Join with other residents who have come together to advance biodiversity in Vermont by the half-yard, half-school, half-town, half-valley, half-watershed and half-state.

Garden for Wildlife by National Wildlife Federation has an abundance of tools and resources to create outdoor spaces that support wildlife of all kinds.

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Episode Transcript

V.J. Comai: We've learned our lessons in the past, I mean, prior to my coming to this planet, the northern forests were dominated by the American chestnut and then the chestnut blight came in and wiped them all out. And then we had the American Elm and Dutch Elm disease, which came to the country in the early 1930s and wiped out all the elms, and is still killing elms. And so and now we have emerald ash borer and there's others coming down the pike.

Kate Forrer: Welcome to Heartwood Vermont, a podcast that connects Vermonters to our forested landscape through stories. And answers your questions about our forests, their management, and the forest economy.

Lisa Sausville: We’re your hosts Lisa Sausville, from Vermont Coverts Woodlands for Wildlife,

Kate Forrer: and Kate Forrer, with the UVM Extension.

Lisa Sausville: In past episodes we’ve talked about the importance of diversity to improve forests for wildlife and resiliency in the face of invasive species and climate change.  In this episode, we are going to continue that conversation but with a different lens. We’ll be exploring urban forests and why species diversity is important when we think about trees in the public, developed, spaces where we live.

Lisa Sausville: OK Kate, what do we really mean when we are talking about urban forestry?

Kate Forrer: In Vermont, it’s the trees in our downtowns, it’s the trees along our sidewalks, it’s the trees on our town greens, or even the trees in our public right-of-way, out on our dirt roads.

Lisa Sausville: So these conditions that these trees undergo, that they live in, they are different than in our forests. When we talk about the forest on the top of Mount Mansfield for example, or anywhere in the Green Mountains.

Kate Forrer: You are absolutely right, Lisa, it is the conditions that are really the important part here. And that as those conditions change, our considerations for management need to change. Steve Sinclair, who is our past state forester, had a really great way of articulating the value of these trees and also how to think about our urban forest here in Vermont. And the way that he described it is that our forests here in Vermont exist on a continuum. So it’s not that our urban forests is one area and our rural forests is another, but it is really a continuum from downtown Burlington on Church Street all the way up to the top of Mount Mansfield. It’s really all one forest - it’s the forest in which we live, work, and play.

Lisa Sausville: Also thinking about connectivity for wildlife - I like it!

Kate Forrer: Absolutely, and trees play an essential part in our local landscape. As we’ll hear from some of our guests, some of the many, many benefits that trees provide.

V.J. Comai: ….For starters, they're a long term carbon sink. They're sequestering carbon. They're cooling areas. 

Warren Spinner: Stormwater management.

Alison Adams: Planting trees can really help trap phosphorus, because that phosphorus runs off in sediment and then the trees can help trap the sediment on the land before it gets into the water. So having those intact forests right up against waterways is a really important way to protect water quality in the lake and its tributary streams and rivers.

Shawn White: You also create habitat for birds, for caterpillars, for insects, for, for all kinds of animals.

Lisa Sausville: That was V. J. Comai, who you also heard from at the beginning of the episode, Warren Spinner, Alison Adams and Shawn White. We’ll hear more from them throughout the episode.

Lisa Sausville: So Kate, you work for the Urban and Community Forestry Program out of Extension, can you tell us a little bit more about that program?

Kate Forrer:  Absolutely, Lisa. Our Program is actually a partnership between UVM Extension and Vermont Department of Forest Parks and Recreation.  We provide technical, education, and financial assistance to communities to help them in the care and management of their public trees and public forests. And when I say public forests, I mean things like town forests. We have many communities in the state who actually own forest land. We do everything from inventory work, to help communities get a sense of what their urban forest and public resource looks like, to managing those rural roadsides that we talked about earlier, and thinking about some of these invasive forest pests.

Lisa Sausville: Oh that’s cool. So there’s a bunch of you that manage this program. It looks like you brought someone along today to chat with us?

Kate Forrer: I did, I brought my colleague Ginger Nickerson back. Ginger is the Forest Pest Educator with the Urban and Community Forestry  Program. Welcome, Ginger.

Ginger Nickerson: Hi, Kate! I’m excited to be back here with you and Lisa today.

Lisa Sausville: So Ginger, you pitched this episode to Kate and I, to talk about urban and community forestry. Why is it important that we have a conversation about this topic?

Ginger Nickerson: So, I help municipalities and community groups prepare for invasive pests and diseases that might affect their public trees and forests.  I wanted to share a story unfolding across Vermont today. As many people know, many years ago, many towns across Vermont and across the nation lost their elm trees in their downtowns and urban areas to Dutuch elm disease. And these towns then replanted with ash trees in their public spaces, but now municipalities around Vermont are faced with losing their ash trees to emerald ash borer.  So as we move forward it’s really important that we start thinking about having a diversity of tree species in our public spaces. 

Lisa Sausville: So when I think about forestry diversity, I think of different types of trees, so different species, but I also think of woody debris on the ground, standing dead trees, different age classes, and sizes.  So having a lot of these types of diversity support a healthy forest and provide habitat for wildlife in general. But it sounds like we are not going to have a lot of that in our public parks because people want to have a picnic or whatever. So what does that actually mean for diversity in those areas?

Kate Forrer: So Lisa, it’s true, we are thinking about different things, but we are also thinking about things you mentioned - we are thinking about age class, we are thinking about species diversity,  and we are thinking about structural diversity.. But for the purposes of this episode, when we are talking about diversity, we are really specifically talking about species diversity.

Lisa Sausville: Alright, so when I think about what Ginger has said, and what you have said, and I think back to pictures I’ve seen of these Elm streets. They’re named Elm street because they had all these elms growing down them and they liked  it because it was uniform and it gave streets that uniform look.

Ginger Nickerson: But unfortunately, that uniform look came at a cost. One of the people who I spoke with was Warren Spinner, the retired City Arborist for Burlington. I’ll let Warren share what happens when one species is over-planted.

Warren Spinner:  American Elms are beautiful. Their structure is perfect for the urban environment. They grew like a vase, so they were up and out of the way, you could put your infrastructure underneath them. And that's one of the reasons they got over-planted.

Warren Spinner: Many cities in the US on the East Coast and Midwest were lined with American elms, and they were typically planted back starting around probably nineteen hundred nineteen ten, and they planted them right up through the even into the 40s and 50s. And then a disease was introduced from Europe, called Dutch Elm Disease, which most folks are familiar with. And that was the start of the decline of all the elms throughout the region, northeast and especially Burlington. It was told to me when I started that Burlington had 10,000 elms at one point [in the public right-of-way].

Warren Spinner: When I got there - streets that had no trees. I can think of a number of streets that I would drive down and there'd be nothing but elm stumps because they hadn't quite caught up with the stump removal.

Kate Forrer: Life is really hard for urban trees and unfortunately, there are only a few options of trees that can do well in urban settings. So for cities and towns that lost their public elms, they really only had a limited choice of trees to replant. Our Urban and Community Forestry program manager, Elise Schadler, with the Department of Forests and Parks, explains it really well.

Elise Schadler: The urban environment is so tough on trees that you also have to really think about one, diversity, but also just what's going to survive. And a lot of those soils were just like backfill and rubble and not like ideal growing conditions. So there were a limited number of trees, and - it's a big challenge in urban forestry, is just finding trees that are tough enough to be able to deal with that environment. And maybe you're over-representing those trees because you try other things and they just don't work time after time, you just fall back on those really tough urban trees.

Ginger Nickerson: This was certainly the case for Burlington.  So here is Warren again, talking about replanting the city after the loss of their elm trees, and how getting a diverse number of species that could thrive in the city was a challenge.

Warren Spinner: So a new mayor was elected by the voters at the time, who was Bernie Sanders. So when he was driving around the city, he definitely noticed the streets vacant of trees and wanted to do something about it. So the initial start of the reforesting of Burlington happened around the early 80s, and the very first major tree planting we did in 1983 was, in the spring, we planted 600 trees with volunteers [in one day].

Warren Spinner: And my role was getting the trees. So you can imagine a young arborist with a feat of trying to locate, find, and get 600 trees that were of the size that volunteers could easily move them around. That was one of my issues then, is that the diversity of the trees, I didn't have a whole lot of choice, because of the numbers we were getting.

Ginger Nickerson: So they ended up planting a lot of ash.

Warren Spinner: Green ash and white ash got over planted because they worked in the urban environment. And you could put them in the ground, you could mis- plant them, you could plant them too deep and they'd still live. You could do all kinds of bad things to them and they would survive, you know? So developers, architects, everybody, arborists… We were all using that tree. 

Kate Forrer: Listeners, you may remember from our last episode that ash trees are threatened  by emerald ash borer, or EAB. If you need a quick refresher on this issue, check out our last episode.

Lisa Sausville: It seems like planting just a few species of public trees is like that old saying “Don’t put all your eggs in one basket.” If you plant a monoculture, or just one species, and a pest or disease comes along, you have a chance of losing them all.

Ginger Nickerson: Exactly, Lisa. V.J. Comai is the current City Arborist for Burlington.  He and Warren talked about how emerald ash borer drove home the lesson that the best way to prevent losing all of your street trees to one tree-specific pest is to plant a diversity of trees.

V.J. Comai: When I came on as city arborist, within weeks, the first detection of emerald ash borer in the state. So it was a lot all at once.  I was very aware of the imminent threat of emerald ash borer. I knew it was coming. I hoped I'd have more time. So I was just getting my feet under me here in the city and getting familiar with our inventory software system, our systems in general, learning my crew, and what they did on a daily basis. So it was a lot. So, immediately I took full advantage of our inventory software system, called Tree Works, to identify the location of every ash within our care throughout the city. And that was a great tool because I could really key in on the areas with ash.  And then I got in the truck and rode around and visited all of them, and started to think about what would be our approach moving forward, knowing that it was only a matter of time. Just about 10 percent of our inventory trees at the time I came on were ash, either green or white ash. So instead of a challenge, I looked at it as an opportunity to start diversifying our canopy more.

The list of tree species that can tolerate urban conditions and don't get very large, can be planted under overhead utilities, is fairly limited, and we’ll see what works. But with a warming climate, who knows? Down the road, we may be planting some species that you normally wouldn't think of planting this far north and trying them on a limited basis. Since I've been here, we've been planting some tulip trees, sweet gum, shingle oak, which there was none of in the city prior to my coming here. We just started in the last couple of years planting Cornelian Cherry dogwood. You know, we're doing flowering crab apples and Japanese tree lilacs, some Hawthornes.

Lisa Sausville: So some of the trees V.J. mentions are not native. Normally, we are encouraging landowners and others to target and select native species.  Why would towns or cities be choosing something other than natives?

Kate Forrer: I’m glad you brought this point up, Lisa. It’s really complicated. Normally I would agree with you, that natives are the best option. But when we are talking about urban conditions, finding a native species that can thrive in these conditions is really hard. And so, it’s really about a species that will fit the site and the growing conditions.  Sometimes native species work, and sometimes they don’t. If we think about urban forests as part of that forest continuum that I was talking about earlier, there’s definitely a lot of advantages to planting native species. If they can work in the space.  You have to think about things like salt spray, compacted soils, or the various characteristics of a tree that we as humans are willing to put up with. I use the example a lot of oak trees - there’s a reason we don’t plant oaks in our sidewalks and along our roads.

Lisa Sausville: People don’t really want acorns raining down on their cars….I never really thought about that.

Kate Forrer: Or on them, hitting them on the head. The sky is falling, the sky is falling! I must go tell the…

Lisa Sausville: Chicken Little, Chicken Little!

Kate Forrer: So the best ecological choice is a native, obviously, but that is not always the choice that works best for people and the trees that we like to plant.

Lisa Sausville: Yeah, I guess I would always argue for planting native species because there’s a lot of advantages to planting them. The insects and birds in an area use native trees as pollen and food sources because they co-evolved together. But if you plant a non-native tree, or even a cultivar, it may not provide those benefits. So I understand the tug-of-war that is going on, but I’m still plugging for natives.

Ginger Nickerson: You’re not alone, Lisa. Two of the people I spoke with,  Alison Adams, the Coordinator for the Vermont Watershed Forestry Partnership, and Shawn White, Project Manager for Friends of the Winooski, are both thinking about that kind of biodiversity and the ecological resilience it provides for their work planting trees in riparian areas. 

Alison Adams: Those are the species that are adapted to this landscape. They are less likely to present invasive species’ problems. We want to be encouraging the ecosystems that are specific to this area, the ones that are going to support the wildlife that's native to this area. The ones that are going to be culturally significant to this area. Those are the species that we really want to be planting in restoration projects. Locally sourced trees are additionally important, not necessarily more important, but additionally important because trees that are grown locally can help support the local economy and the local workforce. Trees that are grown locally  are likely more genetically adapted to the local conditions.

Shawn White: And the trouble with ornamentals, you know, they look beautiful. They often don't have very many pests. You know, they don't get eaten. the leaves, don't get holes in them and that sort of thing. But if you're really looking at restoring your yard for the purpose of biodiversity, you want plants that get eaten. You want to support the native insects, because those insects then feed birds and other organisms, frogs and toads. And if you view your yard a little bit differently and think about it as being really part of an ecosystem, as opposed to being something that you just sort of look at as you know, just something aesthetic. Then you start to want to have your plants feed that ecosystem.

If you are just worried about water quality and runoff then yes. An ornamental plant, an ornamental tree, is still going to serve that purpose. It's going to absorb water, it's going to intercept rainfall. The reason that native plants work much better at supporting an ecosystem has to do with the food chain. The next step up on the food chain often from the plant itself is insects and most insects are specialists. They will only eat a couple of species. 

We hear a lot about how Monarch populations are crashing, it's not just the Monarch. There are other insects too that are really suffering. We're in a situation where a lot of their populations are crashing. If the insect populations go down, then we can expect that the bird populations will be further decimated. They are already much less than they used to be. Almost all bird species feed their babies caterpillars or insects. And so if we want to grow birds, we have to grow insects.

Ginger Nickerson: Friends of the Winooski has a project called “Lawns to Forests” that helps people plant trees in their yards to protect waterways.

Shawn White: The fact that people had so much lawn would contribute so much to excess runoff pollutants, you know, because they would carry fertilizers and pesticides. And so anything that's running off of these big lawns that often people have, those are having a big impact on rivers and streams.

We really felt like one way that we could be very effective in keeping rivers and streams clean and healthy, and to restore that ecosystem, is to help community members restore their own yards. Reduce the lawn that they have, plant hopefully woody, native vegetation, so trees and shrubs, that could repair all of those things that are wrong with just lawn. And to restore the ecosystem too. because in addition to all those water quality benefits and stormwater volume reduction, you also create habitat for birds, for caterpillars, for insects, for all kinds of animals. So, you're really restoring the natural biodiversity that was eliminated when this monoculture of lawn was created.

Lisa Sausville: That’s great. I’m really glad to hear that watershed restoration groups are thinking about supporting insect populations by planting native trees. Restoring riparian areas is also important for providing corridors for wildlife to travel along.  Wildlife likes it messy -  they don’t want it all cleaned up. You can save money by mowing less, or not mowing at all, or selecting areas that you don’t mow - and you are going to do good things for wildlife. Through VT Coverts, we work to educate landowners and others about the importance of habitat connectivity and working to improve habitat for wildlife and this can be done on a very small plot of land in town to someone who has a hundred acres or more.

Kate Forrer: This all  brings us back to the idea that it is really one continuum of forest - and that trees planted in our developed areas are actually connected to this larger landscape and provide that connectivity that you are talking about for wildlife -  which includes insects. 

Ginger Nickerson: Right, and the folks that I interviewed talked a lot about that tension between people wanting to plant native trees to benefit wildlife and the fact that not every native species is going to be able to thrive under the stresses in developed areas.

Warren Spinner: How come you can't use native species? You know, how come you're used in European species and not native species? It's about handling the adverse conditions that you're planting the tree in.

Elise Schadler: I think some people feel really strongly about native trees, and that's really great. I would also stress that something that truly, truly, is something that needs to be considered is just that an urban tree has a harder life than not urban. So when we think about it like, “OK, here are all the species that might do well in this site because of the underground growing conditions like the soil type and the drainage. And here's all of the species that that list will be narrowed down by. Is there any overhead infrastructure? Are there sidewalks that they're going to have to worry about? Is there salt load that's going to go on that site that might impact the root systems?” So you start with a big list of trees and then you start narrowing it down. And the order in which you narrow down that list might change. Perhaps your first narrowing factor is native versus non-native. So then you go through the rest of those decisions with a smaller list and you get to whatever ends up being the right tree for that space. We support all of it as long as they're planting the right tree in the right place in the right way.

Ginger Nickerson: So it’s really complicated. On top of this tension between native and non-native species, there’s climate change to worry about. Many of the factors that we’ve talked about are changing, and the stressors that urban trees are facing are less predictable, such as invasive pests, droughts, and storms. All of the people who I spoke to mentioned that making sure that we have a diversity of trees in our backyards, and town parks and other developed areas is  important in terms of giving us more resilience in the face of climate change.

V.J. Comai: You know, we think about climate change. Quite honestly, what's what's going to hold up? We're always looking for new species to try on a limited basis and see how they fare. It's a tough world out there for an urban tree.

Burlington is built on a hill essentially. It’s got a very antiquated combined stormwater sewer system in many parts of the city. So we get these epic downpours. We tend to have more intense storms, I think, with climate change where we get heavy, heavy rains. The more canopy you have, the slower the impacts of those downpours, you know, the tree is catching a lot of water. And some of it is never hitting the ground. It's staying on the leaves and evaporating or being absorbed by the roots of the trees. That's really significant.

Elise Schadler: I think a lot of urban planners and urban foresters really took the lessons from elm and now ash into consideration as they're thinking about the future urban forest. And there's that [climate] change piece that I spoke about. But there also is just the realization that when you've got a large population of one or two species, we don't know what's coming down the pike as far as pests, and there's going to be something. And so if you have these monocultures or just non-diverse street tree populations, if you've got a ton of maple, which a lot of towns in Vermont do, when we get something that really threatens those trees, then you are facing a big loss there. 

We are in a period of unprecedented change, and we also don't really understand how that change is going to roll out. So I think the wisdom is just realizing that the more diverse a population of trees you have, the more likely you're going to have some resilience to that change.

Lisa Sausville: So we’ve talked about why it is important to plant trees in these areas, but who is actually doing this work?

Ginger Nickerson: Elise Schadler talked a lot about that….

Elise Schadler: By and large, a lot of the tree planting and stewardship efforts that are happening in municipalities are happening from volunteers. So this might just be an ad hoc group that focuses on tree stewardship and other environmental issues in a town. Or they might be the Conservation Commission members, or they might be a tree board, or they may be a town forest committee, something like that.

Kate Forrer: There are also Vermont Tree Wardens as well. These are folks who are actually appointed in each community to be responsible for the stewardship and care of our public trees.

Ginger Nickerson: So because trees are so good at slowing down water and filtering run-off, we are seeing a lot of watershed organizations in Vermont do a lot of tree plantings on both public and private lands.  Alison Adams and Shawn White represent just two of the watershed organizations that are planting trees in riparian areas in Vermont. At the Urban and Community Forestry Program, we are seeing more interest from municipalities in planting trees to protect their waterways. And this brings us back to this image of the forest that we live in as a continuum. It is really just one canopy.  And there are lots of different groups with different interests planting trees in our cities, towns, and villages.

Lisa Sausville: OK, so I am hearing  that having a diversity of species is important, not just in what we typically think of as forests, but in other areas where trees are planted - like on our city streets  And, if we plant a diversity of species we should have some protection or resilience - so that when the next insect or disease comes along it won't wipe out all the trees like it did with Dutch elm disease and emerald ash borer. 

Kate Forrer: That’s right, Lisa, and where we can, we should be considering planting native trees because of all those benefits that we’ve talked about. So here are a few things that our listeners can do.

Elise Schadler: Start by getting to know the trees a little bit. You know, if you don't have a tree ID book, get one. There's some really great ones out there. Learn to identify the trees in your yard and your neighborhood. Start to have an idea of what is planted in the right-of-way or planted on public land, if anything.

Shawn White: You can go pick up acorns off the ground and plant them. I mean, that's an easy way to do things and it's not hard at all. Find a native tree that you like, find some seeds on the ground when they shed their seeds, plant them in your yard.

V.J. Comai: I think if you have the opportunity to plant trees on your property, plant trees. We're planting for the next generation and it's important. 

Lisa Sausville: Oh boy, these are some great ideas. And remember, another idea was to mow less often, or carve out areas where you are not going to mow, and leave it messy for wildlife. Kate, what are some of your go to resources?

Kate Forrer: Oh my gosh, there are so many great resources out there. There are just way too many to share with listeners right now.  Especially since we know that most of you are listening to this in your car, or while you’re cooking dinner.   We’ve actually  generated a list in the show notes for listeners to check out when they have a minute.

Lisa Sausville: So we talked about what people can do on their own properties, but I want to bring the focus back to urban trees- the whole idea for this episode, Ginger, let’s bring it back to the  trees.  Tell us what people can do to help  the urban trees in their community?

Ginger Nickerson: So as we heard from both Elise and Kate, most of these efforts are volunteer-driven, and most communities would welcome folks getting involved in taking care of their public trees. Listeners can join a tree board if their town has one, join a conservation commission, or volunteer with a local watershed group. There are lots of ways that people can get involved in promoting diversity in your community’s trees. We’ll have links to some of these organizations in the show notes.

Kate Forrer: Thank you to all our guests, VJ Comai, Warren Spinner, Elise Schadler, Alison Adams, and Shawn White. And a really huge thank you to our special guest, Ginger Nickerson from UVM Extension. 

Ginger Nickerson: Thanks for having me, Lisa and Kate.

Kate Forrer: Ginger, can we count on you coming back?

Ginger Nickerson: Absolutely.

Kate Forrer: This has been Kate Forrer

Lisa Sausville: Lisa Sausville

Ginger Nickerson: And Ginger Nickerson.

Kate Forrer: You’ve been listening to Heartwood Vermont, hosted by Vermont Coverts, UVM Extension, and UVM’s Center for Research on Vermont.

Lisa Sausville: This episode was produced by Leah Kelleher and made possible by funding from the Vermont Agency of Agriculture, Food and Markets, and the USDA APHIS. The interviews we heard were conducted in collaboration by the podcast team and Ginger Nickerson. Thanks for listening.

Do you have a question or story to share about your connection to Vermont's woods, or want to participate in a future episode? Please email us!