How Tree Shade Data is Collected & Why it's Important

0:00SPEAKER_01:Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oester. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much, much more. Tune in every Thursday to learn more because here at the Talking Trees Podcast, we know trees are the answer. I'm joined this week by Jason Henning. He's the manager of ecosystem services for the Davy Institute in Lancaster, Pennsylvania, and Jay Hepler, project manager for the Davy Institute in Syracuse, New York.

0:37SPEAKER_01:We're talking all about urban forestry and how shade helps our cities and more. Jason, in your case, welcome back to the show. And Jay, welcome to the show. How is everybody doing?

0:47SPEAKER_02:Good to be back, Doug.

0:48SPEAKER_01:Great to be here, Doug. Thank you. So, Jason, when I do say mention that topic, what's the first thing that comes to mind for you about urban forestry and shade?

0:58SPEAKER_02:Yeah, I mean, for me, uh, you know, trees and heat uh are one of the most intuitive kind of benefits that we get uh from trees. Anytime you take people outside, start to talk about trees and uh the benefits they provide, people just intuitively walk and stand in the shade of the tree. We just know that that's where the cool air is. Uh and a lot of the work that Jay and I do are how do we take that uh kind of intuitive knowledge about the benefits of trees to cooling us off and turn it into data so that we can start to make better decisions about where to put trees so that they provide us with the most cooling benefits.

1:31SPEAKER_01:And Jay, tell me a little bit about the data. How is it collected and what are you collecting?

1:37SPEAKER_00:So for the input data, we're using things that define the landscape, such as land cover or impervious cover and tree cover as well. We look at the weather data from a nearby weather station like an airport that will have hourly um units of temperature, humidity, and rainfall, etc. And then we can put this all into the iTree cool air model, which is a spatial temperature model to model air temperature with consideration to vegetation and the urban heat island effect, given the inputs that are put into the model.

2:10SPEAKER_01:So, Jason, what does that tell you then uh with that kind of data? What are what are you getting from that?

2:17SPEAKER_02:Yeah, so one of the really cool outputs we get from that are maps of where the hottest and coolest spots are in cities, and we can overlay that with where the trees are. Uh, and uh some of the work we do is really cool. It'll tell you what the hottest hour of the day is and the impacts of trees on cooling you during that hottest time. So, really, you know, when you need that shade the most, uh, what are the trees doing for you? And we can map it over entire cities so you can see where those cool spots are, and then maybe where we need more trees so we get uh more shade.

2:48SPEAKER_01:Yeah, Jay, is that how it works? When you look at that data, you can make decisions on boy, we definitely need trees in this area.

2:57SPEAKER_00:Definitely, and those patterns will also show differently at different times of the day or under different weather patterns. So we might only see a one to two degree difference between, say, an urban park and an urban street with no trees on one day, but on a different day with higher wind, higher vaprotranspirative potential, we can see cooling up to 10 degrees difference between those two areas.

3:24SPEAKER_01:This questionslash statement is for both of you, but is it just an obvious thing that trees are a good thing for the city and they're going to cool things down? Or can you can you not say that? Can you say, no, no, that's not true. Of some places we don't want trees.

3:42SPEAKER_02:Uh yeah, I guess for the most part, I think it is that that more trees are better. Um, but there there are instances where sometimes trees, uh, you know, trees are taking some water out of the ground and they're putting it in into the air. So if we've got a really dense canopy, uh sometimes we can keep some of that humidity around longer than we want it to. Uh so you don't want to make always really dense canopies that might hold that uh hotter, wetter air uh for longer.

4:08SPEAKER_02:Um, but for the most part, we don't have enough trees to begin with, so we're not running into that problem in too many places.

4:15SPEAKER_01:What do you think, Jay? When I say that the trees are a good thing for the city and we need more of them. Is that uh a true or false statement?

4:24SPEAKER_00:That statement is true. And while there are caveats to that, like if you stand under a tree on a super humid day, you can sometimes feel like it's almost a little bit hotter and humid under there, like the air is getting stuck. And that can actually happen again with these denser canopies if we lose some of the long wave radiation that can go up from the surface, it gets trapped beneath the canopy layer in the ground. So humans can occasionally experience up to about one degree warmer temperatures under canopy, but these are such limited times throughout the year that the overall net benefit is going to be a reduction in temperatures when you need it, more than that increase in temperature.

5:08SPEAKER_01:Jason, who uses the data? Who gets presented the data?

5:13SPEAKER_02:Yeah, so I I should probably kick this over to Jay because Jay does a lot of work uh actually presenting this data and sharing it with folks. But one of the big projects we have is with the state of New York. Uh so they have some statewide data. They've got a map of their entire state. Um, and I'll let Jay kind of fill in the details on what that looks like.

5:33SPEAKER_00:Yeah, we have quite a few different partners that use the iTree cool air model. We've been working especially with state agencies. So the New York State Department of Environmental Conservation is a part of a 49-step extreme heat action plan looking at everything from expanding cooled corridors to expanding the funding for community sites and cooling centers to looking at green infrastructure and how we can model that to look at urban heat reduction.

6:04SPEAKER_00:So, another big interest in iTree Cool Air is we can model both the heat index and the wet bulb globe temperature at a six-foot height. So we can start to look at outdoor worker safety. For example, days where we have to take up to 45 minutes of breaks for every hour when it's greater than like 85 degrees of a wet bulb globe temperature. And we can start to look at how that might also change in future scenarios.

6:30SPEAKER_01:Jay, tell me about that term there. What did you say it was?

6:34SPEAKER_00:Wet bulb globe temperature?

6:35SPEAKER_01:Yeah, what does that mean?

6:37SPEAKER_00:So the wet bulb globe temperature is another way to express thermal comfort, whereas the heat index only takes into account the air temperature and the humidity. The wet bulb globe temperature is looking at how much solar radiation is also coming directly onto you. So if you're in a flat open field, you're going to feel more of a wet bulb globe temperature than you might in a city where you have buildings overhead.

7:00SPEAKER_01:So who you who is using iTree?

7:02SPEAKER_02:Yeah, so our user base is really broad. It kind of goes runs the gamut from academic researchers uh doing some some sort of high-level science to we've used it with uh fourth and fifth graders measuring trees around their school uh and the benefits they provide. But all across iTree, the real goal is to measure and account for the benefits the trees are providing. And we know that this heat impact is a huge one, and we're trying to get a better handle on how we present that uh to folks.

7:30SPEAKER_02:And and uh on the research front, some of those researchers using it just published a paper uh they estimated uh how trees mitigate urban heat island effects in almost 9,000 cities around the world. And what they found was that trees account for about 50%, offset about 50% of that urban heat island effect uh in these cities around the world. And it kind of runs the gamut um, you know, from high to low. But uh, you know, there's some really advanced research going on there, and it's how do we get that information back to uh folks in cities who can use it, decide where to put trees uh so they're they're gonna provide bigger benefits.

8:07SPEAKER_01:When you provide this data, are you recommending types of trees or that goes to someone else? You're just talking about the temperature and these these other uh factors.

8:21SPEAKER_00:Yeah, we'll take into account temperature, and the other large consideration we like to put into our projects is the socioeconomic aspect of it. So who are the people living there, what age are they, what ethnicity are they, what are their health concerns? All of these things drive how vulnerable they might be to heat stress. So this combined with the temperature, we can give maps and graphs and tables recommending areas for further studies, looking at maybe what types of trees might be most beneficial in the area, or how they can alter the landscape to plant more trees.

8:59SPEAKER_01:This is so positive, Jason. Don't you think you're doing a really good thing, or are you looking at it as more of a scientist? Like if I was doing this, I'd be like, oh man, we're actually helping. We're actually helping cooling down these cities, or is it more of a science thing, like you're not looking at it that way?

9:20SPEAKER_02:No, I think I think we what we try and do is we try and take that science and turn it into that delivery part. So, how can we help these cities with the science that we know? So, really, how do we kind of simplify it, package it up, and deliver it? And um, you know, what Jay was saying is is one of the really cool things that we get into with this uh heat island thing is that we see that you can have the biggest impacts in kind of underserved communities.

9:43SPEAKER_02:So where you have lower income areas, typically they don't have much tree canopy to begin with. And those people are more at risk. They're gonna be outside more, they're gonna be less likely to have air conditioning, all those sorts of things. So where we can show people maps, where we can deliver that science in a way that says these are the spots where you really need to do this, uh, and it's gonna have a huge impact. Um, you know, that's what we're trying to do with Dietry Tools for sure.

10:05SPEAKER_01:How about for you, Jay? Do you how do you feel about it?

10:09SPEAKER_00:Yeah, I think Jason uh worded it very well, translating that science to delivery. But I think where it can feel like we're genuinely doing good and making a difference is when we see the ultimate impact of projects where we might be replacing a bus depot that was a steel overhead structure going up to 110 degrees in the summer with five trees for the bus stop. So when we see impacts like that, that really makes it feel like we're doing good and helping to drive that science forward.

10:42SPEAKER_01:Well, that was my next question. Have you been able to see uh changes uh after you've presented data in certain areas, or it doesn't move that fast? It doesn't move that fast, unfortunately. Yeah.

10:56SPEAKER_02:But that's also one of the cases that we make, right? Is that we know that these trees are gonna take a while to grow. Uh, you know, so making sure that people know that to get these real benefits, you got to maintain those trees. You got to be out there and watering them when it's hot. Um, you got to make sure you get them through that initial establishment period, which takes three years or so. Um, so really kind of leaning into the importance of maintenance.

11:18SPEAKER_02:And you know, you talked a little bit about species, picking right species that are gonna grow, that are gonna get big. You know, you don't want to plant uh something that's just gonna stay really small next to a bus stop. You want to get it tall enough that it's gonna shade the folks who are waiting there.

11:31SPEAKER_01:And in general, it it's a tough place for trees, uh, an urban environment. And so that's what I was considering thinking about were what species is there a kind of a smaller list of species that do well under those circumstances? And I know that it's certainly got to be case by case, every every place you put a tree, it's gonna be different. But do we narrow it down because we do need something that's gonna be tough and uh we want it to survive?

12:04SPEAKER_02:Yeah, for sure. We we definitely do narrow it down, and and some of the cool stuff that's going on now is um, you know, looking a little bit at how the climate's gonna change. Uh, we know that most places are gonna get hotter, but a lot of them are gonna get drier or wetter. So uh there's a lot of research around, you know, can we start growing more oaks in our cities here in the northeast where we are, just because they're a little more drought tolerant.

12:25SPEAKER_02:They're gonna be a little more resilient to those higher temperatures. Uh so there's a lot of things like that that definitely go into those considerations. And uh there are other folks on our team and other folks in kind of the uh arborist world who get into more of that species-specific research for sure.

12:40SPEAKER_01:Jay, how did you get into this? Why does this job write for you?

12:44SPEAKER_00:You know, I was drawn early on in college to maps and to how we can take science and actually make it into usable public policy for individuals. Uh one of my first large projects was doing a big floodplain assessment for the state of Massachusetts, uh, Department of Conservation and Recreation. And mapping out those FEMA floodplains to the environmental justice-based communities were was a great exercise in showing me how much our most vulnerable communities are going to be impacted by climate change so much sooner than even places in our cities where we have more resources.

13:26SPEAKER_00:Um, so it's really just the culmination of delivering science to individuals and knowing that I understand that science, and maybe I'm not the best person to deliver that public policy, but I am very passionate on the uh climate change front and on the socioeconomic front, and I can present that data.

13:47SPEAKER_01:And Jason, tell me a little bit about your journey to your job.

13:50SPEAKER_02:Yeah, I started out uh not really wanting to be about around people a lot, Doug. Uh so I I I got into traditional forestry because I had you know visions of being uh riding a horse in the backcountry, but um uh eventually I made my way around to urban. And uh, you know, uh when we talk about urban forestry, the the only reason we define them as urban forests is because a lot of people live there. So, you know, it's how can we make these forests that that serve the most people?

14:17SPEAKER_02:And and I've been doing this for about 13 years now, and and uh just connecting with people and seeing how people connect with trees and seeing how uh folks build community around trees, whether it's tree planting or uh protecting the trees where they live and finding them important and valuable, um, has really been what's what's kind of kept me going and and drives me forward to keep delivering uh, you know, make sure people get the trees they need and are getting those benefits that trees can provide.

14:43SPEAKER_01:And I know the data is going to a lot of agencies, but if a homeowner was listening to this and they they did live in an urban environment, could they access the data? Would they know what to do with the data, or or is there something they can do with the data?

15:03SPEAKER_02:Sure. So so we have some simpler tools. We've talked a little bit uh kind of uh side from the side here about uh iTree, but within iTree, I have a whole bunch of tools. Some of them are really simple to use. We have one that's called MyTree. If you go to myTree.itreeTools.org, you can just put in the trees that are near your house and it'll estimate the ecosystem services they're providing. We're working now on getting some real specific heat stuff into those models, but it'll estimate how it affects like your heating and cooling bill.

15:32SPEAKER_02:Um, so you can get an idea of how much benefit you're gonna get based on the species you plant and where it is around your house. We try and really kind of simplify that down so that anybody can understand it. You don't need to know much about trees. Uh, you can even pick from just a handful of species we have in there based on what their leaves look like. So we do try and and convey it to folks uh in the simplest form possible that it's still gonna capture the bit the basics of that science.

15:58SPEAKER_01:Jay, what kind of other cool air data can people take a look at?

16:02SPEAKER_00:Yeah, so for our more advanced users, you actually can go on the iTree Tools website and navigate to the Research Suite page. You could download the data or the model, it's all open source and you can run it yourself on your machine. But for the more uh average person that just wants to see perhaps their current average temperature and how that might change under an increased or decreased canopy. We have a report on the Research Suite website called Evaluating Urban Canopies Role in Alleviating Extreme Heat that shows nationwide maps of the hottest hour from 2021 and how that would look under a minus 50% canopy cover and plus 50% canopy cover scenario.

16:46SPEAKER_00:So these are huge jumps, but it's a good way to start to understand where you'll actually see differences if you plant trees versus where there may already be a decent amount.

16:54SPEAKER_01:And Jay, do you ever think about this? Do you ever think about what you hope the data does for these communities?

17:03SPEAKER_00:Definitely. Uh, we hope that this data enables communities to know not only that they can plant more trees and that that will reduce their urban heat island effect and the warming effects of climate change in the future, but where to do that to have the greatest impact on the individuals living there.

17:21SPEAKER_01:And Jason, for you, what do you hope this data does for these communities?

17:25SPEAKER_02:Yeah, I hope it just gives them a little more information to make better decisions, uh, you know, kind of change some of those decision points so people decide to have more trees, decide that trees are a good investment and that they're useful parts of their community. Um, I think that's really, really what does it for me.

17:41SPEAKER_01:Well, that was fascinating. Interesting stuff. Uh, Jason and Jay, thank you so much for your time for explaining this all to us and for the good work you're doing. Thanks so much. Thanks, Doug. This was great. Thanks for uh giving us the time to share.

17:55SPEAKER_00:Thank you, Doug. Appreciate the time.

17:58SPEAKER_01:One of the reasons I love hosting this podcast is meeting experts like Jason and Jay and seeing what they're doing to help our communities to hear more stories like this. Tune in every Thursday to the Talking Trees Podcast from the Davy Tree Expert Company. I'm your host, Doug Oester. I want you to subscribe to the podcast so you won't miss a show. And I want to know what you think about what we're doing. Send us an email to podcasts at Davey.com.

18:26SPEAKER_01:That's P-O-D-C-A-S-T-S at D A V E Y.com. You can also click the link at the end of our show notes to text us a fan mail message. Your ideas could be on a future show. We would love to hear from you, and as always, we'd like to remind you on the Talking Trees Podcast. Trees are the answer.