This lesson includes a collaborative project in which your group will be asked to produce a presentation or other media project that defines the issue of urban heat islands, stresses the importance of addressing their dangers, and describes reasons and methods related to planting trees as potential solutions.
Before you begin that collaborative, take a chance to organize the notes you took on the three broadcast video excerpts you viewed earlier in this lesson. You can do so by clicking on the Organize It box, below, and following the prompts.
For your convenience, the broadcast videos and transcripts are posted at the bottom of this page.
Organize It!: Your work has been submitted.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
[Narrator] Ah, the urban jungle.
Except, it generally has a lot more concrete than an actual jungle, and that makes it hotter.
- The science behind it is relatively simple.
On a sort of 10,000-foot level, hard surfaces tend to be hotter.
Dark surfaces tend to be hotter.
Soft surfaces tend to be cooler.
Shade tends to be cooler.
Unfortunately, within built environments, within these urban areas, we have lots of areas where we have lots and lots of impervious, hard, dark surfaces that hold onto heat, and make those areas very, very, very hot.
And we have fewer areas with green space and shade, that tend to be cooler.
And because these two can be really close to each other, you can see huge amounts of variation.
Sometimes 15 to even 19 or 20-degree differences between areas within the same city, on the same day.
- [Narrator] We call these hotspots urban heat islands.
And with global temperatures on the rise, that heat can turn deadly.
- Heat is our number one weather-related killer.
And we often don't think about that.
We see the floods, we see the hurricanes, we see the fires on TV.
It's kind of hard to show heat on TV.
But we know that a lot of people die in days with extreme heat, and also nights that are extremely hot.
We already have hot parts of the city, historically.
And we're adding a few degrees more warming to that, and we know they're just going to get more unbearable.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
- [Narrator] There's a lot of weather data available.
You can easily access a prediction of what your week is gonna be like, sometimes down to the hour.
- But the data that we have to measure temperature is from our cell phones, from weather stations.
That data is very sparse, and it represents generally large areas.
As we walk through an urban area, we may go under some trees, and it's really shady and cooler.
We may walk across that parking lot surface, it's much hotter.
We experience temperature variably throughout an urban area.
The problem is, is that the existing data from weather stations is not fine enough to actually measure those differences.
- Let's go attach this to your car.
- Yeah, let's do it.
- [Narrator] To better understand the true exposure and experience of heat in Raleigh, Durham, and Chapel Hill, the Museum of Life and Science partnered with local organizations and communities to take on the ground measurements of heat, in the summer of 2021.
- [Max] So this project is a little bit different from perhaps a traditional scientific study in that so much of the data collection, and then a lot of the analysis afterwards, is going to be done, and publicly owned and available, by the people that live there.
- It's really important to know that anybody can be a scientist.
You don't need a PhD to do science.
So what we're trying to do is empower these community members to study their community.
And hopefully with these data, then they can enact some policies, or plans to help mitigate their heat stress - [Narrator] Routes throughout the cities were developed with community input.
And then volunteers carried sensors along those routes three times during the sampling day, morning, midday, and evening.
Data was collected by a car, by bike, and on foot.
The data collected painted a powerful picture.
- The data did indeed show that there were urban heat islands.
It also found that there are existing heat disparities on that neighborhood by neighborhood, or sometimes block by block level.
July 23rd was around 88, 89 degrees, which is pretty much the typical summer day that you'd expect here in central North Carolina.
On that day, in the evening, we reached a temperature difference of about 11 degrees, which is a pretty remarkable finding.
It means that within our study area, and indeed here in Durham, some neighborhoods, sometimes only miles apart, were 11 degrees warmer than neighborhoods that were close by to them.
A lot of what we have found is that if you live in an urban area you're not just doomed to live in a warmer area.
There are pockets, individual small level areas, that are warmer than other parts of the urban area.
- [Narrator] UNC Chapel Hill's data driven Enviro Policy Lab facilitated a hackathon, where people dug deeper into the data.
- The idea of a data science hackathon is to open up the data, get mentors, people who are climate scientists, or have some knowledge about urban heat, or public health, and get people together to try to come up with creative solutions, data analysis, visualization, to help better understand the problem of urban heat exposure, and what we can do about it.
Globally, 65% of people will live in cities by 2030.
And that number will just continue to increase over time.
It's gonna become an increasingly important issue for citizens and policy makers to be aware of, and to do something about.
- [Max] Equitable planning, to make sure that we are not only dealing with these urban heat islands, but also dealing with it in a responsible way, means making sure that we include residents in the phases of planning, so that whatever happens in these areas is led by their priorities and their preferences.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
The first rule of an urban forest: right tree, right place.
- So this is an interesting tree.
It's a bald cypress, which you don't see in cities nearly as often as some other species.
But one of the reasons it's planted here is 'cause it can tolerate really wet conditions super well.
And we're right by a stream, which makes perfect sense.
So you plant a species like this in the right place and it does super well.
If you planted a tree that needs to be really dry here, not nearly as good, and it probably wouldn't be nearly as healthy as this one.
- [Rossie] Renata studies urban forests at Duke University, they know the trees in downtown Durham intimately.
And we took a tour to see some happy trees and some not so happy trees.
- So in the last decade, two decades, there's been a lot of emphasis on planting trees 'cause we realize the benefits of them.
And immediately, one of the problems that came up with some of these Million Trees initiatives, for example, is where do you put them?
So in cities like Boston, for example, they have smaller sidewalks in some of these older neighborhoods.
And if you wanna make sure that your sidewalks are accessible to, say, people using wheelchairs, you put a tree in the middle of your sidewalk, a wheelchair can no longer go through.
One of the other things we find is a general idea of right tree right place is really important.
So if you're planting a redwood, which I have seen planted in a very, very small planting space, it's gonna pull up your sidewalk.
It's gonna cause problems, just because it's a big tree, right?
- [Rossie] Also, tree lovers are quick to point out the benefits of native trees.
They're adapted to the region's climate and many species provide food for native wildlife, but natives aren't always the best fit for urban environments.
Trees die younger in cities.
They're surrounded by concrete and there's not much room for their roots to grow.
- And the species that tend to handle urban conditions really well are not always the native species.
So things like ginkgos.
Cool tree, a lot of cities have some of those ginkgos, they're not native to anywhere in the United States.
- [Rossie] Take this lace bark elm, which is a non-native tree in North Carolina.
It can handle the compacted and low quality soil here and it doesn't require much maintenance.
- Notice here we've got construction on one side.
This is all brick and paved over, right?
It is a very stressful place for a tree.
So you need trees that can handle these kinds of conditions.
- [Rossie] The second rule of urban forests, you need the community.
Cities like Durham are leafier than most.
We have a 52% canopy coverage.
Other cities, it's more like 20%, but crucially, more than 90% of that canopy is owned by residents.
So it's up to regular citizens to maintain the trees, and the places that the city can plant trees are limited.
- So in Durham, for example, one of the places that the city can plant trees is in what's called a right of way, or basically an area that is technically public land, but often looks like it's on somebody's property.
And if you're a homeowner minding your business and suddenly a tree pops up in what you think is your property, that can be kind of surprising.
And if you're excited about that, maybe the city talk to you ahead of time, then great, right?
Then you can water the tree, work with the city to take care of the tree and it might do great.
But if you're not expecting it and you may not be excited about it, 'cause you had other plans for that space, then you can have tensions and that tree might not survive as well.
- [Rossie] Getting community buy-in means building relationships with groups that have been marginalized.
It's no coincidence that the hottest areas on this urban heat map are also the same historically Black neighborhoods that were redlined in the 1930s.
These areas were officially designated as risky investments.
And the city planted far fewer trees along sidewalks and roads.
Today, wealthy Durham neighborhoods have 50% more canopy coverage than the redlined neighborhoods.
It's the same story in many southern cities.
But Renata says that solving those past inequities can't happen without community buy-in.
- Is there a plan to take care of these trees for the next 20, 30, 80 years, depending on the age of the tree?
Or are you expecting residents to do that?
Because in some cities it's the resident who has to take care of it.
And if you're already strapped for money, the idea of several hundred or even more dollars they have to spend regularly is not exactly exciting.
Or they had other plans or uses for that space.
If the kids generally play a soccer match on the edge of the road in one person's yard and you put a tree in the middle of it, that may not be exactly what the community wants.
They might want a tree somewhere else, but right there, it may not be exactly what makes sense, 'cause even if you do plant trees, I'm not sure they're gonna do super well if the people aren't excited about them.
- [Rossie] And that leads us to the third rule of urban trees: they require care.
- Water is really important for the first two to five years, or really the first five years of a tree's life post planting.
And it's great if you can come by with a water truck, but it can be more reliable to have something like a gator bag or a... Oh, what is this called?
I think they might call it a tree diaper, to be honest, which is kind of funny.
- [Rossie] Young trees often get damaged by construction or even routine lawn maintenance, like this little red bud that is still against all odds alive.
- [Renata] If you get closer, you'll see the wood path probably happened as it got hit.
Even if you do everything right, especially with young trees, they still don't always make it.
- [Rossie] And sometimes trees grow in places you might not expect or even want.
Though I happen to love this one.
- Trees are still living things, and at the end of the day, they will do what they want.
A tree will not grow always the way you want it to.
It won't always look the way you want it to.
And that's something you have to plan for too.
That we are living with other living beings, not just some slab of concrete.