[dramatic music] - [Rossie] 2023 was the warmest year on record, and 2024, we'll probably smash that record again.

But in cities, the heat is not equally distributed.

Here's a map of my hometown of Durham, North Carolina.

The red areas can be as much as 10 degrees hotter than the blue areas.

And just looking at satellite images of those two spots reveals obvious differences: pavement and parking lots versus leafy green canopies.

But the obvious solution, plant more trees, is not as easy as you'd think, especially in cities, because trees aren't exactly the predictable pieces of infrastructure that we'd like them to be.

So in a future where every year breaks a new heat record, how do we nurture our best line of defense?

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.