- Hi there, I'm Frank Graff.

How to solve the problem of urban heat islands.

Could glassy gels solve the plastic waste problem?

And giving gopher frogs a better chance to survive.

We're problem solving science, next on Sci NC.

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- Sci NC is supported by a generous bequest gift from Dan Carrigan and the Gaia Earth Balance Endowment through the Gaston Community Foundation.

(upbeat music) ♪ - Hi again and welcome to Sci NC.

An urban heat island is defined as the relative warmth of a city compared to the surrounding urban area.

The heat trapping from land use, that makes total sense.

But as producer Michelle Lotker explains, researchers are discovering new ways to ease the heat island effect.

- Summers in the South are hot, but just how hot?

You might look at the temperature for the day on your phone or listen to the news to find out what to wear, but that information is usually coming from a weather station that might not accurately represent what you, a human walking around at ground level, experiences.

It is so hot today.

This is especially true in cities.

- The location of current weather stations, which is how we get air temperature, they're often actually not located within a city.

They're more located in airports.

What that means is we don't actually know what the temperature in a very urbanized center is.

- And that's especially important when it comes to heat.

- A lot of people call heat stress the silent killer because not a lot of people really think about it as a weather-related disaster.

But when there is a heat wave, a lot of people can die from it.

- Researchers in North Carolina are trying to paint a more detailed picture of what humans experience when it comes to heat in urban environments by measuring air temperature at around two meters or 6.5 feet off the ground.

They're doing that with these tiny sensors, starting with Durham, North Carolina.

- Durham is a good place to look at urban heat stress because there's such a wide variety of urban forms.

So we have parks, we have really built-up city centers with a lot of concrete, and there's also a wide variety of socioeconomic categories.

So we can really do a lot more meaningful work.

- This study used 41 sensors spread across the city to cover a variety of different location types based on land cover and solar impact.

- We had two different land cover types.

So we had vegetated land cover and we had impervious land cover, which is essentially surfaces such as concrete and asphalt.

And then the other two categories within that were shaded and unshaded.

- This is one of the vegetated shaded sites near Indian Trail Park in North Durham.

- So Christian has just connected to the sensor via the Bluetooth link on his phone.

- It's showing temperature, relative humidity, heat index, and the dew point.

So all measures of air temperature.

- This is a radiation shield, and it's initially what you see with the sensor.

But if we actually take a look inside, if you look in this little window here, that is the probe.

So the air in this little window here is what we're measuring.

Now, if we didn't have this radiation shield on the sensor, in places where it's not shaded, like this location, what you'll actually be measuring is the heat from the sun heating up that temperature probe in the middle.

So it's really important for us to have this to protect it and also to make sure that it's measuring air temperature.

- And looking at what the probe is currently sensing at the site, there's evidence of the differences in what a human would experience versus data coming from the regional weather station.

- It's 73.8 degrees Fahrenheit, according to the sensor.

But if you look at your weather app, it's currently 78 degrees.

So this is a little bit more of an in-depth measure of the cooling effect of shaded or vegetative shading.

- The same morning at an unshaded site surrounded by impervious surfaces, the opposite was true.

- We're currently at the Hayti Cultural Center.

We're actually about one minute outside of downtown itself.

In contrast to the vegetative shaded, we consider this one impervious unshaded.

- We've driven only for about eight minutes' drive to this spot, and already it just feels a lot hotter.

- So the temperature at this site is 81.7 degrees Fahrenheit, which is interesting because the weather currently says that it's 80 degrees now.

I mean, these metrics basically show that the urban heat island effect is very much real.

Lack of shading and ultimately lack of vegetation does induce the urban heat island effect.

- The fact that you have some areas which are warmer than others and those aren't being represented by the current data, it just means that it's something that we really need to understand a lot better.

- The sensors recorded air temperature every 10 minutes for two months.

Back at the lab, the team is digging into all that data to paint a more detailed picture of heat impacts across the city.

- Some of the things we're seeing were things that we expected.

The vegetated surfaces are cooler than the impervious surfaces.

If we kind of zoom into the map a bit, you can see that one of the cooler areas here, this is located in a really forested, vegetated area.

If we find the warmer points here, for example, they're located in an area with a lot of roads and a lot of buildings and not really a lot of green spaces or parks around.

- Looking at average minimum and maximum temperatures reinforces the effects of vegetation on heat experienced.

- This is the maximum temperature.

The Hayti Center is 92.4 versus the Indian Trail Park, which is 87.4, so it's quite a bit warmer at the Hayti Center.

- But there are a few surprises as well, especially looking at nighttime temperatures.

- If we look at the nighttime area, which is this left-hand side here, the black line is actually higher up than the yellow line, which means that the shaded surfaces are warmer during the nighttime than the unshaded, which we believe is down to the fact that when the ground heats up during the day, during the nighttime, it radiates that heat out and it's actually trapped under the shaded canopies.

That's an interesting result, which could mean something for nighttime temperatures.

Especially since hotter evening temperatures have been shown to increase negative health impacts related to heat exposure.

The sensors have added to what we know about Durham's heat landscape, but they still only represent their specific locations.

Using machine learning allows the team to paint a more complete picture.

The 4D sensor is just a starting point.

With this 4D sample site as the training data, we use machine learning models and combine it with the remote sensing data to build a machine learning model which can predict for the area we don't have sensor covered.

The remote sensing data comes from satellites and shows land cover type at a scale of around 100 meters square.

Here you can see a satellite photograph paired with the remote sensing data that's used to tell the model what kind of land cover is present in an area.

On the left side, this is our machine learning model for our max temperature of July and August last year.

And on the right side is the land cover types.

These two map patterns are kind of similar and that is true because the land cover data is actually part of input variables for our machine learning model.

Since land cover is known for the whole city, the knowledge gained at sensor sites can tell us about other parts of Durham.

This is the boundary of Durham and all those yellow dots are where we install the sensors.

When we bring in the machine learning and remote sensing data, we're able to extrapolate from this 4D sensors to all over the place in Durham.

Remote sensing is helping us to fill in the gaps and figure out what happened in the area we couldn't measure.

Why do we need to know how parts of a city are experiencing heat in more detail?

It kind of comes down to how policy makers can actually use this data and shape new urban policies or environmental policies for the state to counteract areas that might be experiencing more heat stress compared to others.

By working with local organizations to determine sensor sites and incorporating socioeconomic information to interpret the data, the team is hoping what they collect and extrapolate can have meaningful impact for people living in the city of Durham.

Cities are less than 2% of the Earth's surface, but they're where the majority of people are concentrated.

So by 2050, about 70% of the world's population is going to be in cities.

So this is why it's really important for us to actually know how the people in cities are going to be affected by heat stress now and also in the future.

- Now a question.

How many times do you do this?

You finish using that hard piece of plastic that was needed for something, and then you, thank you, throw it away.

It's why the world is struggling to deal with the flood of plastic trash.

But as producer Evan Howell explains, scientists at NC State have found a way to turn hard plastic into a stretchy gel that can be reused, and that might reduce the amount of plastic waste.

- Hungry?

Just add water to this powder, stick it in the fridge, and after a bit, you've got some jello.

You're happy.

But what if you thought like an engineer?

What if you were thinking about taking that jello and making it tough enough to where it stretches to five times its size and make it really strong?

Well, these scientists discovered how to do that by accident.

- We weren't trying to necessarily solve a problem.

- Researchers at NC State are creating a material that's soft a bit like jello, but virtually as strong as the hard plastic in the water bottle you use every day.

It's called a glassy gel.

It's a discovery that could transform industries like 3D printing and soft robotics.

- So most common plastics that you encounter in your day-to-day life, like a water bottle or these glasses that I'm wearing, tend to be hard.

And we call those glassy because the polymers that are in those materials are sort of stuck in a particular shape.

- A glassy polymer like that water bottle is hard and solid because its tiny pieces can't move.

A glassy gel is like firm jello, mostly liquid but stuck in place by a solid sponge.

That's where liquid and solid work together.

At first, Dickie's team was simply looking at materials that go into a wearable technology and could sense body movement and heat.

But they started to see some strange stuff going on.

- Normally when you add liquids to plastics, they become very soft.

And so that's when we had our eureka moment.

- They discovered a special ingredient that made these hard materials soft, but kept them strong, ionic liquid.

- Gels are all around us also.

So there's things like jello, for example, or tofu, or even our bodies.

And these are, again, polymers, but they're surrounded by liquid, typically water.

And they have very different properties, namely they're stretchy.

- And they found a special sauce that changed the equation.

- We think of it as a recipe where we have these ingredients, like this ionic liquid here.

- The materials are filled up with 60% of this ionic liquid, which is a salt solution that stays liquid from room temperature up to 200 degrees.

And that gives it the advantage.

The ionic liquid interacts with the polymer and spreads the polymer chains apart, making the material flexible.

But that ionic attraction holds those chains in place, giving the material that harder feel.

- It's very much like a towel where we have water kind of soaked up into this material.

So this one has a lot more water than this, so it's much more stretchy.

So they were originally the same size, but since they have water inside it, more water inside it, it's become swollen.

- The best part, Dickey says, is that the material is easy to make.

Maybe not like Jell-O, but simple in a lab.

Once those ingredients are put together, the material is placed between glass like you see here.

Last step in the recipe is to put it in the oven and bake it all together.

- It's UV, and the UV causes the liquid to polymerize and form the glassy gel.

So it goes from being a liquid into being a solid.

This process depends on how bright the light is, but it typically just takes a few minutes.

- These glassy gels are sticky, and Dickey says they could have applications in adhesives, window insulation, because they don't dry out, overheat, and are simple to make.

One of the things they're looking at is making what he calls biocompatible.

- Contact lens, if you leave it out, it will shrivel up and become very hard and dry because the water evaporates.

This doesn't do that.

- There are even applications in the power industry, like batteries.

Since salt is a conductor, these materials can conduct electricity, and since they're hard to break, they can reduce fire risk.

- Plastics are sort of all around us, but they tend to be made in factories.

We wouldn't be able to make a lot of the plastics that you find in this lab.

We wouldn't be able to make them here very easily, but this material, we can.

We literally just mix them together and shine light, and that's it.

- North Carolina's pine forests are home to lots of unique species, including the endangered gopher frog.

Producer Michelle Lotker takes us to the Edenton Fish Hatchery, where biologists are helping these tiny frogs get a head start before they head into the forest.

- These gopher frogs are endangered, but at the Edenton Fish Hatchery in North Carolina, they're getting a helping hand.

Biologists there are working as part of a team to raise these frogs outside of their natural habitat, which is not as available as it used to be.

- Part of the reason that they're in trouble is that they rely heavily on longleaf pine forests to survive.

They live in the burrows of longleaf pine trees that have died due to fire.

As their roots decay, they leave a network of burrows, and that's actually why they're called gopher frogs.

They spend over 90% of their life, 90 to 95% of their life in those burrows, and then the only time we get to see them is when they come out to spawn.

- In addition to working to restore habitat, scientists are trying to give the existing population a boost by increasing the chance that some of the eggs in the wild make it to adulthood.

North Carolina State Aquarium and Wildlife Resources Commission staff collect egg masses from the wild, leaving 90% behind to hatch naturally.

Once those eggs hatch, they're spread out to places like the Edenton Hatchery to grow into adulthood.

- We're kind of like a safe haven, right?

So we protect them by providing a headstart, safe space for them, because this is the most vulnerable time in their life.

- At the Edenton Hatchery, they've created these tanks to mimic the ponds the frogs will spawn in in the wild.

And these small worlds, or mesocosms, are where the tadpoles grow up.

- These are the mesocosms that the tadpoles are raised in, and they've been in here since mid-March, and we put traps in there.

As you can see, there's some in the minnow traps.

- Minnow traps help to collect the adult frogs as they metamorphosize from legless tadpoles.

But biologists at the hatchery still have to sort the frogs to select only the ones ready to be re-released to the wild.

- We'll harvest them throughout the day.

More of them will be in the traps in the morning.

And if they have a tail, like this little guy, they have to go back in and reabsorb them.

- Look at that tail.

This one definitely isn't ready yet.

- Anything that has less than a quarter inch of tail is okay to keep, but if there's much of a tail at all, then it goes back in to cook a little longer.

- Here's a tadpole.

Here's one with no legs on it yet.

- These were harvested from different egg masses at different times, so that's why there's differences in the development of each of these.

- If they don't have a tail, then they come out of the traps, go into a bucket, and they'll go and get weighed.

- The hatchery has weighed over 260 gopher frogs that are ready for release so far this season, and it's only June.

- Okay, so let me just explain what I'm doing.

So what I'll do is pick the frog up, put it on the scale.

I'll initially hold my hand over it while I'm weighing them, and then I'll put the lid on it so that I can put them in this container.

The main thing with this part is creating a system and doing the same thing every time because when you're weighing 75 frogs, it's easy to get distracted.

- So these are the frogs that are graduating from our Head Start program.

- Frogs that are ready for release are tagged and then brought back to their home turf.

These came from Holly Shelter game land, so Wildlife Resources Commission biologists will be re-releasing them there.

- Since there's only about 200 to 300 known adult frogs out there, that's an estimate, then we're just concerned that even with the improvements that people are trying to make to their habitats, they're just not gonna make it.

So we're just trying to give them a boost to the population.

Hopefully this is just a temporary situation and they'll be able to handle the populations, be self-sustaining without our help.

But for now, we're just kind of giving them a head start.

- Still in the forest, our last walk in the woods for this season takes us to Raven Rock State Park, where hundreds of thousands of years of erosion by the Cape Fear River carved the park's namesake, a 150-foot crystalline rock formation.

- Andy Wood is taking us to a place where the three ecozones of North Carolina seem to converge, the Coastal Plain, the Piedmont, and the mountains.

And in this place, we can explore how, with time, small things create dramatic results.

Andy, where are we?

- Raven Rock State Park in an area where the Piedmont of North Carolina meets the Coastal Plain of North Carolina.

- And I know we're here to see the park's namesake, Raven Rock, but there's also a tree that we're after.

What's special about it?

- It's an American beech that is growing on top of a mound part of this Raven Rock, and it literally is breaking that rock apart with its roots.

- You're gonna have to explain how that's possible.

- Soon as we get there.

- All right, let's go.

- We're in a transition area in the state of North Carolina where the Piedmont of North Carolina meets the Coastal Plain.

And in this zone, we find such things as mountain laurel.

- Here at Raven Rock, the mountain laurel has its own microclimate, thanks to cooler air blowing off the Cape Fear River and up the rock face.

It's nature's air conditioner, according to Andy Wood.

I mean, it's got mountain in the name, so it should be-- - In the mountains.

- What other kinds of unique species would we find here?

- Well, I can hear lots of birds, and this is springtime, so we've got lots of songbirds coming up from Central and South America, warblers especially, colorful, beautiful little songbirds.

- More than one kind of warbler?

- Oh, in Raven Rock State Park, this time of year, you might be able to get 20 warblers in a good couple of birding days.

And they're here because these trees support the caterpillars that they really like to eat this time of year.

- Obviously, birds aren't the only creatures feeding on the spring caterpillar bounty.

This is, of course, one example of a predator-prey relationship.

It's ubiquitous in the animal world and easy to find there, but this relationship is also one of the pillars of life on this planet.

Soon, we'll see a striking example between a plant and a rock.

We're looking across the Cape Fear River.

Are we looking at the difference between the coastal plain and the piedmont?

- Perfectly, yes.

- Raven Rock State Park came into being because one local man believed this breathtaking natural beauty should be preserved.

Campbell University professor Robert Sootes heard rumblings a corporation might buy the acreage for industrial purposes.

So he worked first with Harnett County and then the state in the late 1960s to create the park.

More than 50 years later, the park and the rock stand as tangible examples of the power of individual activism.

You explained that this beech tree is growing out of a rock, but when we first look at it, it looks to me as if it's growing on top of a rock.

- It started growing on top of the rock, and over time, its roots have grown into the rock, and now it is disassembling the rock.

- How is it possible?

How can a tree root penetrate a rock?

- So the rock has little cracks in it, and they may only be millimeters wide, tiny, maybe even the width of a sheet of paper, but the tip of a plant root is only a couple of cells wide.

So it can slide into that little bit of a crack, and as it grows, eventually crumbles the rock.

- Hmm, not unlike the ant attacking the caterpillar.

This exposed root system, though, isn't just because it's on top of a rock.

According to Andy, human foot traffic has prevented leaf litter and dirt from covering the roots.

You called this a formation.

It looks like a rock outcropping to me.

So how did this form?

This is really dramatic.

- It's only exposed here because of the Cape Fear River, which has eroded away the topsoil that separates this rock from the coastal plain just across the river.

So this is where the hard, what's called nice rock, G-N-E-I-S-S.

- Nice.

- Pronounced nice, Gneiss is what it looks like.

And the coastal plain, the rock in that region is softer than this.

This is a hard rock.

- So you're saying, I just wanna make sure I understand this, that we're seeing this kind of sheer cliff face, if I can call it that, because water has cut through it.

So how long would it have taken for this rock outcropping to take the form it's in today?

- Hundreds of millions of years.

- If some microscopic tree root cells can burrow into hard rock and grow into an imposing beach tree, if water can cut through metamorphic rock over hundreds of millions of years, if one man's appreciation of nature can supersede industrial expansion to create Raven Rock State Park, then what power might live in our own tiny, as yet unexplored ideas?

- And that's it for Sci NC for this week.

If you want more Sci NC, be sure to follow us online.

I'm Frank Graff, thanks for watching.

(upbeat music) ♪ ♪ - Sci NC is supported by a generous bequest gift from Dan Carrigan and the Gaia Earth Balance Endowment through the Gaston Community Foundation.

- Quality public television is made possible through the financial contributions of viewers like you, who invite you to join them in supporting PBSNC.