- [Narrator] North America's relationship with the beaver has been somewhat tumultuous.

Starting in the 1500s, humans almost eradicated them from the continent for their fur.

But when we did that we fundamentally altered the landscape because it turns out beavers are one of nature's most prolific engineers.

- When it comes to beaver there are kind of two main camps about beaver people either, oh, love them, people like me, they're a keystone species, an ecosystem engineer.

They are important.

They have this huge role in the landscape.

We should love and appreciate them.

And then there are people who see them as 70 pound rats who flood their yards and they needed to be relocated and gotten rid of.

- [Narrator] Nuisance or not, the wetlands and ponds made by beavers create habitat for countless other creatures and protect ecosystems from devastating wildfires.

Today there's a movement to bring beavers back and restore what we lost when we almost ousted the beaver from our world.

But first, researchers have to document the difference that beavers are making.

That's why UNC Chapel Hill scientists are studying beavers in urban watersheds including the Ellerbe Creek in Durham, North Carolina.

Because believe it or not, beavers do exist in the city.

Take this beaver pond behind Compare Foods.

But humans also build ponds.

Urban landscapes are dominated by retention ponds.

They're there to control water.

- When you pave the landscape, then there are other problems and those problems are flash floods.

So every time it rains, water's not infiltrating but just running over over the parking lot or over the road and it moves very quickly.

The retention ponds are built to take the energy from the water and store that water in different places.

So if you look at new development, for example, nowadays the first thing they do is they take down some acreage of forests.

They put roads and they build the retention ponds.

- [Narrator] Retention ponds might not always be pretty but they work however, they come at a cost.

- So there's lots of concrete that goes into it.

There is the plowing.

There is like everything that takes place to build these massive structures.

And then cities have to manage 'em.

They have to clean them so that they function properly and they function for decades as intended.

- [Narrator] Beavers are controlling water too but they're doing it for free.

- So my little elevator pitch is that we are comparing bio retention ponds and beaver ponds because if you think about it they're really almost the same thing in structure.

There is water coming in.

That would be a single flow but then there is a dam that stops it and it just varies by retention ponds.

A human put that dam in there.

That beaver pond a beaver put the dam in there.

- [Narrator] But let's back up.

Why are beavers doing this?

Why are they always making ponds?

Beavers build dams so they can have a deep enough pond for their lodge.

A dome shaped home to stay warm and protected from predators.

They access the lodge using a tunnel beneath the water.

Some of these dams are impressive including this half mile long one in Canada that you can see from space.

The downside of beavers is that sometimes they make ponds where you don't want ponds but they're considered a keystone species because they create so much habitat for other wildlife.

Things like frogs, fish, and vertebrates which in turn feeds larger mammals and birds.

And then there's the benefit to us.

In some places beavers are storing enough water to protect areas from wildfires and severe droughts.

Problems that are only getting worse with climate change.

All these benefits are giving researchers the incentive to study beavers more closely.

- How do we manage them in a way that is sustainable that is providing an ecosystem service to us?

And it really, it will have to be studied on a case by case basis.

- [Narrator] The team is trying to find out if beavers can do a better job than retention ponds at cleaning and filtering the water.

So they're taking lots of measurements that compare the two including one that measures the ability of both types of ponds to break down nitrogen and phosphorous.

Nutrients that cause deadly algal blooms.

They're still collecting and analyzing data but one thing is certain, beavers are amazing free labor.

- Mean, if you think about it, we're spending so much money to build this bio retention infrastructure and we're spending so much money to relocate and hunt beaver, but they're doing the same thing.

So I think, even for people that don't see them as cute, adorable creatures if you can see it from a logical perspective of, oh maybe it would be worth taking the time and energy to use these to our advantage.

[whimsical music]