- [Ben] Every time I'm out in the swamp, it's otherworldly.

When you see that mist coming off the water, it's almost like the spirits of the swamp are also speaking back to you.

- [Bryan] We're talking about something the scale of the Grand Canyon.

This is the largest block of coastal cypress forests in North America.

These cypress trees are incredibly important for protecting our communities from hurricanes.

They're almost indestructible, but there are threats to them.

- [Narrator] The Atchafalaya River Basin is America's largest river swamp and Louisiana's first line of defense against the extreme weather that threatens the Gulf Coast.

How does this swamp and its cypress trees protect us from hurricanes, and how can we protect them?

(calm music) (engine sputters) - When I'm on the water, it's a spiritual connection for me when I'm paddling.

When I watch that mist kind of just growing and dancing on the water, it reminds me of maybe the ghosts of these old cypress trees that we no longer have.

I love sharing it with other people.

We don't know what we've got right in our own backyard.

Our locals don't even appreciate it like they should.

- We have the largest wild caught craw fishery in the United States.

People actually live off the land out here.

We have 150 different bird species that either winter or migrate through or use the basin throughout the year.

And then it's very important for flood control.

This basin is built to help keep Baton Rouge all the way to New Orleans.

We take flood waters through this basin so that they don't end up in our homes and cities downstream from here.

This basin takes part of the flow of the Mississippi River and all of the flow of the Red River, but during flood times, this floodway gets kicked into action to make sure that it's taking its appropriate amount of water out of the river.

- I love photographing cypress trees, what it represents, it's resiliency.

It's such a strong tree.

It's so valuable to this place.

They're not just beautiful.

Without 'em, this whole area could be washed away.

- We have about 350,000 acres of coastal cypress forest here.

These trees are related to the redwoods, and they grow and they live for a very long time and get to be really big trees.

Hurricane Andrew, which was probably the biggest storm to hit this system, it came right up the Atchafalaya, and in the areas that were more your oak trees and and things like that in the higher ground, it was like probably an average of about 40% of those forests were knocked down up to about 85%, but in the cypress forests that start here and really persist to the south of us, it was like 1% mortality.

That's a huge deal because these cypress trees, they evolved in this environment and they're extremely resilient to hurricanes.

So what you want is as many of those trees to be as healthy as possible because those are the speed bumps for that storm surge and that wind.

It's just providing all that friction before it gets to our communities.

A couple things that's special about 'em is their canopy.

As the trees get bigger and bigger, they start to kind of self thin.

Lots of trunk, little canopy, and so they're not a big wind drag.

And the second thing is that those cypress knees are part of the root system.

It helps them survive in these flooded conditions, but it also helps anchor them down.

They're just very, very strong so that when a storm comes, one's not falling into the other, and they have just very little blow down as compared to other trees that we find in these higher elevation environments.

See this?

Really unhealthy.

Up here we're coming, you're gonna see it.

When you come around, you're gonna see it.

It's a really healthy stand of cypress right around this corner.

Like everything that's almost indestructible, there are threats to them.

A cypress forest needs to survive as it needs two things, the water levels to be able to be such that little sprouts can grow up high enough and the water can come in.

They can be underwater, but they can't be underwater too long, or they drown.

The second thing that they need is they need good oxygenated water that comes from the river that gives them some fertilizer like some nitrogen to help them grow and be healthy.

I call this system sort of a hybrid wild system.

It has this sort of wilderness feel to it because it's remote.

There's so much engineering that's gone on so that this basin provides flood control.

So some of the consequences of that engineering are just a large scale disconnection of the water in the river from the swamps that need that water to sustain them.

And so what we get is times of the year when maybe the water is too high for what it would be naturally for, let's say, cypress and tupelo regeneration, or the water can't get into the swamp, so the fish species that need it and the crawfish that need that water interaction don't have it.

We get stagnant water for long periods of time.

The oxygen drops out.

We have fish kills.

The trees get stunted because they're sitting in that low oxygen water for large portions of the year.

You can see how high this bank is here.

Many years, water will come up, but it's not high enough to get over this bank.

Takes like a really big flood to get water up over this bank.

The work that that the Nature Conservancy and that our team is doing out here, it's part of something we call the Atchafalaya River Basin Initiative.

We have a preserve out here that we could potentially have the ability to restore more natural water flows, to promote cypress regeneration and provide good water quality for cypress to grow.

We're working on fixing some of that broken plumbing that we have out here on our 5,400 acre preserve and surrounding state-owned lands by reestablishing that connection between river flow, allowing water to get into the swamp on a normal basis and then get out of the swamp.

- The swamp is not an easy environment to recreate in.

And so when you go out here and you experience it firsthand, you get the chance to paddle through these waters.

You're a changed person when you're done.

And that's what we love so much about introducing people to this place.

- We have the scientific body of knowledge.

We have the engineering know-how to help us ensure that this basin is resilient for not only the fish and wildlife, but for the people who depend on it for their livelihood and to protect them from hurricanes.

(calm music) (calm music continues)