(somber music) [Narrator] This ancient-looking creature is the pallid sturgeon.

Sturgeon have thrived in North America's open waterways for over 70 million years, but today, in the Great Plains along the Missouri River, infrastructure for flood control and shipping have compromised the survival of this species, and climate change may be making the situation worse.

The ecosystem is in trouble on the Missouri River.

It's not the pallid sturgeon is in trouble.

The Missouri river flooded very infrequently prior to us channelizing the river.

As we narrowed the channel of the river to deepen it for navigation, flood heights increased and flood frequencies increased to the point where we're at today, where in certain parts of the river it floods every year.

[Narrator] In 1933, the U.S. Army Corps of Engineers began building a series of dams in the Upper Missouri River Basin for flood control.

Then, the lower half of the river system was significantly altered.

The streambed was narrowed to a deep, serpentine waterway that sped up the current to keep sediment from clogging the navigation channel for the shipping industry.

The dams have generated enough energy to power more than 1.2 million households for a year, but the changes took a toll on the river ecosystem, including the pallid sturgeon population.

Over the years, it became rare to catch one.

What they were capturing was older fish, all older fish, never the small, young, juveniles, teenager type pallids.

And so there was a major concern about, are we going to have this population go extinct because we're not seeing natural reproduction?

[Narrator] Biologists were worried about what it meant if this fish that survived millions of years was struggling.

Those concerns kick-started a hatchery that raises pallid sturgeons from eggs and releases them into the river to keep the population going.

Scientists track them to learn where they go and what they do, to understand more about what the fish need to thrive.

There are a lot of pallid sturgeon in the river, they're just largely hatchery fish.

So, it's a stop-gap measure.

[Narrator] For the long term success of the species, pallid sturgeons need to reproduce naturally and grow in the Missouri without any help, and for that to happen, biologists think the fish need side streams of slow, shallow waters to grow up without getting swept up in a fast current or a catfish's mouth.

In other words, the fish need the very habitats that were eliminated by mega-engineering projects of the 20th century.

In order to help the pallids, in 1986, the Corps of Engineers began restoring historic aquatic habitats by purchasing land from willing sellers, but changing stretches of the river for endangered species hasn't been popular.

It came to a head after the region saw devastating floods in 2011 and 2019.

Some landowners sued the Corps, and won, arguing habitat restoration changed the floodplain and contributed to erosion and increased flooding.

I've been in meetings where busloads of people show up and say, my farm is not your laboratory.

[Narrator] And there could be another problem with the way the river has been engineered.

Flooding could get worse as the frequency and intensity of storms increase.

Rezaul Mahmood studied how the Missouri River has changed over the last 70 years.

We particularly looked at very extreme, really top 1% of the extreme precipitations.

So, we found that there is a change in frequency of those events, and also the magnitude.

They're more frequent and they are larger.

[Narrator] Climate change may prove the current river design isn't working for anyone.

Although we've put lots of things in place to protect infrastructure, protect homes along this river, ultimately nature can override some of that.

So not only for pallids, but how do we adapt for the human needs along this river system?

[Narrator] Gerald Mestl says in order to help pallids and mitigate flooding, another approach is needed.

Widen the river to allow more room for high water levels.

Such a massive undertaking begins with a hard look at today's Missouri River.

[Gerald] Yes, it will cost a lot of money.

Perhaps less than one flood's worth of money to do it completely, but have a system that will meet our needs today and for a long way in the future.

[Narrator] Getting there is a long shot, without conversations among people who depend on the river.

[Joe] One thing pallid sturgeon are teaching us is that there are solutions.

It takes a lot of effort, good science, and a lot of work with stakeholders.

We do that on the Missouri River, because of pallid sturgeon.