GEOFF BENNETT: Near the Chesapeake Bay, farms have flourished for hundreds of years on the rich, fertile soil of coastal Maryland.

But as sea levels rise, driven in part by climate change, encroaching saltwater is quickly disrupting the lives and livelihoods of many farmers, a preview of what other farming areas near saltwater may soon be confronting.

William Brangham reports for our ongoing series on climate change and water, Tipping Point.

KEVIN ANDERSON, Somerset County, Maryland, Farmer: When I bought this farm, this field was perfect.

Now the tide comes in and out of here all the time.

WILLIAM BRANGHAM: Kevin Anderson's farm near Princess Anne, Maryland, is now plagued by saltwater.

KEVIN ANDERSON: And this area that we're standing here now, in the last 90 days, I would tell you it's had water on it at least half the time.

WILLIAM BRANGHAM: This cornfield is nestled near a creek connected to the Chesapeake Bay, and, a decade ago, he says that saltwater mostly stayed in the creek.

But now it's increasingly coming onshore, making some of his land completely unfarmable.

KEVIN ANDERSON: There's an acre of corn right here that cost $650 an acre to grow that I won't make a dime off of, because nothing productive will come from that.

WILLIAM BRANGHAM: About 30 miles away, a group of researchers who study sea level rise and saltwater intrusion, as this phenomenon is known, are trying to help farmers find solutions for what could be a potentially existential threat from all that saltwater.

The University of Maryland's Kate Tully is one of the conference organizers.

She studies the connections between agriculture and ecology.

KATE TULLY, University of Maryland: When we have this concept of climate change, we kind of think of it as something that's going to happen.

And what we were saying is, it is happening.

WILLIAM BRANGHAM: The Delmarva Peninsula, bordered by the Atlantic to the east and the Chesapeake Bay to the west, is experiencing sea level rise at three times the global average.

That's driven by climate change, but the land here is also slowly sinking.

As a result, low-lying farmland is being lost at an alarming rate, as saltwater continues to flow onto the land from storms and higher tides, and below the land as saltwater keeps infiltrating the groundwater.

In a study published last year, Tully and her colleagues showed how visible salt patches on land almost doubled from 2011 to 2017 and about 20,000 farmable acres were transformed into marsh.

KATE TULLY: So, that's pretty staggering, especially because the time period was small.

And so we're kind of this test bed.

So we don't have a lot of time.

And people are looking to this region for solutions, right,because we're kind of -- we might be a couple years, 10 years ahead of what folks are going to see in other parts of the world.

WILLIAM BRANGHAM: Perhaps the starkest example of what salt can do to this landscape is right here.

This is what they call a ghost forest, and 20 years ago, all those white stumps that you see behind me were living green pine trees.

As salty water crept into this forest, it poisoned all those trees, like it does to most crops.

It's the exact fate farmer Wendell Meekins is trying to avoid in his nearby fields.

WENDELL MEEKINS, Dorchester County, Maryland, Farmer: The soil structure has gone from a farmable, tillable soil, and it's changing into a marshland.

All of this now has become what you would essentially look at as a river bottom.

WILLIAM BRANGHAM: A massive tidal surge of saltwater last year killed 65 acres of corn that he'd planted on these fields.

WENDELL MEEKINS: I mean, it just devastated this whole crop.

It was a 100 percent loss.

WILLIAM BRANGHAM: Meekins says managing salty water in this low-lying region has always been a challenge.

The fields here are flanked by ditches designed to keep the tidal flows away from his crops.

This year, he built up more protection.

WENDELL MEEKINS: Well, this is a berm that we've tried to put up.

I'd say this is about three feet higher than your ditch bank here, trying to keep some of the tidal surge at bay.

WILLIAM BRANGHAM: But he acknowledges it's all just a Band-Aid.

WENDELL MEEKINS: If we see the water changes that I have seen in 2023 in 2024 and 2025, we're in big, big trouble here.

WILLIAM BRANGHAM: So you think its crystal clear that farming cannot continue over the long haul here?

WENDELL MEEKINS: Not here, nope, 100 percent over.

KATE TULLY: How has this salt patch, like, extended in your memory, like over time?

WILLIAM BRANGHAM: Researcher Kate Tully says there are some crops that might survive in saltier soil, like sorghum or even quinoa.

KATE TULLY: Some farmers will start planting sorghum or another crop that might be more salt-tolerant and have less inputs, but it's going to have a lower return on it.

I mean, it's a lower profit.

WILLIAM BRANGHAM: You don't get as much money out of that.

KATE TULLY: That you -- as you do out of corn.

But I will say that, in most cases, some of these farms where you see that salt damage, it's a little too late to really sort of remediate that property.

WILLIAM BRANGHAM: Fifth-generation farmer Kevin Anderson says he's desperate for some clear guidance.

KEVIN ANDERSON: We just don't know what to do.

There's not a program.

There's not a strategy.

We're just kind of left out here for each individual farmer to see what works and what doesn't work with our own time and our own money.

WILLIAM BRANGHAM: He too has considered building a barrier against the tide, but isn't sure if it's worth the investment.

KEVIN ANDERSON: We're looking for someone to help us draw a line in the sand and say, this elevation is where you need to protect.

And from this elevation below, in 20 years, it's not going to be here.

WILLIAM BRANGHAM: To help farmers get a handle on how their lands are changing, the University of Delaware's Jarrod Miller uses drones to photograph how crops are growing, and matches those with measurements of salinity in the soil.

JARROD MILLER, University of Delaware: A lot of times, with agricultural research, we might have yield at the end of the season, but what drones have provided us with is measurements of plant growth or correlations to plant growth throughout the season.

It's been another piece of information that's really helped us line up and make sure that our soil measurements we're taking match what we expected.

WILLIAM BRANGHAM: Miller says data like this can help farmers make tricky economic calculations.

JARROD MILLER: It's a tight margin on that grain.

So, every time you lose an acre, you lose yield.

And there's only so many acres left on Delmarva to make any money off of.

So, every time we lose this bit, you might be cutting into someone's bottom line or their survival.

WILLIAM BRANGHAM: But with sea level expected to rise nearly three feet in this region by 2100, a lot of current farmland will likely turn to salt marsh.

KATE TULLY: On the positive side, if we thoughtfully manage these agricultural fields as they are starting to be intruded, we could allow that to sort of transition into marsh, and that would store a lot of carbon underground.

And it actually can serve as a buffer for storm surge.

WILLIAM BRANGHAM: But for farmers like Wendell Meekins, finding ways to save agricultural land while he can is his top priority.

WENDELL MEEKINS: We need to protect what we have here now and find a use for it.

It's -- it really takes some thinking to do something the right way for future generations.

WILLIAM BRANGHAM: A future that will include higher sea levels in a region with more than 2,500 miles of coastline.

For the PBS "News Hour," I'm William Brangham on the Eastern Shore of Maryland.