Sea level rise: Saltwater intrusion laying waste to Delmarva farms

Jeremy Cox

Bay Journal News Service

Bob Fitzgerald and his ancestors have farmed the same land on Maryland’s Eastern Shore off and on since 1666. He will be the last.

Dubbed “Waller’s Adventure,” the 160-acre farm has begun sinking at an alarming rate. What started as a “little wet spot” has swollen in just the last few years into a bowl-shaped, 2-acre void, Fitzgerald said.

“You can see where it’s dead soil,” he said, pointing to a bare swath of sand in the middle of the depression.

“This is how you lose it,” the 79-year-old added with rising concern in his voice. “This is how it starts.”

The problem is a common countertop substance that doubles as an ancient scourge to farmers: salt.

Saltwater, pushed onto the surface and into the groundwater of some Eastern Shore farmland by rising the sea level, is making crop production increasingly difficult. And saltwater intrusion has already started to force some Shore farmers off their land, according to emerging research led by the University of Maryland.

“It’s happening now,” said agro-ecologist Kate Tully, the team’s leader. “We often talk about sea level rise and climate change as this thing that’s going to happen in the future. And it’s already happening. We’re at the point we’re already losing farm fields.”

"This is how it starts.” Somerset County farmer Bob Fitzgerald looks over what started as a “little wet spot” that has swollen in just the last few years into a bowl-shaped, 2-acre void.

In rural Somerset County, home to Fitzgerald’s corn and soybean operation, the researchers used land-cover-sensing software to determine that farmland has been converting to salt marsh at a rate of about 100 acres per year since 2009. That adds up to 860 acres lost, the equivalent of four average-size farms.

“Now we have to think about how much we’re going to lose in the next five years,” Tully said, and how to manage the farms where salt is beginning to intrude.

No one has mapped how much land across the low-lying Eastern Shore has been affected by saltwater intrusion. Creating such a map is part of Tully’s five-year, $1.3 million research project. The effort is now in its second year.

The researchers’ work, funded largely by the U.S. Department of Agriculture, is primarily aimed at providing answers for the farming sector — the Shore’s biggest industry. But it also could carry implications for the multi-state and federal restoration of the Chesapeake Bay, Tully said.

That’s because salt, by a quirk of chemistry, has a knack for dislodging nutrients in farm soil. Instead of remaining chemically bound to the soil, nitrogen and phosphorus break free.

From there, rainfall can whisk those nutrients into one waterway, then another and eventually into the bay, where they fuel algae blooms and trigger a cascade of harmful ecological events.

There are lots of nutrients in the soil

And there are lots of nutrients in Eastern Shore soil. Portions of the Shore’s farmland are saturated with nutrients, particularly with phosphorus, from decades of fertilization at levels that exceed the plants’ ability to use it.

According to the first scientific paper to be published from the team’s research, “these agricultural legacies will likely be unlocked as saltwater intrudes on farmlands and have devastating consequences for downstream ecosystems.”

Somerset County farmer Bob Fitzgerald points to a bowl-shaped, 2-acre void created by saltwater intrusion.

The Chesapeake Bay Program computer model estimates that guide the bay cleanup may need to be revised to account for saltwater impacts in some locations, said Keryn Gedan, a coastal ecologist at George Washington University who launched the study with Tully.

“We haven’t gotten to a point where those numbers can be put into the bay model, but we think they (the model’s architects) will be interested,” she said.

The pair said they decided to conduct their study in the bay region because it is one of the world’s hot spots for sea level rise.

Water levels off Maryland’s shores are rising faster than the global average. Scientists attribute the accelerated regional trend to two factors working in concert: a weakening Gulf Stream coupled with land levels sinking in the wake of their bulging during the last Ice Age.

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As a result, experts predict that Maryland’s “relative” sea level rise will reach 3.7 feet by 2100; the global average is projected to be 2.7 feet.

On the Eastern Shore, saltwater intrusion has been one of the forerunners of climate change, Tully said.

“It kind of moves ahead of sea level rise. When you get to the point you’re having chronic flooding on your field, you have this very visible water line. Saltwater intrusion will actually push ahead of that line,” she said.

Larry Fykes has been assisting farmers as part of the Somerset Soil Conservation District for 35 years, most of it as the agency’s district manager.

Salty soil has been a growing headache in coastal areas for years, but it began accelerating after Hurricane Sandy flooded much of the county in 2012, he said.

Brackish water stands in the moatlike ditches surrounding a home west of Princess Anne.

Exceptionally high tides — which climate scientists refer to as “sunny day flooding” — used to strike once every six months. But since Sandy, they seem to come every month. And he doesn’t know why.

“Something’s going on,” Fykes said. “These tides come up (onto a farm), and the next year they come up another 20 feet. And the next year they come up another 20 feet.”

Once the salt has worked its way into the soil, he added, “it’s there forever.”

Forces conspiring to taint the farms

In fact, a variety of forces are conspiring to taint the Shore’s farms with salt, Tully said.

Storm surges pile tidewater onto the land with increasing regularity. Irrigation pumps can thin underground freshwater reserves, drawing in the surrounding saltwater to take its place.

Meanwhile, ditches and canals can introduce salty water from tidal creeks far into agricultural fields.

The soil can become saltier than the ocean itself, Tully said. Once the water evaporates or runs off, it leaves behind dense salt deposits.

The ocean’s salinity averages about 35 parts per thousand. But in a salt marsh, where the water routinely ebbs and flows, plants need to tolerate salt concentrations that can spike as high as 60 parts per thousand.

Some farms in the lowest-lying parts of the Shore are slowly turning into salt marsh, mainly in coastal Somerset and Dorchester counties, Tully said. But it’s spreading.

Behind the wheel of his red Ford F-150 pickup truck, Fitzgerald pointed out one abandoned field after another in the western portion of Somerset.

“All this was farmed two years ago,” he said, gesturing toward one expanse of yellow, stalky phragmites and salt marsh hay. “He just got tired of fighting it.”

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The problem is shared throughout the Delmarva Peninsula, the 170-mile-long elbow jutting into the Atlantic Ocean between Philadelphia and Virginia Beach. Many of its farmers aren’t giving up easily, installing tide gates on drainage pipes to keep saltwater at bay and switching to more salt-tolerant crops.

A farm typically doesn’t falter overnight, Fitzgerald said. Soybeans can withstand salt concentrations up to about 3 parts per thousand; corn, 1 part per thousand. Encroaching salt first reduces a field’s yield — the amount of crops it produces. Over time, yields dip too low for it to remain financially viable.

“It becomes what we call marginal land,” said Jarrod Miller, a soil expert with the University of Delaware. “It’s not the most productive. So how do you keep that in production?”

Most of Somerset County’s $219 million agriculture industry revolves around poultry production: raising chickens or planting corn and soybeans to feed the birds. Nearly 50,000 acres out of the county’s total 207,000 acres of land are given over to farming.

But, for a variety of reasons, farmers there have given up tilling on at least 4,000 acres of their holdings that have been put into land preservation programs in exchange for tax benefits.

Miller is working with Tully and Gedan on another piece of their study. Last year, the researchers and their interns planted test plots, known as “strip trials,” on several farms in Somerset and Dorchester counties where saltwater intrusion has become a problem.

Soybeans, sorghum and ... sand? Saltwater intrusion is turning some Eastern Shore farms into barren fields. Researchers are working to help farmers cope with test plots like this.

Their goal is to determine over five years which crops perform the best and in what seasons they thrive the most.

With its low tolerance to salt, corn was a non-starter for Miller. That left him with barley, soybeans and sorghum, a grass used for fodder. The growing season soon turned into a monsoon, forcing him to replant twice in some areas.

“It’s the reason you do five-year projects — because one year is never good enough,” he said.

For their part, Tully and Gedan chose to lean in to the salty regime, growing plugs of salt marsh hay and switchgrass. While not exactly staples of the American food system, the salt marsh hay could be used for restoration plantings, and switchgrass could be marketed to biofuel producers, Gedan said.