Special Series
This is Part 1 of a three-part series “Salt of the Earth” that examines the creeping threat of saltwater on the health of Delaware.
Why Should Delaware Care?
Climate change and sea level rise aren’t going to make the First State fall into the ocean overnight. But the slow creep of salty tides is showing that change is happening – and in the cases of Delaware’s rarest plants and habitats, that change may be happening far too quickly for natural systems to keep pace, risking unrecoverable losses of the state’s natural heritage.
The first time botanist Bill McAvoy visited the Cherry Walk Fen, a very specific, rare wetland about a mile’s walk into the woods of Angola Neck, he said it was a true “wow” moment.
More than two dozen rare plants, many that he never would have expected to find here, were thriving in a freshwater habitat that couldn’t even exist much farther north.
“Lo and behold, it was probably the best example known out of its entire distribution,” McAvoy said as he recollected his first visit to the site, alongside other botanists and wetland ecologists, in 1993.
After a short walk through state-owned coastal forest on the edge of Rehoboth Bay, he would come to find rose begonia, a pink wetland flower that provides pollen for native bees. There was the colorful Calopogon tuberosus, a purple-colored orchid native to the East Coast. Rare sedges and herbs like the fringed yellow-eyed grass and horsetail spikerush that were known to exist locally at only one or two sites were also found here.
Over the years, McAvoy would walk along Cherry Walk Creek to reach that rare habitat at least a dozen times. And as each year passed, the incoming tides creeped ever closer.
By 2022, it was clear to McAvoy that saltwater had begun to overwhelm the mostly freshwater system, a process that had likely started even earlier than that.
“With sea level rise increasing every year, the salinity levels are also increasing now to the point where the freshwater is not enough to push it back, and those sea-level fens are now salt marshes,” he said. “And all the rare plants they supported are locally extinct, or extirpated, from Delaware.”
Each year, sea level measured at Lewes has risen by about 3.77 millimeters, according to the National Oceanic and Atmospheric Administration. But from 2004 to 2023, that rate has nearly doubled, to about 7 millimeters per year. Future sea level rise projections, which vary depending on whether anything is done to curb human impacts on the climate, show the area could see at least another foot or more of sea level rise by mid-century.
When McAvoy last visited the Cherry Walk site, most of the rare plants that wowed him decades ago were long gone. Invasive phragmites have sprouted in a small, bleak army of tan reeds along the edges, indicating disturbance and a loss of native plants.
“We’re losing a habitat and a plant community that I think was probably more widespread in the state than it was when we first started to find these communities,” McAvoy said. “Part of our natural heritage is gone.”
What is saltwater intrusion?
Delaware environmental scientists often note that in the coastal First State, nearly anywhere you stand, you’re within 1 mile of a waterway.
The further south and east you go, the more likely it is that the water encountered will be salty. That’s great for living the “salt life” that some lower Delaware fans love. But, especially with climate change leading to higher tides and stronger storms, the eastward movement of saltwater, whether due to natural or man-made forces, can threaten drinking water supplies, vulnerable infrastructure and soil health.
The Delaware Geological Survey scientists say those scenarios can be split into two main types of salt risk: Salinization and saltwater intrusion.
Salinization occurs when saltwater washes onto the land or freshwater areas, like during storms that push higher tides into coastal marshes.
Saltwater intrusion occurs when saltwater from sources like the Delaware Bay get pulled inland through underground aquifer systems.
Think of an aquifer like an underground river. If that river connects to the Delaware Bay, imagine there’s a big mixing zone, or wedge, where the two water sources meet (the wedge is created since saltwater is heavier than freshwater). That “salt wedge” can shift back and forth naturally: A heavy rain might mean more freshwater enters the system, so the wedge would move closer to the bay. Drought conditions coupled with irrigation wells could pull that freshwater more inland.
Coastal beacons of change
As these rare plants and places disappear, so too does the biodiversity that can be found across Delaware. “Ghost forests” are popping up along the edges of Delaware Bay and the state’s three smaller inland bays to the west of its beach towns, indicating an intrusion of salt that’s killing off the plants that are holding together habitats and shorelines.
“The trees are those canaries that tell us the saltwater is coming,” said Meghan Noe Fellows, director of estuary science and restoration at the nonprofit Delaware Center for the Inland Bays, of the clusters of gray, leafless trees that died due to soaking up too much salt along the edges of the inland bays and Delaware Bay. “The salt’s coming too fast.”
For years, environmental advocates have estimated that Delaware loses about 1 acre of wetlands every year for a variety of reasons, from development to erosion. At the same time, the state notes that wetlands comprise about 25% of Delaware’s land mass. And nearly half of the state’s wetlands — over 140,000 acres — are found in Sussex County.
That’s potentially a lot of southern Delaware at stake as climate change drives sea levels higher and produces the perfect conditions for more extreme weather events.
As a coastal state, these ecosystems not only provide valuable habitat to those rare plants and animals, but also act as sponges during storm events. Marshes are meant to be wet, and can absorb floodwaters while development or infrastructure built farther inland stays dry — or at least drier than it would if there was nothing in between to hold those floodwaters.
“Sea level has gone up and down over the millenia,” said Noe Fellows, but the recent acceleration is shifting the outcome. “The ecosystems can’t keep up with the pace of the change.”
In the state’s most recent wetlands report spanning 2007-2017, the state found that about 919 acres of wetlands (about the size of Brandywine State Park) were significantly changed by saltwater intrusion or rising sea levels. That means some 15% of the marsh type changes seen during that period were due to systems becoming fully tidal – meaning they also became predominantly salty systems.
Overall, the state lost a total of just over 3,000 acres of wetlands during that decade. About 2,000 of those acres disappeared in Sussex County — with 98% of those losses being nontidal wetlands, which are typically freshwater systems, according to the report.
Relying on data that’s nearly a decade old also makes it challenging to know how far the problem has spread. State officials said the next updated wetlands report is slated for 2027.
The Delaware Department of Natural Resources and Environmental Control also recently released a new marsh migration tool along with a detailed study that examined whether marshes will be able to migrate inland. For example, if developments or impervious surfaces are built along the shoreline already, even a healthy marsh wouldn’t be able to slowly adapt and move inland as the tides rise because there’s nowhere for it to go.
And if the tides rise too fast, some marshes cannot keep up. Yet, some 20,000-plus acres of marsh that could be affected by rising sea levels appears to be in good shape to migrate, based on that model.
“Wetlands need to migrate,” said Alison Rogerson, an environmental scientist with the state’s wetlands program. “That’s a tough pill to swallow if that’s your [farm] land or your yard.”
An uphill battle
The fight against rising salty tides from the east would be easier if more freshwater could flow from western headwaters farther inland.
Many of Delaware’s mill towns that were formed around waterways a little farther off the coast, like Millsboro, have dams because they were once active mill towns. The mills are no more, but the dams remain – impeding the freshwater from flowing and balancing out the salinity.
That means native freshwater species, like the purple-leafed Lobelia elongata (aka “longleaf lobelia”) that once grew in plentiful numbers along the river’s banks, are now nearly impossible to find.
Or at least they would be if McAvoy hadn’t planted some along the freshwater pond behind the Millsboro dam.
“That only occurred in the inland bays in these fresh-to-brackish tidal marshes,” he said. “Again, they’re all gone.”
The persistence of longleaf lobelia on the other side of the Millsboro dam is somewhat artificial, he says, but it’s one small thing he was able to do to offset the loss of biodiversity that he’s seen escalate over the years.
“Whenever you start losing biodiversity, there’s so many other things that affect it,” he said. “How do we know there wasn’t a moth or butterfly that was associated with Lobelia elongata? Perhaps there was a bird that fed on that moth or butterfly or insect, so now that bird is affected. It goes right down the line.”
That’s been the same question that researchers like Christopher “Kitt” Heckscher of Delaware State University have been asking as they study other rare habitat-dependent species like the Bethany Beach firefly. This state-rare species also depends on another rare type of wetland that lacks many regulatory protections, at least one of which was literally paved over to make way for multi-million-dollar beach homes.
But there may be other species that depend on these specific habitats for survival that might be lost before they’re even discovered due to these habitat losses, manmade or otherwise.
“By losing all these freshwater habitats and freshwater species, it’s an indicator that there’s something wrong with our environment,” McAvoy said. “There’s something wrong there, and it’s becoming dysfunctional.”
Fighting changing tides
Sadly for the Cherry Walk Fen that McAvoy and others monitored for years as a beacon to the beauty of Delaware’s native flora and fauna, the tides were always going to come.
But it doesn’t have to be that way for all of these rare habitats, or tens of thousands of marsh acres across the state that could still migrate inland for survival. Identifying where these marshes can migrate, and who owns those lands, can set the framework for future pathways for them to migrate.
In Sussex County, saltwater can come in with the tides, but also reach freshwater systems or the land through underground aquifers and over the land during storm and flood events. It’s unclear how many freshwater habitats have been impacted by those occurrences in addition to sea-level rise, erosion and land use changes.
We’re losing our freshwater tidal system, not just in Delaware but throughout Delmarva … The problem is you can’t stop the tide.
DNREC BOTANIST BILL MCAVOY
Since Sussex also includes some of the lowest-lying areas of the nation’s lowest-lying state, that means there’s a slew of infrastructure in the way of those rising tides. It’s not unusual for county officials to shut down certain wastewater pump stations: in extreme events, the county’s engineer said some two dozen pump stations will be forced to shut down as saltwater overtops manholes on coastal roadways like River Road in Oak Orchard.
“Everything being flooded with freshwater is just exacerbated by having it be saltwater and then you have more people crowding around the coast … you’re exposing more people to those consequences,” Noe Fellows said. “If you know your house floods three times a year, what do you think is going to happen in 20 years or 50 years?
“We only have this narrow window to really put in place some tools that we know do help build resilience to those events. That sense of urgency isn’t here,” she added.
Dewey Beach was earmarked to receive some $1 million in federal funding to elevate its pump stations and address other infrastructure issues threatened by flooding, but was recently told by the U.S. Army Corps of Engineers that the project was on hold. No reasons or additional details were provided by the feds, Town Manager Bill Zolper said in late December.
Other coastal towns have considered floodgates on the canals to keep out the rising salty tides. The City of Lewes is even looking to move its wastewater treatment plant farther inland. But all of those projects are still years away.
Elsewhere in the county, the Delaware Geological Survey is working with the University of Delaware and the state to expand a well-monitoring network to watch for intruding saltwater. Saltwater could also affect agricultural operations, drinking water systems and other infrastructure built in harm’s way.
Meanwhile, the Delaware Center for the Inland Bays has been working to support coastal resiliency education and projects, particularly focusing in recent years on “green infrastructure” like living shorelines that can help stabilize areas suffering from erosion.
In the state’s capital, environmental organizations and others are working with state lawmakers like State Sen. Stephanie Hansen to introduce legislation in the upcoming session that addresses a lack of protections for nontidal freshwater wetlands, which largely are unprotected in the First State.
There may be small things organizations and private landowners can do to help these habitats thrive and migrate, but change is already occurring in what were once some of Delaware’s most diverse habitats.
“We’re losing our freshwater tidal system, not just in Delaware but throughout Delmarva, the Delaware estuary, throughout the Chesapeake Bay,” McAvoy said. “The problem is you can’t stop the tide.”
Transparency Notice
Maddy Lauria previously worked for the Delaware Center for the Inland Bays from 2020 to 2021. She is currently an independent journalist based in Dover.