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How three unassuming plants link Vermont to its glacial past

At Alburgh Dunes State Park, a split rail fence surrounds an unassuming site. Green grass covers a pile of sand, framed by trees a few meters back. But as with many things in nature, this apparently harmonious scene is in fact a battlefield, stretching back thousands of years. And the continued survival of that grass is no small feat.

In Vermont, there are several plants directly tied to the Champlain Sea. These species are called maritime disjuncts, owing to their separation from their coastal ancestors thousands of years ago, and they exist in small populations today in the beaches around Lake Champlain. Highly adapted to this environment, these unique species are some of the few living remnants of that era.

The grass on Alburgh’s dunes is Champlain beachgrass, a subspecies of American beachgrass. While American beachgrass is commonly found on the Atlantic and Great Lakes coasts, Champlain beachgrass is much rarer. In Vermont, there are only two known locations: the Alburgh Dunes and North Beach in Burlington.

A group of beachgrass pockets a dune in Alburgh.
Kate Kruesi
/
Courtesy
At Alburgh Dunes state park, a living relic lies along the beach.

Beachgrass is a rhizomatous grass, meaning most of its biomass is underground in the form of large, thick horizontal stems called rhizomes. Rhizomes are the reason dune grass species like beachgrass are so important for erosion control: they literally hold the soil in place.

Champlain beachgrass blooms earlier than American beachgrass and is genetically distinct, hence its classification as a subspecies, said Dave Barrington, professor emeritus of plant biology at the University of Vermont.

The population at Alburgh was first documented in 1878 by the famed American botanist Cyrus Pringle. Before the area became a state park in 1996, some dunes were bulldozed for sand to replenish the beach, destroying critical habitat. Nevertheless, the Alburgh population survived.

Beach heather is another maritime disjunct. Like beachgrass, it’s rhizomatous and thrives in sandy environments. It’s also rare: there were seven known populations in Vermont, but scientists haven’t seen beach heather at three of the sites for decades.

Beach heather is a mat-forming shrub, meaning it expands outward through cloning, in some cases creating large concentric circles of a single clone. Beach heather has yellow flowers that bloom between May and July. Vermont’s population is not different enough to be a subspecies like Champlain beachgrass.

The last of the three maritime disjuncts is beach pea, a legume. Common to the New England coast, it produces lavender flowers. Vermont’s beach peas are the same variety as their Atlantic coast counterparts.

Kate Kruesi, a lifelong gardener who volunteers for the state, recalled the first time she saw a population of beach pea after moving to the Burlington area.

“It was a really moving experience, first seeing beach pea that was genetically connected to beach pea that was here like 8,000 years ago,” Kruesi said. “I felt like I was touching the deep past when I was first encountering those populations.”

A vine-like plant with lavender flowers sits on leaf litter.
Kate Kruesi
/
Courtesy
Beach pea is recognizable by its lavender flowers.

Lovers of disruption

The three maritime disjuncts all share one important trait: they require not just sand but shifting sands to thrive.

“Some of the rarer plants in the state are what we call disturbance colonizers. They thrive on pioneering and open habitats. And the only reason they’re going to remain in our flora is if that kind of open habitat is sustained,” said Barrington.

Like beachgrass, beach heather thrives in environments where disturbances push out competitors. Barrington, the plant biology professor, described one population of beach heather in Colchester that was inadvertently maintained by ATVs.

In the past, ATVs were allowed to roam freely on a sandy area populated by beach heather, as evidenced by tire tracks visible on the sand, Barrington said. When the state put up a fence to protect the habitat, it created a cascading effect.

“What happened was that instead of open sand and extensive disturbances, things stabilized and regular weeds started to move in, and then even trees. So there’s a rapid succession of vegetation,” Barrington said. “The open sand was virtually going out of existence, and the beach heather declined, right alongside that stabilization.”

Counterintuitively, the three maritime disjuncts require a disruptive environment to outcompete other species.

Beach pea’s iconic lavender flowers can sometimes be seen at the base of erosional bluffs, which are sandy, unstable lakeshore cliffs. This is because, as state botanist Grace Glynn explained, the plant thrives at the top of the bluff where other species can’t survive. When it inevitably sloughs off, it slides down to the bottom. This puts it at greater risk of flooding, though the species’ seeds can survive even in salt water for several years.

The challenge of preservation

Preserving species that crave disruption is a complicated task. Sometimes interventions can have an unintended effect, as in the case of protecting beach heather from ATVs, or even in using the wrong kind of fencing.

Until last year, the beachgrass population at Alburgh was protected by a snow fence, a series of vertical wooden slats which act as windbreaks, preventing sand from blowing through. But beachgrass, whose genus name Ammophila literally translates to “sand-lover,” needs shifting sands to survive.

Last year, the Vermont Department of Fish and Wildlife, partnering with the Native Plant Trust, replaced 375 feet of fencing to allow sand to flow freely onto the dunes.

A snow fence consisting of grey wooden pickets tied together with wire blocks the Alburgh Sand Dune site
Vermont Fish and Wildlife
The old sand fence in Alburgh prevented sand from moving freely onto the dunes, which beachgrass thrives in.
A split-rail fence with an open bottom allows wind to carry sand onto the Alburgh Dune site.
Braden DeForge
/
Courtesy
The newly installed split-rail fence has an open bottom, allowing sand through.

Anecdotally, Glynn said, the beachgrass seems to be doing better since the new fencing was installed.

“That process of disturbance, that process of sand deposition, is keeping woody plants out,” Glynn said. “Woody plants, when they come in and stabilize a dune, they out-compete these dune species like beachgrass.”

Extreme flooding is also a concern for the survival of the maritime disjuncts. While July’s flooding didn’t raise Lake Champlain enough to damage them, Hurricane Irene devastated two dunes on Alburgh back in 2011.

Fish and Wildlife and Native Plant Trust transplanted a small amount of beachgrass rhizome from Alburgh dunes to two nearby dune sites that lost their population following Hurricane Irene. More than 70% of the transplanted plants were alive and growing as of last year, Glynn said.

The disjuncts are also threatened by invasive species. Weeds like knapweed and non-native plants like beach rose need to be pulled before they crowd out a habitat. American beachgrass, sometimes planted to stabilize dunes, outcompetes its Champlain sibling. Generally, management takes the form of opportunistically pulling while conducting surveys, Glynn said. In areas where woody plants threaten to shade out the maritime disjuncts, they’ll sometimes engage in select cutting with saws.

Kruesi took up management of a population of beach heather three years ago, weeding and clearing the site four to five times a year, she said, to maintain the plant without mowing it multiple times a year. She pulls hawkeed in the spring, crabgrass in the summer, and leaf litter in the fall.

A small collection of dark green leaves clusters in a sandy lot, surrounded by grass.
Kate Kruesi
/
Courtesy
The beach heather population managed by Kate Kruesi. Her son's legs are in the background.

For larger projects, the state partners with organizations like the Native Plant Trust and the Cotyledon Fund to hire contractors for large-scale digging and pulling of invasive species.

In some cases, the environments inhabited by maritime disjuncts are undesirable to people. Erosional bluffs are potentially dangerous to nearby structures, but attempting to ward off erosion with riprap (layers of stones placed to protect a shoreline from erosion) prevents plants like beach pea from growing there.

'This is very much tied up in values'

While rare, the maritime disjuncts are anything but fragile, relying on precarious environments few plants can survive in; nor are they simply exhibits: their ability to bind sand dunes is a necessary part of a healthy ecosystem.

But although they’ve survived up to now, Glynn said, they’re reliant on very specific environments that can be unattractive to people.

“One could say, ‘Oh well, you should just let things play out on their own,’ but we’ve interfered quite a lot with processes. We have no examples of sand dunes that are undisturbed in this state,” Glynn said. “I think that because we are so intertwined with these places and they’ve undergone so much human disturbance that we do have an obligation to try to restore them.”

Kruesi sees the value of these species in part in their resilience. The beach heather population she manages exists only because the former airstrip on which it lives, now mowed and maintained as a park, is close to its natural backdune habitat. If it required cutting down trees and removing leaves en masse to save a small population, it wouldn’t be worth it, she said.

“I was volunteering to manage a population that only needed a little bit of effort to be in a site that already provided most of the disturbance and sunlight needed for that plant population to grow,” Kruesi said. “Why not protect that?”

Beyond that, Kruesi said, there’s value in knowing that something so ancient and resilient is still around. When people walk by a population like the Alburgh Dunes beachgrass, they should know that grass they see is a story thousands of years in the making.

“I think we need to tell the stories because people then own the story of the Champlain Sea or own ‘This is a special grass. This is a special sense of place,’” Kruesi said. “We want people to own this information, to connect more with nature around them.”

Noah Villamarin-Cutter assisted with digital presentation of this story.

Have questions, comments or tips? Send us a message.

Corey Dockser is Vermont Public’s first data journalist, a role combining programming and journalism to produce stories that would otherwise go unheard. His work ranges from complex interactive visualizations to simple web scraping and data cleaning. Corey graduated from Northeastern University in 2022 with a BS in data science and journalism. He previously worked at The Buffalo News in Buffalo, New York as a Dow Jones News Fund Data Journalism intern, and at The Boston Globe.