Decades after the proliferation of nonnative grasses, an unexpected variant is once again changing the ecosystem
Shifting sands: Beach grass in Oregon (pictured) and Washington ain’t what it used to be. Photo: OSU
By Lauren Ellenbecker. May 2, 2024. Over a century ago, settlers irreversibly altered the Pacific Coast’s natural shape with the introduction of two nonnative grass species.
Now, a new hybrid is making headway, presenting challenges for dune restoration.
“In the U.S. Pacific Northwest, two invasive, dune-building beachgrasses, Ammophila arenaria (European beachgrass) and A. breviligulata (American beachgrass), have hybridized and formed a new beachgrass taxa (Ammophila arenaria×A. breviligulata), but little is known about its distribution, spread and ecological consequences,” according to a study published last month in the journal Ecosphere.
The study was conducted by researchers at Oregon State University, who led a large-scale survey along Washington and Oregon’s coastline, finding nearly 300 individual hybrids of European and American beach grass.
Sally Hacker. Photo: OSU
While affirming the hybrid’s far reach, researchers also found these grasses were within and near conservation habitats designated for the western snowy plover and streaked horned lark, both listed under the Endangered Species Act.
The findings built off a 2021 discovery of only a dozen hybrid sites along the coast. The hybrid was first observed in 2012.
“It creeped up on us. You would never have thought of hybridization being a likelihood,” says Sally Hacker, an OSU coastal ecologist and one of the study’s co-authors. “It all happened in this intentional yet unlikely way.”
European beach grass has thin blades that reach toward the sky, creating tall and narrow dunes.
Its rhizomes can shoot upward, allowing the hardy clumps to keep pace with towering sand.
American beach grass slightly differs, growing fewer thick stalks to form short, wide dunes.
Where the two overlap, hybrids may appear and outshine the parent species by being both tall and wide, says Hacker.
Of further concern, hybrid beach grass could crossbreed with European and American beach grasses, allowing genes to flow between the invasive species—fueling their dominance along the coast, competing with native species and making beaches narrower.
“They’re everywhere,” says Hacker. “They’re going to be exponential in abundance.”
Pre-invasion coast
Pacific Northwest shorelines were originally only sparsely dotted with vegetation.
Sand moved freely along expansive, low-lying plains similarly to a river, according to Celeste Lebo, a regional habitat restoration biologist with the U.S. Fish and Wildlife Service. The landscape was constantly transforming under wind and tidal influences, untethered by masses of grass.
Native vegetation shaped lower dunes that melted and swelled under the wind’s push and pull. These plants became accustomed to seasons of being completely buried, only to flower again and reproduce.
Bundles of pink and yellow sandverbena, beach pea and seashore lupine accented white expanses. American searocket, beach strawberry and beach morning glory, too, appeared season after season
Distribution and relative abundance of Ammophila arenaria (red) and Ammophila breviligulata (blue) on the Pacific Coast. Map: Askerooth, R., R. Mostow, P. Ruggiero, F. Barreto, and S. Hacker. 2024. “A Novel Hybrid Beachgrass Is Invading U.S. Pacific Northwest Dunes with Potential Ecosystem Consequences.” https://doi.org/10.5061/dryad.x0k6djhr4
But the Pacific Coast’s native openness wasn’t conducive to the modern human lifestyle.
Fine particles of sand would slowly accumulate along a home’s window frames, on the porch and between cracks.
Without a barrier to break the wind, sand could engulf an entire house, sometimes piling up to its roof and cracking weak points under its weight, according to Meg Reed, an Oregon coastal policy specialist with the Oregon Department of Land Conservation and Development.
Beginning in the early 20th century, settlers planted European beachgrass near Florence to serve as a windbreak, a practice the U.S. Forest Service oversaw years later.
Beach grasses: Blue dot indicates Ammophila breviligulata; red dots indicate Ammophila arenaria. Photo: Sally Hacker
Shortly after, American beach grass, native to the East Coast and Great Lakes, debuted along the Clatsop Peninsula near the mouth of the Columbia River.
By the 1950s, nonnative beach grasses had spread from Mexico to Canada.
“When this change happened, with this planting of nonnative grasses, it just totally changed the landscape and made it difficult for native species to compete,” says Reed.
Managing, not eradicating
The beach grasses’ invasion of the Pacific Coast is permanent.
This year, the Washington Noxious Weed Control Board* classified European, American and hybrid beach grass as a “Class C” weed, a designation that reflects the species’ invasive nature without requiring control.
A listing, however, can help local organizations, governments and agencies acquire funding for beach grass management.
Field work: Dune restoration projects are in play up and down the coast. Photo: Lauren Ellenbecker
Lebo says mending dunes is a relatively new area of focus, as opposed to rehabilitating estuaries and coastal prairies.
Pacific Coast dune restoration thus presents novel challenges—this is an area of focus that remains largely unexplored—as environmental managers attempt to keep pace with an endlessly morphing landscape.
Restorative efforts by public and private entities are nevertheless scattered across coastal communities in Washington and Oregon. These include a large dunes restoration undertaking at the Siuslaw National Forest on Oregon’s central coast by a coalition of stakeholders including federal, tribal, state and county agencies, watershed councils, recreation groups and environmental groups.
Beach grass management can involve scraping away invasive grasses with mechanical equipment, spraying them with herbicide or prescribing burns.
Practices can be more intensive, involving digging a trench the width of a bulldozer, tearing beach grass off the top, burying it and smoothing the surface.
Management efforts can be indiscriminate, leaving a lasting impact on all plants within treated areas, regardless of native origin. Invertebrates residing in wet sand can be smothered when freshly dug material is placed on top of them.
Even further, studies illustrate that snowy plovers can require a 100-foot radius surrounding their nest to feel comfortable. The tiny birds collect shells, driftwood and various beach scraps to make their home, a process easily disrupted by human disturbances.
Dune conservation effort “way behind”
Habitat experts such as Lebo hope to centralize coastal dune restoration within one concept.
“How do we restore natural dune processes in ways that are self-sustaining?” she says.
The Oregon Coastal Dune Partnership, which Lebo helps spearhead, aims to restore the Oregon Coast’s native dunes and the species that depend on them.
Celeste Lebo. Photo: Institute for Applied Ecology
Partnership members have returned to documented sites in the dunes where native plant communities or rare plant species were known to occur. She says they either can’t find them, or find the habitat degraded by invasive beach grasses, leading them to wonder whether remnant patches of native plants can persist.
“At this point, we’re recognizing that we’re way behind in conserving species that are dependent on natural dune ecosystems,” says Lebo.
Can’t be undone
Nearly 45% of Oregon and Washington’s coastline is composed of beaches and dunes and, among them, a string of small communities.
Foredunes—low hills formed parallel to the ocean edge consisting of sand and driftwood and usually capped by European beach grass—are common along the coast.
Modern life on the coast depends on these sandy walls, which spare residents from the torment of sand dirtying streets or damaging homes during winter storms.
Environmental managers seek to balance tradeoffs that foredunes present, including restoring dunes to support biodiversity versus protecting coastal development by prioritizing beach grass, says Rhiannon Bezore, a coastal shores specialist with the Oregon Department of Land Conservation and Development.
With help from an OSU doctoral student, the State of Oregon is readying an update to its coastal guidebook, a task last done in 1989. In doing so, it hopes to provide coastal residents with best practices for tending to the dunes in their backyard, including what types of vegetation they can plant.
The Oregon Coastal Dune Partnership and other groups will continue to apply for research grants and explore uncharted territory.
“There’s a lot we just don’t know,” says Lebo, adding this is what makes this realm of study so important.
