There is something otherworldly about walking among the dunes on Oregon’s Coast. Walking from crest to crest of these rolling hills of sand feels akin to walking atop ocean waves. With each step the sand shifts underfoot, and you wonder if you just might comfortably fall into a deep crystalline sea.
Despite the strangeness of the sand dune landscape, dune ecosystems are common along Oregon’s Coastline (though not so much elsewhere). Formed following the last Ice Age by the erosion of the sedimentary rocks of Oregon’s coastal mountain range, Oregon’s dunes are sculpted and shaped by the seasonal influences of water and wind and the surrounding terrain. The result is a menagerie of dunes of varied shape, size, and expansiveness; some only a few hundred feet long, hedged in by headlands and other obstructions, while others stretch 10s-of-miles along the coast creating places like the Oregon Dunes National Recreation Area near Florence.
Given the ubiquitous and curious nature of dunes, it is no surprise that these large sandy masses, have been, and continue to be, influenced by people.
When European settlers flocked to the Oregon coast to establish communities in the late 1800s, they were immediately met with the challenge of living in a dynamic sand-swept environment. Rather than retreating, settlers managed the sand with what they considered the best weapon in their arsenal—European beachgrass. European beachgrass has been used extensively throughout the world for erosion control. Oregon is no exception. European beachgrass is now a defining character of Oregon’s Coastal Dunes, influencing not only dune formation but also dune ecology.
To better understand the story of dunes in the Pacific Northwest and the ecological significance of European beachgrass and another non-native grass, American beachgrass, I met up with Rebecca Mostow, dune ecologist, at Bob Straub State Park near Pacific City for an interview and hike.
The Hike
- Trailhead: Bob Straub State Park Trailhead
- Distance: approximately 1 mile
- Elevation: minimal
- Details: Plenty of paved parking at trailhead. No fee for parking. There is also bathroom with flushing toilets. There are signs and a map posted at the trailhead.
It was a cool spring day when I met up with Rebecca for our hike and interview. A marine layer of clouds hung low in the sky, threatening drizzle, but the weather remained mild and dry. After some brief introductions, Rebecca and I headed out along the back dune trail, or Marsh Trail, at Bob Straub Park with plans to eventually cut down to the beach.
Rich and Varied
As we made our way down an alley of shrubs and trees that line the entire back dune trail, Rebecca told me a bit about her background.
Rebecca’s undergraduate work was at Oberlin College, where she studied biology and plant systematics. She also got involved in a variety of different research projects, from an HIV vaccine research internship to an invasive snail survey. Her work continued to be rich and varied after graduation as well. She even spent some time on a tiny island with half a million sea birds and only two people for company.
However, it didn’t take long before Rebecca’s passion for plants drew her back. Even during her time watching sea birds, she admitted that she couldn’t help but notice the plants. “I made a baby flora of the island,” she remarked. She also worked for the BLM in Nevada, Carson City district, on plant conservation before ultimately ended up in graduate school at Oregon State University in Sally Hacker’s Lab.
Intentional Introductions
Even now, walking along the trail, Rebecca was drawn to the plants surrounding us. She admired the new shoots of the spruce trees that grew along the trail, impressed by their symmetry. “See the little pattern,” Rebecca exclaimed, “a Fibonacci spiral!”
As we continued along, however, another pattern became apparent, at least to Rebecca’s trained eyes. “All of the plants we are looking at were intentionally planted altogether,” she explained. European beachgrass was planted to help stabilize and build dunes, Shore Pine to provide native habitat, and invasive Scotch Broom as a nitrogen fixer.
“They were trying to engineer a coastal forest,” offered Rebecca, as an explanation.
Unstable
As mentioned previously, sand does not make the development of permanent human settlement easy, or in some cases possible. By vegetating the dynamic, shifting sand system that was once present in the area, it was converted into a more stable system. But at a cost.
Rebecca explained that many species rely on open sand for habitat. Species, like the Western Snowy Plover, require open sand for nesting. The Streaked Horned Lark is another species reliant on open sandy areas.
So, though sand stability is great for human habitation, it does result in a substantial loss in habitat for other species. Both the Western Snowy Plover and the Streaked Horned Lark are threatened species under the Endangered Species Act mainly due to habitat loss.
This Grass is not like the Others
I have never been very good at identifying grasses and grass-like plants. Beyond remembering the saying: “sedges have edges, reeds are round, and grasses bend their knees to the ground,” I have very little experience with grasses and couldn’t begin to tell species apart.
However, walking with Rebecca along the dune trail, literally lined with beach grass, it wasn’t long before I received an education.
“This is our native dune grass,” Rebecca chimed, pointing to a blue-twinged blade. She went on to explain that in addition to the color of the blade, there are many other characteristics that help distinguish American Dune grass, Leymus mollis, from the European beachgrass, Ammophila arenaria, that was brought in to build and stabilize dunes.
“The leaf blades are so much wider, and it has a more prominent midrib” than European beachgrass, said Rebecca.
The Pits
And then there are the pits. Okay, so they aren’t exactly “pits,” but if you look at the point where the leaf and stem meet, you can see something called a ligule, a thin translucent-white tissue growth found at this junction. “The ligule is the armpit hair of the grass,” said Rebecca partly in jest, as she bent back a leaf. But it is also one of the most surefire ways to differentiate between beach grasses. American dune grass has a ligule that is short and flat. European beachgrass has a ligule that is much longer. When you need to tell grasses apart, “Just look at the pit hair!” Rebecca exclaimed.
Growing Underground
After my ligule tutorial, I asked Rebecca why European settlers on the coast planted European beachgrass instead of our native Dune grass.
“It is our native grass,” responded Rebecca, “but it does not build dunes.” She pointed to a patch of American dune grass growing just along the trail. “It doesn’t grow very densely,” she explained. Each stem of American dune grass was spaced out a bit from the others. In contrast, European beachgrass is “super dense” allowing it to better capture sand and trap it in place.
“Look, these three stems are all the same plant,” Rebecca pointed out.
“It is amazing when you start to dig down,” explained Rebecca, referring the propagation of beach grasses. Even the native “dune” grass spreads via underground stems called rhizomes; they just send shoots up at longer intervals. It is the underground growth that truly makes European beachgrass a great dune builder.
Not Exactly Invasive
“Would it be considered invasive?” I asked at one point as we walked along, referring to the European beachgrass’ ability to spread and compete.
To be considered invasive, Rebecca explained, a species needs to meet certain criteria. “It has to do significant damage to the environment, human health, or the economy.” For example, “Scotch broom is a listed invasive weed,” said Rebecca. “It is causing a lot of economic damage.”
European beachgrass is not listed, because though it has some of the traits of an invasive species, including negative ecological impacts, it doesn’t meet the criteria. It benefits people in many ways, so it is difficult to say it is “causing harm,” even when some native species are being impacted.
Structure of a Dune
At this point, Rebecca and I hit a junction, and we agreed to cut down to the beach. But before we headed down, Rebecca explained a bit about the structure of dunes.
“We are on the crest of the foredune; the dune closest to the ocean,” said Rebecca standing at the highest point of the dune we had been walking behind. Behind us is the backdune and looking out toward the ocean is the toe, which slopes down toward the ocean. There can be many waves of dunes behind the foredune, rising and falling just like the ocean, “and they are all covered in grass.”
Varied Vegetation
“Backdune to toe, the density of grasses will change,” said Rebecca. And you can see other differences in other vegetation as well. Where we stood near the crest of the dune, we could see pearly everlasting, beach pea, native strawberry, and what was dubbed a “fun little thistle-y thing” growing between the blades of grass on the sand.
Not only that but, the species of beachgrass growing in an area also influences plant biodiversity. You see, in addition, to European beachgrass, American beachgrass was also introduced to the Pacific Northwest Coast to stabilize and protect coastal communities. However, for whatever reason, European beachgrass was introduced in the south and American beachgrass in the north, creating different beach grass ecosystems.
The differences in biodiversity between the American and European beachgrass systems is something that Sally Hacker’s Lab has studied in the past. When the lab compared the biodiversity of these dune systems, it was found that European beachgrass supports greater plant biodiversity than American beachgrass.
Two Ammophila Species
There are many additional differences between American beachgrass (Ammophila breviligulata) and European beachgrass (Ammophila arenaria) that make each type unique.
A. arenaria also has stems that are skinnier, leaves that are thinner, and a long ligule. The grass blades grow densely together; instead of sending out lots of lateral shoots, A. arenaria grows more vertically. In addition, A. arenaria “like to be in one clump together,” said Rebecca, allowing them to “accrete more sand” and build tall, steep dunes.
On the other hand, A. breviligulata has thicker leaves and stems and a short ligule. The grass blades grow further apart; instead of growing tall, A. breviligulata sends out lateral shoots and grows horizontally. According to Rebecca, a dune field of A. breviligulata is large and “hummocky.”
Hybridization
Though historically European beachgrass was dominant primarily in the South and American beachgrass in the North, on the Central Oregon Coast, where Rebecca and I were hiking, there is a point of overlap between the grass’s ranges. And, thus, an opportunity for hybridization, or the production of a genetic cross, between the two species.
“Part of my research is about the hybrid between these two beachgrasses,” said Rebecca, as she directed me down the toe and onto the sandy beach below in search of the first little hybrid patch she has been tracking. Rebecca explained that the first time the hybrid was “discovered” was in 2012.
“Discovered is a confusing word,” proclaimed Rebecca. “Some people from my lab were doing a survey and they found grass that looked sort of weird,” but it wasn’t until later, after finding more patches of the “weird” grass before it drew much interest. And later still before Rebecca was able to do the genetic work to confirm that what was discovered was a hybrid.
Taken for a Ride
We combed the beach looking for the “weird” hybrid. However, instead of finding it. we noticed many signs of storm damage—large swaths of sand torn from along the toe of the dune.
Rebecca walked over to one of the dunes and brushed away the sand from the base of one of the clusters of beachgrass. “Look here! You can see what it looks like under the sand,” she remarked holding a dense cluster of fibrous roots that branched out in all directions, connecting to other clusters of roots by underground stems.
“They erode from the beaches,” she said, “and it gets picked up by a wave and then gets spread from one beach to another.”
The Path Back
We continued looking along the beach, passing by the spot Rebecca recalled finding the hybrid in the past. The patch had since been washed away, perhaps to start up someplace new.
We headed inland toward another area Rebecca had GPS coordinates for, chatting along the way about her love of plants and how curiosity regarding invasive species led her to her work today. “Why do some plants get introduced and nothing happens?” Rebecca wondered aloud, reminiscing.
Rebecca’s passion for research was evident as we talked further. She told me how she got into genetic work in order to obtain higher resolution data that would allow her work to have a larger impact than in the past. “Genetic work is 100s to 1000s of data points,” she marveled.
Ultimately, Rebecca’s careful consideration of her interests and skills landed her in Sally Hacker’s Lab.
The Hybrid Problem
And then we were there, standing in front of a large path of hybrid beachgrass. “Here is its sweet little intermediate ligule,” Rebecca smiled as she pulled the leaf down on one of the grasses to reveal its “pit” tissue. “This is one of our wonderful patches,” she remarked, her gaze sweeping down at the bunches of grass that grew at our feet.
It was at this point that I asked Rebecca about the implication of the hybrid. “Is the hybrid a problem?” I questioned.
Even though they are not native to Oregon, explained Rebecca, beachgrasses are providing a service to people that live in coastal areas by protecting them from storm surges and erosion. However, “the two species produce different shaped dunes that have different value,” Rebecca explained. If the dominant species changes, that could mean a higher risk of storm surge to overtop the dunes, or it might not. She cited a 2010 or 2012 study that conversion to American beachgrass in areas where European dominates would create “a three-fold increase in overtopping risk.”
When it comes to the hybrid, there are a lot of questions to answer.
“What are its impacts going to be on the dunes? Is it going to build different shaped dunes? Is it going to take over areas of parent species?” Rebecca listed. “It’s kind of a dash to figure out the impact.”
More Invasive
There are also questions about how the hybridization might increase the invasiveness of the beachgrass species, potentially harming native species to a greater extent than the parent species.
“Hybridization can jump-start evolution in plants,” explained Rebecca. When separate species are put together you get something brand new— “a completely novel genotype!”
In addition, there is some evidence that the hybrid may be able to produce viable offspring, allowing for even more crossing of populations, increasing genetic biodiversity further. “Increasing genetic variation in invasive plants has been shown to increases their invasiveness,” said Rebecca.
To be Done
So, what can be done? “Can we stop or prevent the spread of invasive species?” I asked Rebecca, as we stood considering the potential impacts of her newly identified cross.
“There are a lot of layers to think about,” Rebecca suggested. Questions regarding who is being impacted and how will help determine an appropriate course of action. She used the example of cheatgrass, pervasive invasive grass in rangeland environments. The impacts of cheatgrass affect ranches and those that depend on the work the ranchers are doing, as well as the native plants and animals that live in the ecosystem. Thus, figuring out how to prevent the spread of cheatgrass is a high priority in the west.
With beachgrasses, it is a bit different. Again, despite some of the ecological ramifications, the presence of the grasses is needed in human-inhabited coastal areas as protection.
However, there are some efforts to remove the beachgrasses and restore some of the native habitats that have been virtually eliminated on the Pacific Northwest Coast with the introduction of the grasses. In fact, Rebecca shared how her advisor, Sally Hacker, is involved in some research looking into how to best restore some areas of the dunes that aren’t critical to coastal protection.
“When you think about the impact,” said Rebecca, “we should all be on board to keep invasive species in their lane.”
Three of a Kind
At this point, Rebecca and I headed back down the path toward our vehicles. Then, looking out in the distance, Rebecca pointed out a large dune that sat just in front of a line of houses.
“It is covered in hybrid,” she said, “and has all three species.”
Rebecca went on to explain how, instead of a natural system, the dunes in the area are actively managed—built up and planted by people—and suggested that we take a quick look. So, when we got back to the trailhead, a short walk later, we both hopped in our vehicles, and I followed her over to see what the fuss was about.
Upon arrival, we were able to find our first sample of American beachgrass with its short ligule. We also saw more European beachgrass, some American dune grass, and, of course, a lot of the hybrid.
Rebecca told me that so far, they have found more than 27 patches of the hybrid at 17 different sites heading North from Pacific City. The site we were visiting was the southern terminus of its extent so far.
And there was a lot of it! Rebecca pointed out the patches as we walked back onto the dune and looked around. There is so much of it, that Rebecca told me that they were in the process of training people to identify the hybrid as part of a Citizen Science Project.
We didn’t stay long on the managed dune, but Rebecca helped me gather a sample of the European beachgrass, American beachgrass, and the Hybrid. We lined them up and snapped a picture of all three for comparison.
A Bleak or Bright Future?
Looking at the photo now, with the hybrid placed alongside its parent species, I feel a bit like I am looking at a photo of a high school graduate with their proud parents.
We know a good deal about the European beachgrass and American beachgrass, they are settled in the habits of building dunes in the same way they always have, but the hybrid is something new—a fresh mix of genes with so much potential. The future of the hybrid could very well change the Pacific Northwest Coastline, for better or worse. Many questions remain. And a lot of opportunities await. Fortunately, we have people like Rebecca here to help us understand its future.
Rebecca Mostow is a Graduate Fellow at Oregon State University in Sally Hackers Lab studying dune ecology. She has also worked as an environmental educator and research technician. She earned a Bachelor of Arts in Biology from Oberlin College in 2013.