Counting Carbon at South Beach State Park, Oregon
When you visit Oregon’s coast you may have noticed that it takes some effort to get down to the beach. Much of Oregon’s coast is characterized by large grass-covered dunes that separate inland areas from the sandy shoreline environment. So, getting to the beach often takes a little bit of a climb. This was not the case some 100 years ago.
Before European colonization on the Pacific Northwest coastline, much of what is now a dune system would have looked very different. Instead of walls of sand 15 meters high, a hummocky sand sheet would have stretched to the shoreline.
The dune landscape was created by people. In 1910, European beach grass (Ammophila arenaria) was introduced to the Oregon coast to stabilize and control areas of sand near human habitation. Later, in the 1930s, American Beach grass was also introduced.
These grasses are really good at capturing sand and building dunes. They are also really good at spreading via seed dispersal and rhizomatic growth. The result is the grass-covered dunes you see stretching down the coastline today.
So, how should we feel about this takeover?
I met up with John Stepanek, biologist, and Ph.D. candidate in Sally Hacker’s Lab at Oregon State University, at South Beach State Park to discuss these built dunes and what they mean for Oregonians now and in the future.
The Hike
- Trailhead: South Beach State Park Day Use Area (South Jetty Trailhead)
- Distance: varies (approx. 2 miles)
- Elevation Gain: minimal
- Details: No parking pass required. Ample parking at the trailhead. Restrooms are available. Access roads to the trailhead are paved. South Jetty Trail is a paved path.
Meet and Greet
The day was bright and warm when I met John in the parking lot at South Beach State Park. John had his dog with him, and both were friendly and welcoming, as we made our introduction and started down the paved South Jetty trail.
John told me how he grew up in California not really knowing what he wanted to study. He enjoyed biology in high school, and the outdoors, but it took him a while to find his path.
“I thought I would like to be a wildland firefighter,” John reminisced.
However, his love for biology, and specifically plants, grew while attending Cal Poly for his undergraduate degree. And eventually, he changed his major from Forestry to Biology.
Despite his love for plants, John’s early involvement in research was focused on reptiles.
“I studied rattlesnakes and blue-bellied lizards for three years,” said John.
It wouldn’t be until he came to OSU and joined Sally Hacker’s Lab that his attention would be drawn back to his love for plants, as well as a new focus of study—dunes.
Forested Dune Ecosystem
John and I continued down the wide path. On either side of us was a wall of trees and shrubs. I asked John with his expert eye to describe what we were seeing.
“We are in a forested dune ecosystem,” said John, his love for botany radiating forth.
“The main canopy is shore pine,” he went on, pointing to a rough-barked tree with long needles and a bent stature. “It is one of the only pines with two needles in each bundle.”
John went on to explain how shore pine is just a subspecies of a conifer that typically grows in the mountains, called the lodgepole pine. Grown on the coast it tends to be shorter and more gnarled, while in the mountains it grows straight and tall.
But shore pine is not the only canopy tree in the dune forest. Sharp-needled Sitka spruce is also often present. I noticed a few growing alongside the shore pine.
Soon John and I got to botanizing—noticing and pointing out all the plants on the trail.
“Ferns and grasses grow out here,” John stated. “Salal as well.” He pointed to the thick, large-leaved plant with an angular alternate arrangement.
Native plants, like evergreen huckleberry, twinberry, and our native beach grass were all identified, as well as non-native scotch broom and European beach grass.
“It is not super complex, at least not in the state it is in… the grasses have reduced the native biodiversity,” John explained. “There are a lot of different plants but there is low abundance.”
John showed me how to tell the native beach grass from the non-native varieties: “See how it has a bluish wax that you can rub off, and how wide it is with a prominent midrib?”
Charting the Dunes
It didn’t take long before John and I reached a trail heading left toward the beach. We decided to take it, to see what lay beyond the forested back dune (also known as the hind-dune).
John described the transition from the back dune heading toward the coast as being a bit like walking forward in time with the forested back dune being the oldest and the beach the youngest—a study in succession.
We moved forward—in space and time.
The Heel
As we entered the dune heel—the area just behind the dune closest to the ocean—the vegetation transitioned from forest to grass. Though European beach grass was dominant, many shrubs and small herbaceous species grew in this more sunlit environment.
John pointed out some young yarrow with its lacy leaves and beach strawberry trailing along the path edges. We also saw the radiating leaves of the seashore lupine (Lupinus littoralis).
“Pearly everlasting is common in summer,” John added.
Even sword fern, typically a forest plant, seemed to be surviving the harsh conditions—though its fronds were a bit battered and curled inward.
“How does it grow so many places?” John enthused—impressed by its adaptability.
Overall, it seemed the backside of the dune had a rich assortment of plant life. “This area is cut off from new sand deposits,” John explained, so “there is more biodiversity back here.”
The Crest
However, as we trudged up the steep foredune, the dune closest to the ocean, all of that changed. As we reached the crest—the highest point of the foredune—we faced a near uniform sea of European beach grass.
John explained:
“There is low diversity on the face of the foredune, where it is really only the grasses. The grasses build up a dune tall enough that it buries the other plants trying to grow and eventually creates a wall that prevents the sand from being blown further back.”
In short, European beach grass is too good at building dunes—nothing else can really keep up with the rate at which they collect sand.
The Toe
Coming down off the face of the dune, some biodiversity may be regained. Certain plants become more common on the toe of the dune—the far front end of the dune facing the water.
Though we didn’t see any on our hike, John sent me a list of these species common to the toe: yellow sand verbena (Abronia latifolia), pink sand verbena (Abronia umbellata), American sea rocket (Cakile edentula), sea rocket (Cakile maritima) and seaside sandwort (Honckenya peploides).
Storing Carbon
John and I hiked down the face of the dune to the beach to continue our walk.
As we walked the beach, John told me about his part in researching the dunes. You see, John doesn’t just study the plants in the dune ecosystem, he studies the carbon.
“Coastal ecosystems like salt marshes, estuaries, and mangroves are really good at storing carbon,” said John.
He went on to explain how carbon is stored through “two mechanisms.”
First, the vegetation in these ecosystems stores carbon via photosynthesis—essentially removing carbon from the atmosphere and storing it in their tissues, and later the organic matter in the soil after they die.
Second, is the storage of carbon in sediment that is washed in and settles in these tidal areas, building up a layer of organic matter. This organic matter sticks around, decaying very slowly—effectively storing carbon for the long term.
The problem is that though estuaries, tidal marshes, and mangroves are excellent carbon stores, they only make up a tiny fraction of the world’s coast—“up to 6%” according to John. While dune ecosystems, whose carbon storage potential has largely been overlooked, make up one-third.
Admittedly, dunes don’t seem at first glance likely candidates for the world’s greatest carbon sinks. The fact that they are mostly sand isn’t particularly encouraging. But that didn’t deter John from researching dune carbon—work he has been engaged in over the last four years.
Counting Carbon
This of course raises the question: How does one go about measuring carbon?
“We do a transect from the water back to the trees and shrubs,” John answered when I asked him that very question. A transect is simply a measured line from which data is gathered.
Then using a quadrat—a square made of PVC pipe that’s used to measure things in a certain area—the abundance and density of plants are measured at points along the transect, and samples of plants are collected. This data will be used to determine the “above ground carbon.”
Then, using a 4-inch PVC pipe and a sledgehammer, John takes cores along the transect as well. These cores go down 1 meter and are used to collect samples of “below-ground carbon.”
Once in the lab, samples are dried, weighed, and then burned at 550 degrees Celsius. Before and after weights of the samples are used to get a crude measure of organic matter—a decent proxy for carbon. Later, elemental analysis is done on some subsamples, as well, to determine the organic matter to carbon relationship.
The goal is to get an estimate of “the actual carbon stocks” found in dune ecosystems.
Findings
The sun reflected white puffy clouds as John and I hiked on the wetter, firmer sand on the beach, closer to the ocean’s edge.
I asked John what he has discovered so far. Was there any carbon in the sand below our feet?
In general, not a lot.
“Sand is mostly inorganic tiny rocks,” said John. “They don’t trap organic matter very well and there is a quicker rate of decomposition relative to materials like silt or clay.”
The highest value John has found in any of his sand samples is 10% organic matter. On average 4.4 kg of organic carbon per meter squared. These values are higher than desert sand and even higher than conventional agriculture, but on the low end compared to salt marshes and terrestrial grasslands, according to John.
“The highest in some other systems could be 80%,” stated John as a comparison. John mentioned mangroves and coast range forests—these would be many magnitudes more.
Of course, these values are per volume and per unit mass, and there is a lot of sand in the dune ecosystem. Therefore, despite the low percentage, the dunes are still providing a substantial carbon store. I mean, 10% of a lot is still a lot.
Patterns
Having gathered data from nearly fifty transects up and down the coast, John has also observed other patterns.
There are differences depending on latitude, type of dominant beach grass, distance from the shore, as well as vertically within core samples.
“There is more (carbon) near the surface,” John remarked, “—the organic horizon of the soil.”
Carbon also varies as you move through a transect—increasing as you move toward the back dune where the vegetation is more biodiverse and complex. The intertidal area is also typically a bit higher, around 1%, and the toe of the dune at something like 0.5%.
“Plants are the main driver of organic matter,” John explained. Thus, the further you move back from the ocean, the more carbon.
Ecosystem Services
I glanced up at the dunes to our right as we strode across the “mostly inorganic tiny rocks”—measuring the mass mentally, assessing the carbon.
Could these dunes help solve our climate crisis? Should we be building more dunes?
I didn’t ask John these questions. These are questions that John said that he commonly gets asked about his research.
The short answer is no.
He continued, “We don’t have all our results, but we expect that today’s dunes store more carbon than native systems would have done and trap more sediment,” but “the reason there is too much carbon in the atmosphere isn’t because we dug up the dunes.”
The dunes were not historically here. Though they provide some benefits, like storm and erosion protection, and even a little carbon storage, the pre-dune environment would have had its own set of benefits.
“Before these grasses were introduced, lots of native plants and animals were able to live here, and many Indigenous peoples would have managed this environment for ecosystem services important to them.”
Also, we do know that the dune ecosystems, as they exist now, have at least some drawbacks to wildlife.
John was adamant about balancing the services of the past and future.
“They do a great job protecting coastal development, but not so great when it comes to the flora and fauna,” John said. “It is about the collective good. Coastal protection is only valuable for those living right on the coast.” Does that mean it is best for everyone?
Carbon Stores
By now, John and I had reached the South Beach Jetty and turned inland, hiking up to the parking area to where we could loop back to our cars.
I asked John as we reentered the most carbon-rich back dune environment and eventually the forest: What ecosystems we should be looking out for, if not dunes?
“The temperate rainforests in the northwest coast range and west cascades,” was his unhesitating reply. Though he corrected himself a little—“old growth forests.”
John explained how carbon is sequestered in the mass of the old-growth trees, both above and below ground. He also made clear that high-density forests, like might be found on a tree plantation, are by no means comparable.
“Fewer large trees have more carbon than a bunch of small young trees,” John said.
He mentioned the work of Dr. Bev Law from the College of Forestry at Oregon State University as a source for these findings.
“Her work is showing the effects of the logging industry,” he continued.
Mangroves are another ecosystem John mentioned for carbon storage. Again, much of the carbon found in mangroves is stored in the tissue of the trees. In the case of mangroves, mostly below ground.
“Even in coastal ecosystems,” said John, “mangroves are an arm and leg above the others.”
Looping back
After meandering a while in the tall dune grasses, once again, we found our way back to the forested paved path. As we walked, we talked forward about the future—both in research and in life.
There are still many questions to be investigated when it comes to dune research. John mentioned being able to study the forested dune environment as being a good next step, though admitted he would not likely be the one to do the work.
He also described a strong curiosity to understand more fully the structure of the foredune—what it looks like several meters down. John rattled off several questions for starters:
“What does the root system look like? Are those roots and rhizomes all from the same plants? How has the water table changed? Is the carbon density the same deeper than a meter?”
Uncertain Future
John doesn’t know what he wants to do when he finishes his Ph.D.—though he expressed an interest in teaching, perhaps at a small 4-year school or community college.
But as he put it, “I haven’t taken other options off the table.”
The future is a tough thing to peg down.
The Pacific Northwest dunes and coastal environments also face an uncertain future. Climate change and human encroachment threaten these ecosystems and their functioning.
John hopes his research can help inform coastal ecosystem management. By understanding what we have now—perhaps we can mitigate against these threats and create a future worth preserving.
John Stepanek is a biologist and PhD candidate in Sally Hacker’s Lab at Oregon State University. He earned his Bachelor of Science from California Polytechnic State University where he majored in Biology.
