Only a third of Oregon’s kelp forests remain

A report from the Oregon Kelp Alliance found that nearly two-thirds of the state’s kelp forests have died out over the last decade. A multitude of factors appear to be behind the decline, including rising ocean temperatures and booming populations of purple sea urchins, which eat the kelp. The report also outlines future research and conservation strategies that could help protect the state’s remaining kelp forests.

Sara Hamilton is the scientific coordinator for the Oregon Kelp Alliance and one of the report’s lead authors. She joins us to talk about the status of Oregon’s kelp forests and what it could mean for coastal communities and ecosystems.

Note: The following transcript was transcribed digitally and validated for accuracy, readability and formatting by an OPB volunteer.

Dave Miller: From the Gert Boyle Studio at OPB, this is Think Out Loud. I’m Dave Miller. Nearly two-thirds of the kelp forests off the Oregon Coast have died out over the last decade. That is the headline from a recent report put out by the Oregon Kelp Alliance. A number of factors appear to have caused this decline, including rising ocean temperatures and booming populations of purple sea urchins, which are voracious kelp eaters. But the report also outlines some conservation strategies that could help protect the state’s remaining kelp forests and ideally bring some back.

Sara Hamilton is a scientific coordinator for the Oregon Kelp Alliance and one of the report’s lead authors. She joins us now. It’s great to have you on Think Out Loud.

Sara Hamilton: Thank you so much for inviting me here today, Dave.

Miller: For folks who may not have heard some of our earlier conversations about kelp forests, can you just first remind us what they are?

Hamilton: Yeah, so kelp forests, [like] the way that on land, the presence of trees creates an ecosystem, creates a forest, in the ocean, the presence of kelps – these large brown seaweeds – creates a kelp forest. It is its own ecosystem with unique animals that live there and utilize that ecosystem, and they provide a lot of ecosystem services to coastal communities.

Miller: Am I right that among other things, you are a diver?

Hamilton: Yes, I am.

Miller: What’s it like when you are swimming in and around, up and down, an intact kelp forest? What does it look like? What does it feel like?

Hamilton: Some of my best dives in kelp forests, I’ve kind of been down at the bottom, looking up at the way the light streams through the kelp on the canopy. And it always reminds me of like an underwater cathedral. You almost feel like you can hear angels singing, or a choir or something, the way the light diffuses through the kelp, all the fish and the life around you. Yeah, it’s really inspiring.

Miller: What do they mean ecologically?

Hamilton: From my perspective, one of the most important things about kelp forests is that there are these incredible biodiversity powerhouses. They are home to all sorts of different animals, from red sea urchins and abalone to rockfish and lingcod, all the way up to gray whales. Recent work at Oregon State University has found that the prey that gray whales like to feed on preferentially spends time in kelp forests. So kelp forests, you’re even connected to gray whales.

So they support diverse fisheries because of all these animals that live within their bounds. They provide all sorts of cultural and recreational opportunities. They convert a tremendous amount of carbon in seawater into organic carbon. They can buffer coastlines from waves, ocean ossification and other impacts of climate change.

Miller: How did it first become obvious that Oregon’s kelp forests were in trouble?

Hamilton: Well, I think one of the interesting things about this story is that, historically, there hasn’t been a lot of formal monitoring of kelp forests here in Oregon. And so it wasn’t actually scientists or managers that first started noticing it. It was fishermen, and it was specifically urchin divers. The red sea urchin fishery is the third largest shellfish fishery in Oregon. Sea urchin divers started coming in and reporting that these kelp forests that they had worked for decades, were just completely gone. They couldn’t fish there anymore and they didn’t know where they were going to fish now. So, those were really the first people to start raising alarm bells about this.

Miller: How long ago was that?

Hamilton: Gosh, that started in 2018 or 2019, so it’s taken a while to spin up an apparatus to be able to actually investigate this.

Miller: I mean, that seems like anecdotes. How much actual data was there at that time about Oregon’s kelp forests?

Hamilton: The state of Oregon, the Department of Fish and Wildlife has historically done aerial surveys of kelp coverage, because since some of these kelp species can reach the surface, you can actually see them from planes. And when we first started getting these anecdotal accounts around 2018, 2020, there hadn’t been a kelp survey conducted by the Department of Fish and Wildlife since 2010. So it had been about a decade at that point. So we had very little information to fact check the anecdotes and understand how widespread of a problem it was.

Miller: At that time, what had you been hearing from your counterparts, though, in California, Washington or B.C.?

Hamilton: Yeah, so this is not a problem unique to Oregon. Globally, kelp forests are in trouble. We knew that starting around 2014, 2015, there had been a really serious collapse of Northern California’s bull kelp forests. In fact, they lost about 95% of their bull kelp forests around that time. So we knew that from Northern California, to Australia, to Norway, there were so many places where kelp forests were showing declines and even disappearance. We were primed to find out that these anecdotes were correct. It kind of made sense in the context.

Miller: Can you describe how this coalition set out to get better information in the last couple of years about the state of the state’s kelp forests?

Hamilton: I’m the one here talking about this today, but this was a huge team effort. We worked with dozens of collaborators and data contributors. Specifically, we worked with scientists at the Oregon Coast Aquarium, the Oregon Institute for Marine Biology and Reef Check – which is a nonprofit – to go do those scuba surveys. We conducted about 170 scuba surveys in 2023, targeting all these places that we knew historically had kelp forest habitat. So just the divers alone was a team of 12 people from multiple different institutions to make that work.

Then we were also working with scientists from Oregon State University, from the Oregon Department of Fish and Wildlife. The kelp forests occur up and down the coastline, so we had to work with people up and down the coastline, and it really quickly became a big team effort to be able to pull this off.

Miller: What’s the big picture view of how the state’s kelp forests have been faring?

Hamilton: The big picture is that, as you mentioned, about two-thirds of our kelp forests have been lost in the last decade or so. Many of the places where we have lost kelp forests are now urchin barrens. So you go down there and there’s no kelp. There are very few things growing, there are very few animals. It’s really kind of just the spiky urchins lining the floor of the ocean.

Miller: How are those urchins surviving if the stuff I thought were munching [is] gone?

Hamilton: Urchins are incredible animals. They blow me away, as frustrating as they are for some positions. So they actually are evolved to deal with periods without a whole lot of food resources. One of the things that they do is when the kelp goes away, they actually ramp down their metabolism and can go into a semi-hibernation state, where they don’t need much food at all to persist for a very long time. Up to 16 months they can go without any food at all because their metabolism is so low. So, they get a little bit of food here, a little bit of food there, and they can end up persisting in these urchin barrens for years and years at a time, which can make it very hard to get yourself out of this urchin barren and re-establish that kelp forest.

Miller: Right, because one could have thought that one possibility was that it would sort of work itself out. The munchers would die off and give the kelp a chance to regrow, but it seems like urchins evolutionarily have figured out a way around that, at least for some number of months or years. What are the other reasons for the decline in kelp, in addition to the boom in urchins?

Hamilton: Globally, we know that when water temperatures increase, when it gets warmer, kelps suffer, and that is because kelps are fundamentally a temperate species. They thrive in cool, nutrient-rich waters. When waters get warmer, it stresses them out thermally and there tend to be fewer nutrients in the water for them to grow. So marine heat waves and long-term ocean warming in many parts of the globe have been a driver of kelp forest loss, as well as other aspects of climate change – places getting stormier, places getting increased sediment runoff and now there’s no light.

So it’s very likely that how climate change is changing the physical and chemical nature of our oceans is playing a role in what’s going on here in Oregon. But there really hasn’t been enough research for us to kind of put our finger on one specific thing, as far as some of those environmental factors go.

Miller: In terms of the urchins, to go back to them for a second, we’ve talked in the past about the sunflower sea star, an urchin predator, the populations of which have been devastated by a wasting disease in recent years. Are there continuing signs of potential recovery for these sea stars?

Hamilton: One of the really exciting things about this report and one of the really exciting things for me as a scientist in 2023 was that, for the first time in a decade, all of a sudden, we were getting calls from people who were saying, “I found a sunflower sea star here. I found a sunflower sea star there. I found 20 juveniles off of the Newport jetty.” So, in 2023, we first documented this sudden kind of surge of sightings of sunflower sea stars in Oregon, for the first time since wasting disease hit. And I’m really pleased to say that in 2024, we actually documented even more sunflower sea stars than we did in 2023. A lot of that was through observations of just community members. So it was (a) really exciting that there is hope for this predator in Oregon; and (b) so gratifying to get to work with community members to document this exciting kind of late breaking finding.

Miller: Do you have any idea why the numbers are rebounding?

Hamilton: Oh, that’s a great question. I’m not sure we really do yet. One thing to note is that further north in their range … sunflower sea stars go all the way up to Alaska. While in California, Mexico and Oregon, the species was nearly wiped out by sea star wasting disease, it wasn’t as severe further north, for instance, in British Columbia. So it could be that populations were so low here for a long time that there weren’t a lot of adults to reproduce and we just kind of got enough population momentum going that suddenly some are showing up now. But we don’t know. We don’t know a lot of things about these animals and about this disease.

Miller: Are there any areas on Oregon’s coast where kelp appeared to be doing well, places that could provide both hope, just for the present, but also an idea of a pathway for the future?

Hamilton: Yeah, there totally are. And it’s so important to note that, yes, it’s really sobering to realize that we’ve lost about two-thirds of this ecosystem in Oregon. But that also means that about one-third of it is still left. So some of the places that you can still see vibrant, happy kelp forests include Depot Bay, just north of Newport. That area actually had some of the strongest kelp forest coverage in 2023 that it’s had in the last couple decades. Cape Arago, down by Coos Bay, also has some really persistent stable kelp forests. And then Rogue Reef, which is off of Gold Beach on the south Oregon Coast. Those are all places that still have intact kelp forests and give us both hope for the future, as well as a reason to get up there and protect the resources that are still around.

Miller: Does something unify those three places? And is that something reproducible?

Hamilton: That’s a great question. We’re working on a follow-up paper right now to kind of look into whether there’s something about the temperature, or the salinity profiles, or the depth, or something like that in those areas that points to a reason why they’ve been resilient. But again, unfortunately, there’s so many spaces here where I have to say, we don’t actually know, we’re still working on that. It takes a long time to come up with good science around these systems, and we haven’t been doing that for the last couple of decades in Oregon.

Miller: Well, what can you or others do right now that you have a pretty good sense will actually help?

Hamilton: Yeah, so one of the great things about being a little bit behind the curve is that we get to watch what other places are doing in response to their kelp forest declines and learn from them. So we’ve been watching what they’ve been doing in Northern California, in British Columbia, in Australia. And trying to figure out, what have they been doing there to restore their kelp forest and how can we apply it here? So some of the things that have worked in other places that we want to bring to Oregon include controlling grazers, suppressing the number of purple sea urchins out there so that they’re not constantly grazing down the kelp forests we still have, or grazing up any new kelps that try to establish in an urchin barren.

Miller: Am I right that … When we talked about this years ago, an image that has stuck with me is that this could be as simple and sort of gruesome as just hitting them with hammers. Is that still the state of the art?

Hamilton: Yeah, I mean it sounds crude, but it’s very targeted. You don’t get any kind of bycatch, you don’t harm any other organisms down there. But yeah, one of the main ways we do that is we take hammers down there and we crush the urchins.

Miller: OK, so that’s step one, get rid of some of these herbivores and basically be the predators that there aren’t enough of in the wild. Humans can do that. What else?

Hamilton: Well, after you’ve removed some of those grazers, those urchins, you can then go in and basically outplant kelps. And you can outplant them at the baby kind of seed or spore stage, or you can outplant them when they’re small adults. So once the urchins have been cleared out, you need to get that kelp forest to reestablish. Seeding the little juvenile kelps out there is something that’s being used in Puget Sound, in several parts of California.

And importantly, both of those two strategies – urchin removal and kelp enhancement – tend to work at relatively small spatial scales. So we can’t do this across the entire coastline. There are too many urchins out there. So we have to kind of pick and choose these important places that are important to community members or important to abalone populations, to go in and focus a lot of restoration work on.

However, the two things that can work at a bigger spatial scale are, one, protecting the kelp forests that we do have, for instance, by working with commercial urchin divers to keep urchin densities low before they explode and graze down a kelp forest. And then, two, we need to get that predator or a predator back into the system. Historically, both sea otters and sunflower sea stars were present in kelp forests and can eat a lot of urchins.

So while humans can play that predator role in some places, we’re not going to be able to do it up and down the coast. One of the other, kind of bigger spatial-scale keys to restoring, protecting our kelp forests for generations to come, is going to be restoring sunflower sea stars or another urchin predator, to restore that food web balance in the system.

Miller: It occurs to me, as you’re describing all of this, the interconnectedness in terms of the humans involved here – six years ago or so, getting anecdotal reports from commercial fishermen that alerted you to what was happening with the kelp; finding out, in recent years, just from people living on the coast or walking on the beach, that they were seeing the return of sea stars. What’s it going to take in terms of human cooperation for this to work?

Hamilton: Yeah, that’s a great question. So I think one of the important things to realize is that it will take human cooperation, it will take volunteer divers. We work with organizations like Reef Check that recruit volunteers to go out and do surveys and remove urchins. We work with commercial urchin divers to harvest urchins, things like that.

So it will require cooperation, but there are so many benefits that coastal communities and coastal community members derive from kelp forests. One of the reasons that fishermen are involved is because kelp forests support the fisheries that are so important for a number of coastal communities. So I think coastal community members really see that it’s not a one-way street. It is about taking care of the ecosystems, so that the ecosystems can take care of the communities. And coastal community members really get that. It’s always so overwhelming how much support and how much interest we get from people about, “what can I do to help, how can I be part of this?”

Miller: Sara, thanks very much.

Hamilton: Yeah, thank you so much, Dave.

Miller: Sara Hamilton is a scientific coordinator for the Oregon Kelp Alliance.

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