SPEAKER_03 0:01

Uchin uprising. Who really destroyed California's kelp forests? Have you ever thought about eating a purple sea urchin? What if I told you that eating them might actually help save an entire ecosystem?

SPEAKER_05 0:17

Picture this. You're a diver off the coast of Northern California. You drop below the surface expecting to see towering columns of kelp, shafts of filtered sunlight cutting through the green, fish weaving through the fronds, sea otters floating lazily above you. It's one of the most biodiverse ecosystems on the planet. But instead, you land on the seafloor and all you see is purple. Thousands upon thousands of spiny purple sea urchins. No kelp, no fish, just urchins. As far as I can see, slowly scraping the rocks clean.

SPEAKER_03 0:56

Welcome to Uchin Uprising. Who really destroyed California's kelp forests? I'm Kyra. I'm Felicity, and I'm Natalie. Today, we're gonna take you deep into one of California's most urgent ecological crises and challenge everything you think you know about who or what is actually responsible.

SPEAKER_05 1:17

So the question is, how did we get here? And more importantly, are sea urchins really the villain of this story?

SPEAKER_03 1:24

Part two. Introducing the pest. So let's start with the organism at the center of this story. Stronglocentrodus purparatus, the purple sea urchin. Natalie, can you give us a quick bio?

SPEAKER_05 1:41

Sure. The purple sea urchin is a small spiny marine invertebrate native to the Pacific coast of Northern America. It ranges from Alaska all the way down to Baja California, and it can live up to 70 years in the wild. They're grazers as they eat kelp and algae. Kelp itself is a type of large brown algae, and under normal conditions, purple sea urchins play an important ecological role by helping regulate algae growth without destroying the entire kelp forest.

SPEAKER_04 2:09

And that's a key phrase, right? Under normal conditions, because the purple sea urchin is native to these waters. It's not invasive, it's been part of this ecosystem for millennia. The question our podcast is really asking is what made this native species suddenly become the villain?

SPEAKER_03 2:26

Exactly. And I want to play a clip right now because when I was doing research for this project, I actually got to sit down with Dr. Sean Craig, a professor of zoology and marine biology, who studies kelp ecosystems and marine invertebrates. And I asked him that exact question. Here's what he said.

SPEAKER_00 2:46

There's nothing unusual about purple urchins. The problem is that we've removed some of the last predators, some of the last checks on their population growth. And so they're and and just by chance, as as as bad luck would have it, the factors that are causing their population to increase are really going well, right? So their populations are doing too well. Yeah.

SPEAKER_03 3:10

Doing too well. I love that framing. He's not saying urchins are bad, he's saying the system around them are broken.

SPEAKER_05 3:20

And that's such an important distinction. Because when you read headlines like this, and we'll talk about a lot of that today, about how media frames the story, you get language like verocious urchins ravaging cow forests, or the New York Times calling them a spiky, hungry foe. That language implies agency. It implies the urchins cl chose to destroy things.

SPEAKER_04 3:43

But ecologically, they're just doing what they do. The bigger question is what happened to everything that used to keep them in check.

SPEAKER_03 3:50

Part three: the ecosystem and how kelp forests work. To understand how this all unraveled, we need to zoom out and explain what a healthy kelp forest actually looks like. Felicity, why don't you take us there?

SPEAKER_04 4:06

Okay, so imagine a forest, but underwater. Kelp forests are among the most productive and ecologically important marine ecosystems in the world. They support rich biodiversity, sustain fisheries, and help regulate climate by acting as massive carbon sinks. Thousands of species depend on them, fish, invertebrates, and marine mammals.

SPEAKER_05 4:27

And sea otters are a huge part of the story. Sea otters are what ecologists call a keystone species. That means they have a disproportionately large impact on their environment relative to their numbers. And their main diet, sea urchins. A single sea otter can eat up to 25% of its body weight in food every single day.

SPEAKER_03 4:48

So you have this beautiful system. Otters eat urchins, urchins eat kelp in moderation, kelp forests thrive. Ecologists call this a trophic cascade, a chain reaction through the food web where the presence or absence of one predator ripples all the way down.

SPEAKER_04 5:06

And sea otters aren't the only check on urchin populations. There's also the sunflower sea star, also known as the Pygnopodia helianthoids, a large fast-moving predator that hunts sea urchins. These sea stars can grow up to three feet across and use hundreds of tiny tube feet to move surprisingly quickly across the ocean floor. When they catch an urchin, they pry it open and extend their stomach out of their body to digest the urchin externally. A single sunflower sea star can eat more five urchins a week, making them one of the most important natural predators, keeping urchin populations under control. Research has shown that in areas with more sunflower sea stars present, urchin grazing rates go down significantly.

SPEAKER_05 5:52

So you've got this system with multiple layers of protection. Otters from above, sea stars from the sides, and as long as those predators are there, the cult forests are fine. Purple urchins are grazing, yes, but within limits.

SPEAKER_03 6:06

Now, here's where the story begins to fall apart. Part four, the collapse. What happened starting in 2013? Around 2013, multiple things started going wrong at once. And I want to be really careful here, because this is actually where the science gets complicated. And where Dr. Craig said something really important I want to highlight.

SPEAKER_00 6:36

So what happened? The warm water came up along the coast. Yeah. The all the many of these uh sea stars died. The kelp disappeared. The urchins increased in number, the purple urchins, especially. Yes, we it is logical, and it may well be that the purple urchin increases the kelp beds, and that's the reason. Because they were freed up from lack of predators. But you know, all it all happened at once, and so it wasn't a good science experiment because it had multiple different things happening at the end.

SPEAKER_04 7:08

So first the blob. In 2014, an enormous marine heat wave, nicknamed the blob, warmed coastal waters along the Pacific. This weakened Kelp directly, making it vulnerable to grazing. Kelp doesn't love warm water.

SPEAKER_05 7:23

Then, almost simultaneously, sea star wasting disease hit. Starting around 2013 and peaking in 2014 and 2015, this disease caused massive die-offs of sunflower sea stars along the west coast. Sea star wasting disease is a syndrome linked to denzovirus infections and environmental stressors such as unusually warm ocean temperatures during the marine heat wave known as the blob. Infected sea stars developed lesions, lost limbs, and eventually disintegrated, devastating populations of one of the purple sea urchin's main predators. A study from UCSB's Marine Science Institute shows that purple sea urchin populations exploded between 2014 and 2022, directly following the sea star collapse. With the kelp canopy gone, light levels shifted and turf algae began replacing the complex habitat that once supported filter feeding invertebrates.

SPEAKER_03 8:50

That mattered because sea otters are a keystone predator. They eat sea urchins and help prevent urchin populations from overwhelming kelp forests. Recent research from Nicholson and colleagues actually found that areas where sea otters had rebounded showed much greater kelp forest resilience over the past century, even during periods of ocean warming and environmental stress. In fact, sea otter density was identified as one of the strongest predictors of healthy kelp canopy coverage.

SPEAKER_04 9:20

The NSF has summarized this really well. There are research says that small behavioral or environmental changes can tip a system between a kelp-dominated forest and an urchin baron, what scientists call a regime shift. And these shifts aren't easy to reverse.

SPEAKER_05 9:38

The scale of the collapse is staggering. About 95 to 96% of Northern California's kelp forests have disappeared over the past decade. 95%. That's not a local problem. That's a catastrophe.

SPEAKER_03 9:52

And this is where the pest story really kicks in. Because once the kelp was gone and once the economy started hunting, suddenly the urchins became public enemy number one. Part 5.

SPEAKER_04 10:09

Okay, so we need to talk about something that genuinely blew my mind when I first read about it, and that is called Zombie Urchins. This is so real. It is. An NPR piece by Lauren Sumner coined this term, and it describes something that makes purple sea urchins incredibly difficult to deal with. Basically, when there's no food, most animals die. But purple sea urchins have evolved the ability to enter a kind of low metabolism starvation mode. They shrink in size, they reabsorb their own tissues, they drop their metabolic rate dramatically to survive on almost nothing.

SPEAKER_03 10:43

And here's what makes this especially frustrating for kelp recovery. Even these starving, shrunken urchins will still graze. If even a tiny kelp sprout starts to grow, the zombie urchins mow it down before it has a chance to establish. Dr. Krape described this really vividly.

SPEAKER_00 11:02

If kelp spores begin to grow up, well, okay. As long as they're there and they're they're moving and still eating, they'll mow it down again. So, you know, so one of the one of the interesting things that's sort of indicated by that term zombie urchins is that they're changing their behavior, right? Their normal behavior for an urchin would be to sit in a crack or crevice and hide from its predators and just extend out its tube feed and capture some drift algae and eat that way. And that doesn't involve mowing down whole kelp bits, right? So part of the problem is clearly a shift in behavior.

SPEAKER_05 11:41

And their anatomy actually changes under starvation. Research shows that when urchins are deprived of nutrition, they reallocate energy away from reproduction and towards developing a more elongated jaw structure, literally evolving their teeth to scrape whatever they can from the seafloor.

SPEAKER_04 11:59

So you have millions of urchins that won't die, won't reproduce, can't be fattened up for market because they're starving and will destroy any cub that tries to grow back. That is genuinely a nightmare scenario for restoration.

SPEAKER_03 12:12

The California Sea Grant puts it well. Their ability to enter this low metabolism starvation mode is exactly why they're so hard to control. They're basically waiting it out. Part 6. Okay, so we've laid out the ecology. Now let's talk about something that's really central to our argument: how this crisis gets told. Because science is one thing, but the stories we tell about science shape policy, funding, and public behavior.

SPEAKER_05 12:46

And the dominant story about the sea urchin is not very nuanced. Headlines call them verocious. The New York Times published a piece titled How to Revive California's Underwater Forests. Smash a spiky hungry foe. They're quote unquote ravaging the coasts. They're invaders, they're villains. That's the thing.

SPEAKER_04 13:10

Urchins aren't invasive. They're not even misbehaving. They're native species responding to an ecosystem that humans fundamentally altered. Scholars like Kyle White have written about how environmental crises are often narrated in ways that obscure human responsibility. We displace the blame onto species, onto nature, rather than examining the economic and political systems that caused the disruption in the first place.

SPEAKER_03 13:34

A study by Rogers Bennett and Caton directly links the kelp collapse to the marine heat wave and human-driven climate change. But that's a harder story to tell, because it implicates all of us. Blaming the urchin is easier, cleaner, and honestly more emotionally satisfying.

SPEAKER_05 13:53

And this framing has real consequences. If the narrative is urchins are destroying the ocean, then the solution is kill the urchins. But if the narrative is climate change and predator loss created an ecological imbalance, the solutions are completely different and much harder.

SPEAKER_04 14:11

What's interesting is that from an academic standpoint, researchers like Stenek and Johnson have been writing for years about help forces as dynamic systems shaped by feedback loops. Purple sea urchins are not inherently destructive, they're products of a disrupted system. But that framing rarely makes it to the headlines.

SPEAKER_03 14:30

So we have this gap between the scientific understanding and the public narrative. And that gap shapes everything. Which interventions get funded, which species get protected, and whose livelihoods get prioritized. Part seven, the economic fallout.

SPEAKER_05 14:49

The economic consequences of the kelp collapse are enormous. Kelp forests aren't just ecologically important, they're economically critical. A 2023 study in Nature Communications estimated that fishery services in California kelp forests are worth up to 1.18 billion per year.

SPEAKER_04 15:11

And when forests collapse, that entire economy starts to unravel. One of the most dramatic examples is the Red Sea urchin fishery. Red urchins, the ones with marketable row or uni, depend on kelp for food. When kelp disappeared, red urchins harvests dropped to historic lows. A 2018 article in National Fisherman describes how purple urchins outcompeted red urchins for the remaining food, worsening the crisis for the fishing industry.

SPEAKER_05 15:54

There's also abalone. Abalone are marine snails that rely on drifting kelp for food. So when kelp forests collapsed, abalone populations suffered too. In Northern California, the Red Abalone fishery, once one of the most valuable recreational fisheries in the state, was forced to close in 2018 after mass starvation events and dramatic population declines linked to the loss of kelp habitat. At that time, purple sea urchins exploded in number, but ironically, many of them were starving too. The Guardian described this strange paradox in a 2021 article. There were too many urchins, but almost no marketable ones, because starving urchins developed tiny, low-quality gonads that are essentially worthless commercially. So the very abundance of purple sea urchins ended up hurting both the Avalone ecosystem and the urchin fishing industry itself. More urchins, less money.

SPEAKER_04 16:55

A segment from KALW Podcast covers the fishery collapse in San Francisco.

SPEAKER_02 17:04

That's bad news for Blake Tillman, who owns the Fort Bragg dive shop his father opened 40 years ago.

SPEAKER_01 17:10

Abalone diving is like a main been a main part of our business for years, and uh yeah, we're way our numbers are way down, obviously.

SPEAKER_02 17:19

Most years, Northern California has the largest recreational abalone fishery in the world. People come from all over to dive here. One study estimates that it's worth 44 million dollars. But this year the state says no one can dive for abalone. They've closed the season until 2020 to give the abalone a chance to grow back. Abalone are like canaries in a coal mine. They're one of the first species in the ecosystem to be affected by the colossal.

SPEAKER_01 17:48

This year I would say it's so dramatic. I'd say it's probably like 75% down as far as like people coming. That's pretty huge. But uh, I mean, we we offer other stuff at the shop, so that's kind of helping us.

SPEAKER_02 18:03

Dive shops are more than places to buy gear. They're like the office water coolers of the diving community. Hubs for news and gossip. While we're talking, a steady stream of divers comes in to fill up tanks.

SPEAKER_01 18:15

I got a lot of friends that are business owners in town, and they're all definitely feeling it.

SPEAKER_02 18:20

So diving tourism is slow, and commercial divers don't have work either.

SPEAKER_04 18:25

The irony is almost cruel. The species that's being blamed for destroying the economy is also the species that the economy theoretically could have been built around, if only someone could figure out how to fasten them up.

SPEAKER_03 18:37

Part 8. Solutions. From harvesting to predator reintroduction. So now let's talk about what people are actually doing. Because there's a lot happening and it's actually a really fascinating mix of ecological science, entrepreneurship, and government policy.

SPEAKER_05 18:56

The most direct intervention is urchin removal. The California Fish and Game Department allows commercial divers to harvest 40 gallons of purple sea urchins with no possession limit, an unusually permissive policy designed to reduce urchin populations. In 2022, the California Ocean Protection Council ran an urchin removal pilot project on the North Coast, employing commercial fishermen to remove urchins while diving, and early results were promising enough that they planned to scale it statewide.

SPEAKER_04 19:28

There's also a really fascinating economic angle here: the idea of urchin ranching. Companies like Uchinomics have been collecting, starving, low-quality urchins, fattening up in controlled environments by feeding them kelp and then selling them as premium seafood. A UCU Santa Barbara, a brand school project called Unicado, explored the same concept, turning purple sea urchins from an ecological problem into a gourmet product.

SPEAKER_03 19:57

And there's even scientific research at a commercial scale on this. A 2026 study in aquaculture by Xavier Smith and colleagues tested urchin row enhancement aquaculture at a commercial scale, showing real potential for turning these urchins into a sustainable resource.

SPEAKER_05 20:17

The Nao Center for Marine Science had developed what they call a bold kelp recovery plan, hiring divers to harvest purple urchins, raising them to create marketable uni, and using the profits to plant new kelp seed lines. It's designed as a self-sustaining economic model so it doesn't depend on endless grant funding.

SPEAKER_04 20:38

And on the Predator reintroduction side, NOAA Fisheries published a major story just this year about scientists breeding sunflower sea stars in captivity, specifically to reintroduce them to California's coastlines. That is huge. Sea otters are also recovering slowly, and a return to certain stretches of coastline have shown promising signs for kelp recovery. But it's controversial because sea otters eat more than just urchins, and some fishermen don't want them competing for their catch.

SPEAKER_03 21:07

Dr. Craig actually had a really strong opinion on what intervention should be prioritized. Let's hear from him. Yeah.

SPEAKER_00 21:14

It's a hard thing because you know the one thing I've avoided here, which I shouldn't have, is is you know reintroducing otters to some stretches of California. That is very controversial because the otters don't eat just urchins, right? They eat other things, and the fishermen don't want them to eat their five owls, for example, that they are growing. So that's tricky. Um but again, I think we need more experiments, more more applied, you know, kind of uh restoration projects and experiments to figure out what works and what doesn't and what scales and what doesn't. Um because you know what's the alternative? Well, the alternative really is no kelp beds on the coast of California, and it's hard. You know, we've got generations of people who literally grew up uh going out abalone diving, free diving, going with their father abalone free diving. It's kind of a way of life, right? And I'm just talking about, you know, recent people, Native Americans do no doubt have records of this too. So should we, you know, should we wish to go back to where we were before, um, I think something more radical is needed.

SPEAKER_05 22:30

What I find so interesting about all these solutions is that they're not just ecological, they're also economic and political. The California Kelp Restoration and Management Plan explicitly balances conservation goals with fishery interests and coastal community needs. And what I find so interesting about all these solutions is that they're not just ecological, they're also economic and political. The Kelp Forest, the California Kelp Restoration and Management Plan explicitly balances conservation goals with fishery interests and coastal community needs. In California's Senate Bill One C level rise adaptation grant program is funding coastal ecosystem resilient projects, including Kelp restoration. The crisis has become institutionalized, turned into policy, budgets, and governance structures.

SPEAKER_04 23:21

And that's exactly the framework that researchers like Satorius and colleagues have been thinking about how climate adaptation works best when scientists, government, and local communities actually collaborate rather than working in silos. When commercial fishermen, marine biologists, and state agencies are all in the same room, better solutions emerge.

SPEAKER_03 23:42

Part nine the bigger picture, what this really means. So let's bring this home. What is this story really about?

SPEAKER_05 23:51

It's about how we assign blame during an ecological crisis. The purple sea urchin didn't cause climate change. It didn't hunt the sea otters to near extinction. It didn't give sea stars a wasting disease. It's a native species that was freed from its natural constraints by a combination of forces that humans either caused or amplified.

SPEAKER_04 24:11

A paper by Stenick and Johnson frames it beautifully. Cope forces are dynamic systems, and sea urchins are products of human environmental impact rather than inherently destructive organisms. The question isn't how do we stop the urchins? The deeper question is how did how did we break the system that kept them in balance?

SPEAKER_03 24:30

And Dr. Craig ended our conversation with something that really stuck out to me. I asked him, if nothing changes, what does California's coast look like in 10 years?

SPEAKER_00 24:41

Yeah, right. Um, well, I think if yeah, it's kind of a sad question. I think if nothing changes, right? If we keep cranking out CO2 into our atmosphere, if we keep refusing to even, you know, utter the words climate change, let alone recognize it's happening and ongoing and has been for quite a while now, if we don't change, you know, the fact that we are warm in the globe, then there's going to be more and more heat waves that more and more of them are going to hit the California coast. More and more of the kelp beds are going to disappear. More and more of the urchins, maybe, are going to increase to a point, right, where they literally have lived in a zombie kind of fashion for years. And then maybe they die too. And, you know, we're going to be left with not so functional ecosystems, right? Not so good fisheries, uh, not so many, uh not as many, at least, sources of food, employment. Um, we're gonna end up paying ourselves for this problem if we keep ignoring it, and it's gonna be much more expensive down the road. Yeah. It's gonna be much more catastrophic down the road than we're even imagining right now, right?

SPEAKER_05 26:02

Purple sea urchins are not the villain of this story. They're a symptom, a signal. The real story is about what happens to ecosystems and to communities when we fail to reckon with climate change and the fragility of the ecological relationships we depend on.

SPEAKER_04 26:17

And there is hope. The research on sunflower sea star restoration is promising. Urchin aquaculture is creating new markets. Celp forces have shown that they can recover quickly when urchin numbers drop. One study found that rocky reefs returned to kelp-dominated conditions just after six months after an urchin die-off and stayed at way for five more years of monitoring. These systems want to heal. They just need the conditions to do it.

SPEAKER_03 26:43

Part 10. Closing and call to action. So next time you see a headline calling urchins voracious invaders, or next time you're at a sushi restaurant and the chef tells you about Uni, we hope you'll think about the bigger story about trophic cascades, zombie urchins, climate-driven collapse, and a tiny spiny creature that's been living on this coastline for millions of years, simply trying to survive.

SPEAKER_05 27:11

If you want to help, eat Purple Sea Urchin Uni when you can find it. Support California's couple restoration efforts, and pay attention to the policies that shape how we manage our coastlines.

SPEAKER_04 27:23

The Purple Sea Urchin Crisis is at its core a story about us, about human choices, human systems, and whether we can take responsibility for the ecosystems we've disrupted.

SPEAKER_03 27:34

Thank you so much for listening to Urchin Uprising. I'm Kyra. I'm Felicity. And I'm Natalie. We'll see you underwater.