Zombies, it turns out, are real — and science journalist Mindy Weisberger can give you plenty of examples of them.

She’s read up on the fungi that take over flies’ bodies, partially digesting them from the inside out before forcing them to climb up blades of grass, so that fungal spores can explode out from their swollen corpses and claim new victims. 

She’s considered the hairworms that grow inside of crickets before inducing their hosts to toss themselves into a nearby body of water, where the worms emerge from the crickets’ exoskeleton in a miniature but all-too-real imitation of the alien in Alien. 

She’s even researched the snails that fall victim to certain flatworms. The flatworms’ larvae need to be eaten by birds to reach the next stage of their lifecycle, so broodsacs full of larvae take up residence in the snails’ eyestalks and turn them into pulsing, colorful, caterpillar-like bird-lures. The parasite also manipulates the snails into wandering into the open in order to increase the odds that a bird will spot the snails and devour both their eyestalks and the larvae within them. 

Weisberger dug into these specific nightmare-inducing examples of parasitic mind-control — and many others — as part of her effort to understand real-life “zombification” in her book, Rise of the Zombie Bugs. What she found was that these natural zombie stories are not only sources of inspiration for horrifying fiction — they could also inspire researchers who are trying to better understand everything from immune responses to pest control. 

So we spoke to Weisberger about research on real-life zombies for Unexplainable, Vox’s science podcast. What follows is a version of our conversation, edited for clarity and length. There’s much more in the full podcast, so listen to Unexplainable wherever you get podcasts, including Apple Podcasts and Spotify.

Let’s start by just defining some terms. What do we mean when we say “zombifier,” or “zombie”?

A zombifier is an organism that manipulates the behavior of its host, and a zombie is an organism that is being manipulated to behave in a way that it normally would not, and which only benefits the parasite that’s manipulating it. 

Let’s say you catch a cold — you’re gonna change your behavior because you’re feeling sick. You feel like you need to rest more, you need to drink more water. These are all things that help you recover, that help you fight off the infection. So in a certain sense, that’s the cold virus generating a change in behavior, but it’s a behavioral change that actually benefits you. 

For a zombie, the changes to its behavior are not something that benefit the host. They only benefit the parasite. That’s what makes it a zombie.

So it’d be like if I got sick and instead of going into my room and trying to sleep it off, I went and I licked everybody that I could lick in order to spread it. 

Yeah, exactly. There are zombifying viruses; there are zombifying fungi; there are insects that are able to zombify their hosts. There are worms that can zombify their hosts. Most of the organisms that they infect are arthropods — bugs. (I do have to apologize to entomologists, because as far as entomologists are concerned, bugs are only insects with sucking mouth parts. However, as we all know, colloquially, “bugs” covers a much broader range.)

What are some of the biggest categories of mysteries about how [zombifiers do what they do]?

Some of the biggest mysteries start with the moment that the host is infected, because obviously a body’s first response to any kind of infection is going to be an immune response. The first thing that a zombifier needs to do is to somehow get past that. That’s a big question for zombifiers, from viruses to wasps to fungi to worms: When they get inside an organism where they’re not supposed to be, how exactly are they telling their host immune system, “No, there’s nothing to see here! Just go about your business! You don’t need to worry about me!” 

Another one is, once it gets to the point of manipulation, what are the cues? How does it decide “Okay, now’s the right time to get this host moving to a place where I need to be”? 

The third big question is obviously the nuts and bolts of: How is it manipulating behavior? The thing about this field is that there is still so much that scientists are piecing together about the precise mechanisms of how this works. Behavior is something that is just super complicated, even in insects.  

So, when we look at, for example, the wasp that parasitizes orb-weaving spiders, scientists have found that in the spiders that are zombified,  what the wasp does — it lays an egg on the spider. The egg hatches, and the wasp larva essentially piggybacks on the spider and drinks from it like it’s a living juice box.  

And the spider just goes about its business until the larva is ready to reproduce. And then somehow the wasp larvae is manipulating the spider to think that it’s time to molt, so that the spider makes a different type of web than it normally does, something called a resting web. It’s reinforced, and it’s meant to support the spider and protect the spider while it’s molting. 

And then once that web is done, the wasp larvae drains the spider dry, the spider’s empty husk of a corpse drops to the ground, and the wasp larva builds its cocoon and sets itself up in the spider’s final web to hang out until it becomes an adult wasp.

What scientists found is that when spiders start making that final web, their little spider brains are being flooded with ecdysteroids, which is the hormone that the spider naturally releases when it’s ready to build a molting web. And scientists aren’t sure yet: Is the larvae actually producing the ecdysteroids? Is it somehow triggering its production in the spider through another compound? That’s something that they’re still figuring out.

Why is it important to understand how this behavior manipulation works?

In a lot of ways, this is looking at sort of really big questions about how behavior works, which is something that scientists are still piecing together, on so many levels for all different types of organisms, because there are so many factors that shape behavior. Some of them are genetics; some of them are biochemical; some of them have to do with environments; some of them have to do with social relationships. So, this is one way of trying to understand behavior writ large. 

You mentioned that these insects suppress the immune systems of their hosts. Is there stuff that we could learn from that about how immune systems work in general?

Oh yeah. Looking at the immunosuppressive aspect of zombifiers is definitely something that is a huge area of interest, because that could inform the development of immunosuppressive drugs, which is something that is just something that would be hugely beneficial to people. 

Not that this should be all about what’s in it for me, but that is usually a consideration for scientific research: Could there potentially be applications for this that have medical applications? And so, there is not yet a direct line between any research into how zombifiers evade their host’s immune system and the development of some kind of pharmaceutical immunosuppressive. But that’s definitely something that is part of the mix when scientists are following that line of investigation.

I think about all the insects that invade homes, some of which are beneficial, some of which are less so. Could we potentially borrow from this to fight off pests?

Pest control is definitely one avenue that scientists have explored. Is there some way that we can take what we’re seeing these zombifiers do to insects and apply it to insects that we don’t like? 

So baculoviruses — which are these viruses that infect caterpillars and make them climb and then dissolve their bodies into goo — this is something that has been deployed as a strategy for pest control in China and in Europe, in the US, in Brazil. 

These types of viruses are an interesting alternative to traditional insecticides because they are very targeted. They’re less toxic to the environment. They’re not harmful to insects that are not their host species and they’re not toxic to people. But they’re also not as quick as I think the insecticides that people have gotten used to. And people like things to be quick and they like them to be absolute. 

So what seems like the best way is perhaps to incorporate this alongside insecticides, and use this along with other approaches, because there are a lot of benefits to just going full-on zombie warfare to get rid of our agricultural pests.

Could humans be zombified this way? Like, are we also susceptible to this?

Well, there are some types of pathogens that are known to manipulate behavior in mammals and indeed in humans too. So rabies, of course. There have been medical cases of rabies-infected humans that are thousands of years old with documentation of heightened aggression. So there is already a virus among us that can manipulate human behavior. 

And recently, there have been studies into Toxoplasma gondii, which is the pathogen that causes toxoplasmosis. Its definitive host is cats. It’s very entrenched amongst human populations. And in fact, many, many people, millions of people, carry Toxoplasma gondii, but it doesn’t cause any symptoms. It tends to be dangerous in people that are pregnant or in immunocompromised people. Most of the people who are carrying Toxoplasma gondii have no symptoms. 

However, there have been studies recently in the last 10, 15 years or so, that have looked at people who are carrying the parasite and have found that there does seem to be evidence of certain types of behavior: of being more risk-taking, of being bolder. And what’s interesting about it is that Toxoplasma gondii is known for manipulating behavior in rodents. And what it does is it makes them bolder and less afraid of cats. 

What?

Because Toxoplasma gondii needs to reproduce inside cats. So it infects rodents, and then to get back into a cat, it makes the rodent less afraid of and attracted to the smell of cat pee. And that brings the rodent closer to a cat than it would normally go. And then once it’s eaten, then the parasite is back inside the cat. 

And scientists have found that this is true for other animals too. So hyena cubs that are infected with Toxoplasma gondii are bolder around lions and are more likely to be eaten by lions. Chimpanzees that are infected with Toxoplasma gondii lose their fear of jaguars. And some studies found that people who are infected with Toxoplasma gondii are more likely to make risky business decisions or be bolder in traffic.

There’s still a lot of work to be done because obviously human behavior is its own form of complicated. But there is some evidence that seems to suggest that Toxoplasma gondii can shape human behavior, too.

What? 

Did I just blow your mind?

So there could literally at this moment be zombifiers within us shaping us in some way?

It’s entirely possible. There are so many things that make us who we are that shape how we behave. There are environmental factors; there are social factors. But, you know, there might also be zombifiers.

It sounds like something out of science fiction: In the late 1950s, the US Army carved a tiny “city” into the Greenland ice sheet, 800 miles from the North Pole. It had living facilities, and scientific labs, and working showers, all powered by one small nuclear reactor.

The research base was called “Camp Century,” a Cold War scientific project that helped researchers deepen their understanding of ice. As part of their efforts, they wound up drilling close to a mile down through the ice sheet to pull up an ice core: a series of long cylinders of ice that serve as a record of Earth’s history, with everything from atmospheric gases to volcanic fallout preserved in their tightly packed layers.

The ice from Camp Century has been thoroughly sampled and studied since it first came out of the ice sheet. It, along with the ice from many other ice cores, has taught us a lot about Earth’s climate going back tens of thousands of years — about how abruptly climate can change and the role that greenhouse gases play in warming. 

But the drillers at Camp Century brought up more than just ice. They also brought up several feet of sediment from beneath it. Except, as a geoscientist named Paul Bierman, who wrote a whole book about the ice and sediment from Camp Century, explains, these samples went largely understudied for decades, with just a handful of papers written about them.

“ I think the focus of the community was almost laser on the ice and not on the stuff beneath it,” he says. 

These sediments from underneath the ice were so undervalued, in fact, that they disappeared into some freezers in Denmark for years. Until, in 2017, some researchers found them again. And when scientists finally started to study these sediments in earnest, they discovered a bonanza of former lifeforms and a trove of information.  

On the most recent episode of Vox’s Unexplainable podcast, we explore these long-ignored sediments, and learn what they can teach us about our climate past — and future.

“It was like a battleground,” Drew Harvell remembers. “It was really horrible.”

She’s reflecting on a time in December 2013, on the coast of Washington state, when she went out at low tide and saw hundreds of sick, dying sea stars. “There were arms that had just fallen off the stars,” she says. “It was really like a bomb had gone off.”

The stars were suffering from something known as sea star wasting disease. It’s a sickness that sounds like something out of a horror movie: Stars can develop lesions in their bodies. Eventually, their arms can detach and crawl away from them before the stars disintegrate completely.  

Harvell is a longtime marine ecologist whose specialty is marine diseases. And she was out for this low tide in 2013 because a massive outbreak of this seastar wasting had started spreading up and down the West Coast — from Mexico to Alaska — ultimately affecting around 20 distinct species of sea stars and wiping out entire populations in droves. In the decade since, some species have been able to bounce back, but others, like the sunflower sea star, continue to struggle. In California, for example, sunflower stars have almost completely died out.

The question in 2013 was: What, exactly, was killing all these stars? While marine ecologists like Harvell could recognize the symptoms of seastar wasting, they weren’t actually sure what was causing the disease. From the very beginning, though, it was something they wanted to figure out. And so, soon after the outbreak started, they collected sea stars to see if they could find a pathogen or other cause responsible for the wasting. The hunt for the culprit of this terrible, mysterious disease was on. 

Unfortunately, it was not straightforward.  

“ When this disease outbreak happened, we knew quite little about what was normal [in sea stars],” says Alyssa Gehman, who is also a marine disease ecologist. She says that when researchers are trying to do similar work to chase down a pathogen in, say, humans, they have an enormous trove of information to draw on about what bacteria and viruses are common to the human body, and what might be unusual. Not so for sea stars. “ We maybe had a little bit of information, but absolutely not enough to be able to really tease that out easily.”

Also, Gehman says, there can be a lag before the disease expresses itself, so some stars have the pathogen that caused the disease, but don’t present with symptoms yet, making it harder for scientists to even distinguish between sick stars and healthy ones as they run their tests. 

So even though a research team identified a virus that they thought might be associated with the wasting disease as early as 2014, over time, it became clear that it was most likely not the culprit, but rather just a virus present in many sea stars. 

“The results were always confusing,” Harvell remembers.

In the decade since the initial mass outbreak, other researchers have proposed other theories, but none have brought them to a definitive answer either. And yet, it became increasingly clear that an answer was needed, because people started to realize just how important the sunflower stars they had lost really were. 

“ We actually learned a lot from losing so many of these animals at once,” Gehman says. 

Before the outbreak, she says, they’d known that sunflower stars — giant sea stars that can be the size of dinner plates, or even bike tires — were skillful hunters and voracious eaters. They even knew that many things on the seafloor would run away from them. Gehman remembers taking a class on invertebrates back in college, where she learned that if you put even just the arm of a sunflower star in a tank with scallops, “the tank would explode with scallops swimming everywhere trying to get away.” 

But all that fearsome hunting was, it seems, pretty key to ecosystem health. In many places, she says, “ after the sea sunflower stars were lost, the urchin populations exploded.” 

And so the die-off of the sunflower star and the explosion of urchins has been connected to the collapse of the Northern California kelp forests, a marine ecosystem that provides a home for a rich diversity of species. 

A cross-state, cross-organizational partnership between the Nature Conservancy and a variety of research institutions is working hard to breed sunflower seastars in captivity in the hopes that they can be reintroduced to the coast and reassume their role in their ecosystems. But as Harvell remembers, she and Gehman knew that no recovery project would be successful if they couldn’t find the cause of sea star wasting disease.

“You’re not gonna be able to get these stars back in nature if you don’t know what’s killing them,” she says. 

So in 2021, as part of the larger partnership, Harvell and Gehman, along with a number of their colleagues, launched into an epidemiological detective project. Their quest: to finally pin down the cause of seastar wasting disease. 

“Really the work over the four years was done in the trenches by Dr. Melanie Prentice and Dr. Alyssa Gehman,” Harvell says, “and then one of my students, Grace Crandall.”

It was an emotionally difficult project because it required Gehman and her colleagues to deliberately infect many stars with the disease. 

“It feels bad,” she admits, and they would be open about that in the lab, “but we also can remember that we’re doing this for the good of the whole species.” 

That work has paid off, though, and now, after four years of research, they’ve nailed their culprit in a paper out in Nature Ecology & Evolution today. 

What follows is a conversation with Drew Harvell, edited for clarity and length, about what she and her collaborators found, how marine ecologists do this kind of detective work, and what identifying the culprit could mean for the future health of seastars.

How did you start the journey to figure out what actually had happened?

Well, we chose to work with the sunflower star because we knew it was the most susceptible and therefore was going to give us the most clear-cut results.  So we set up at Marrowstone Point, which was the USGS Fisheries virus lab [in Washington state], because that would give us the proper quarantine conditions and lots of running seawater.

The proper quarantine conditions — what does that mean?

All of the outflow water has to be cleansed of any potential virus or bacterium, and so all of the water has to be run through virus filters and also actually bleached in the end, so that we’re sure that nothing could get out. 

We did not want to do this work at our lab, Friday Harbor Labs, or at any of the Hakai labs in Canada because we were really worried that if we were holding animals with an infectious agent in our tanks without really stringent quarantine protocols, that we could be contributing to the outbreak.

So you have these sea stars. They’re in this quarantined environment. What is the methodology here? What are you doing to them or with them?

 So the question is: Is there something in a diseased star that’s making a healthy star sick? And that’s like the most important thing to demonstrate right from the beginning — that it is somehow transmissible. 

And so Melanie and Alyssa early on showed that even water that washed over a sick star would make healthy stars sick, and if you co-house them in the same aquarium, the healthy ones would always get sick when they were anywhere near or exposed to the water from a diseased star.

There’s something in the water.

That’s right. There’s something in the water. But they wanted to refine it a little bit more and know that it was something directly from the diseased star. And so they created a slurry from the tissues of the disease star and injected that into the healthy star to be able to show that there really was something infectious from the disease star that was making the healthy star sick and then die.

And then you control those kinds of what we call “challenge experiments” by inactivating in some way that slurry of infected disease stuff. And in this case, what they were able to do was to “heat-kill” [any pathogens in this slurry] by heating it up. And so the thing that was very successful right from the beginning was that the stars that were infected with a presumptive disease got sick and died, and the controls essentially stayed healthy.

You do that control to make sure that it’s not like…injecting a slurry into a star is what makes them sick?

That’s right. And you’re also having animals come in sick, right? So you want to know that they weren’t just gonna get sick anyway. You want to be sure that it was what you did that actually affected their health status. 

So you have a slurry — like a milkshake of sea star — and you know that within it is a problematic agent of some kind. How do you figure out what is in that milkshake that is the problem?

The real breakthrough came when Alyssa had the idea that maybe we should try a cleaner infection source and decided to test the coelomic fluid, which is basically the blood of the star. With a syringe, you can extract the coelomic fluid of the sick star and you can also heat-kill it, and you can do the same experiment challenging with that. And it was a really exciting moment because she and Melanie confirmed that that was a really effective way of transmitting the disease because it’s cleaner.

It’s cleaner, like there’s less stuff than in the tissue? Like blood is just like a simpler material?

Right. So, that was really the beginning of being able to figure out what it was that was in the coelomic fluid that was causing the disease. 

So basically it’s like: We’re gonna look in every sample in this fluid. There’s gonna be sort of an ingredient list. And in the first one, there’s ingredients ABC. In the second one, there’s ingredients BDF. And in the third one, there’s ingredients BYZ… So it seems like it might be ingredient B that’s causing the problem here because it’s consistent across all samples? 

Yeah, that’s exactly it. And so then that was very, very incredibly exciting. Wow. There’s this one bacterium — Vibrio pectenicida — that’s showing up in all of the diseased material samples. Could it be that?

We weren’t sure. We sort of thought, after 12 years, this is gonna be something so strange! So weird! You know, something alien that we’ve never seen before. And so to have a Vibrio — something that we think of as a little bit more common — turn up was really surprising.

Then one of our colleagues at the University of British Columbia, Amy Chan, was able to culture that particular bacterium from the disease star. And so now she had a pure culture of the presumptive killer. And then last summer, Melanie and Alyssa were able to test that again under quarantine conditions and find that it immediately killed the stars that were tested. 

How did you all feel?

Oh, we were definitely dancing around the room. It was — just such a happy moment of fulfillment. I really do like to say that at the beginning of the task that Nature Conservancy handed us — to figure out the causative agent — we told them again and again that this is a very risky project. We can’t guarantee we’re going to be successful.

So yeah, we were incredibly elated when we really felt confident in the answer. It was just hundreds and hundreds of hours of tests and challenge experiments that came out so beautifully.

What does it mean to finally have an answer here? What are the next steps?

This was the part of it that really kept me awake at night because I just felt so worried early on at the idea that we were working on a roadmap to recovery of a species without knowing what was killing it, and I just felt like we couldn’t do it if we were flying blind like that. 

We wouldn’t know what season the pathogenic agent came around. We wouldn’t know what its environmental reservoirs were. We didn’t know what was making stars susceptible. It was going to be really hard, and it wasn’t going to feel right to just put animals out in the wild without knowing more. 

And so knowing that this is one of the primary causative agents — maybe the only causative agent — allows us to test for it in the water. It allows us to find out if there are some bays where this is being concentrated, to find out if there are some foods the stars are eating that are concentrating this bacterium and delivering a lethal dose to a star. 

Now we’ll be able to answer those questions, and I think that’s going to give us a really good opportunity to design better strategies for saving them.

It feels like you now have a key to use to sort of unlock various pieces of this.

We totally do. And it’s so exciting and so gratifying because that’s what we’re supposed to do, right? As scientists and as disease ecologists, we’re supposed to solve these mysteries. And it feels really great to have solved this one. And I don’t think there’s a day in the last 12 years that I haven’t thought about it and been really frustrated we didn’t know what it was. So it’s particularly gratifying to me to have to have reached this point.

Drew Harvell is the author of many popular science books about marine biology and ecology, including her latest, The Ocean’s Menagerie. She also wrote a book about marine disease called Ocean Outbreak.

This story was originally published in The Highlight, Vox’s member-exclusive magazine. To get early access to member-exclusive stories every month, join the Vox Membership program today.

In just a few hours, the world I’m walking into will disappear beneath the waves. 

I’m at Pillar Point Harbor, a 40-minute drive from San Francisco, near low tide. And because this is one of the lowest tides this August, the water has drawn back like a curtain to expose an ecosystem that’s normally hidden away — a place called the rocky intertidal, or, because the receding water leaves little pools behind in the rocks, “the tidepools.”

Dawn has just broken, pods of pelicans fly overhead, and sea lions bark from the nearby harbor. But I’m more focused on following my guide, a zoologist named Rebecca Johnson, as she picks her way out into these seaweed-covered rocks, pointing out species as she goes. These smooth green strands are surfgrass. Those fat bladders of air that look kind of like puffed-up gloves are called “seasack.” This dark brown frond Johnson is draping over her shoulders is the aptly named “feather boa kelp.” 

“ They’re like wildflowers,” Johnson says, “But it’s seaweed.”

As we make our way deeper, she points out odd creatures that only the ocean could dream up. A boring clam (which is far from boring, but does bore into rock) puffs itself up like a fierce fleshy ball before squirting a jet of water directly into the air to fend off our threatening vibes. A pale white brittle star, like a flexible daddy longlegs, dances for us across some algae. And rows of fat green anemones wear bits of shells like tiny hats. 

“ The theory is that…they’re protecting themselves from the sun, like a sunscreen,” Johnson tells me.

We crouch together at the edge of a deep pool and see first one, then two — then three, four, five, six! — species of nudibranchs, the sea slugs that Johnson specializes in. One is hot pink and spiky. Another is an aggressive shade of orange. There’s a pale lemon one, a ghostly white one. Johnson even finds one covered in orange polka dots, like a marine clown. Some of these species, she tells me, bubbling with enthusiasm, eat anemones and steal their stinging cells, repurposing them as their own defenses.

This kind of diversity is wild to witness, but it isn’t unusual for these tidepools. 

“It’s one of the places in the world that you can see species of invertebrates all really, really concentrated,” Johnson told me.

We wander farther out, exploring this alien landscape together, until the tide begins to come back in and cover it over, bit by bit, hiding this weird world away again in a slow disappearing act.

“ It’s extra magical that you can only see it at certain times,” Johnson told me before we came out here. “You get this little peek, this little window. And that’s one of the things I love the most about it.”

Johnson has been coming to this exact spot off Pillar Point for almost three decades now, and in her role as director for the Center for Biodiversity and Community Science for the California Academy of Sciences, she spends time with volunteers monitoring tidepools up and down the California coasts. But she’s still enchanted with them. 

I’m not surprised. I fell in love with tidepools myself 20 years ago, when I first got to explore them as a kid at a summer camp in Mendocino. The odd, colorful creatures in them made me feel like magic was a little bit real, that science could feel like fantasy. It’s part of the reason I’m a science reporter today. 

But Johnson is worried about the future of these tidepools she loves so much. She’s worried that, like so many ecosystems around the world, they may be heading toward a much more dramatic, much more permanent disappearing act. 

So she, along with many, many collaborators all across the state of California and beyond, is doing what many scientists are trying to do for the ecosystems they study: to figure out — first, what’s actually happening to them, and second, what, if anything, we can do to save them. 

How did we get here? 

For Rebecca Johnson, the troubles really began around the arrival of “The Blob”: a marine heatwave. By 2014, it had warmed waters significantly along the West Coast of the United States. Johnson was hearing concerning things from participants in the programs she organized through Cal Academy to get people to go into the tidepools and make observations.

“They started seeing an increase in this really beautiful pink nudibranch called the Hopkins Rose nudibranch,” she says. 

Historically, the Hopkins Rose nudibranch has lived in Southern California — and ventured up to Johnson’s more northern tidepools mostly during El Niño years. But as the temperatures shifted for the Blob, the spiky pink balls were showing up in huge numbers.

“It became the most common thing,” Johnson remembers. 

She was also hearing disturbing reports about another animal — the sea star, known more colloquially as the starfish.

As early as 2013, before The Blob really hit, divers and researchers had started noticing that sea stars were, quite literally, wasting away. 

“They were seeing white lesions on starfishes. And they were seeing the starfish kind of disintegrate in front of them,” she says. “[They would] see it one day with these lesions. They’d come back the next day and it was like almost dissolved and then almost gone.” 

Sea star wasting also isn’t unheard of, but in this instance, the wasting hit species after species of sea stars — at least 20 species in all. Also, as an evolutionary ecologist who studied this outbreak, Lauren Schiebelhut, told me, wasting normally happens on a more local scale — isolated to a single bay, for example.

“For it to spread across the entire West Coast here, that was something we had not seen before,” Schiebelhut says. 

Scientists have been trying to work out what caused this massive shift for over a decade. Some theorized that it was a virus, and people have investigated the possibility of a bacterial issue. One researcher told me that her team is close to publishing a paper that should provide some more answers about an infectious agent here. But whatever the exact cause — and even though the wasting started before The Blob set in — scientists studying one species of sea star found that the biggest declines coincided with the warmer temperatures. Huge numbers of sea stars wasted away — with some locations losing over 90 percent of their stars. 

The Blob “certainly seemed to exacerbate it,” Schiebelhut says.

At one point, Johnson went down to her favorite tidepooling spot, Pillar Point, with a colleague, just to “see what they could see,” and they saw almost no sea stars. 

“It was just like the most bizarre feeling,” she says. “I was still at this place that was spectacularly beautiful, covered with algae. All these other invertebrates are there. But there’s just something kind of off about it.”

She says it was like going into your room, only to realize that someone has moved all your stuff very slightly. 

“And you’re like, ‘What’s wrong with this room?’ It had that disconcerting, unsettling feeling.”

This place Johnson knew so well — had been documenting and sharing with people for decades — suddenly felt unfamiliar. And at that moment, she felt a deep, deep uncertainty about its future. 

“Like, there might not be starfish, like ever,” she remembers thinking, “What does that mean?”

What it would mean to lose so many sea stars

The reason that Johnson was so worried about sea stars was not just that the tidepools at Pillar Point looked different. She was worried about the role sea stars play in the tidepools ecosystem. To us, they might seem like pretty creatures that come in a fun shape, but to many of the ocean animals they interact with, they are voracious predators that help keep their ecosystems in balance — chowing down on everything from mussels and barnacles to snails.  

To understand why this is so important, let’s journey a little beyond the tidepools, a little farther offshore, into the California kelp forests. These are underwater forests of algae that are home to a huge diversity of animals, from fish and octopi to abalone. Kelp forests also provide a buffer for the coast against erosion, and they absorb and store large amounts of carbon dioxide, which benefits all of us as we try to stave off climate change. So they’re amazing ecosystems.

But, like any forest, California’s coastal kelp forest has grazers — basically the marine equivalent of deer. In this case, these are animals like the purple sea urchin, a spiky purple pincushion that chows down enthusiastically on kelp. 

Normally, Peter Roopnarine, a paleontologist at the California Academy of Sciences who has studied kelp forests tells me, sea urchins are content to eat the bits of detritus that the kelp shed naturally. But if there isn’t enough kelp detritus to go around, urchins can start feeding on the living kelp itself. 

“ That will happen if, for example, there are not enough predators around to keep their population in control, to keep them hiding,” Roopnarine says. “ Pretty soon they kill the kelp, and what you’re left with is what we call an urchin barren, which are these stretches of seafloor that are covered with urchins. And nothing else.” 

Sea otters are one of the predators — one of the wolves, to continue the metaphor, to our urchin deer — keeping urchins in check along some parts of the coast. Sea otters were hunted aggressively by European settlers, and have not returned along the northern part of the coast, but have made a comeback in central California.  

Another important wolf for these kelp forests, though, is a sea star known as pycnopodia helianthoides, or the “sunflower sea star.” Sunflower sea stars are beautiful, often purple or pink, and kind of squishy. But they are also, at least as sea stars go, big. They can have 20 arms, and grow to the size of a dinner plate or larger. (As a kid, when we found them in the tidepools, we used to have to hold them in two hands.) And researchers have increasingly found that they, too, did a lot of work to keep urchins in check.  

This is why it was such a big deal when the sea star wasting syndrome hit and wiped out so many sea stars, sunflower sea stars very much included. 

After the sickness, a lot of sea star species did start to come back. You can find sea stars like ochre stars, leather stars, and bat stars in California tidepools, for example. But while sunflower sea stars can still be found in the wild further north, in places like Washington state, they have not bounced back along the coast of California. And that, scientists suggest, may have contributed to the issues they’re now seeing in kelp forests. 

Satellite surveys from a few years ago showed that the kelp forests off of Northern California have shrunk by 95 percent. Once again, this is probably due to a combination of factors. High water temperatures may have weakened the kelp, for example. But another factor was the explosion of urchin populations. 

“This lack of the sunflower star in the kelp forest, especially in Northern California,” Johnson says, “led to the increase of urchins. And the urchins then ate all the kelp.”

What does this mean for the future of these tidepools? 

The tidepools haven’t been hit as hard as the kelp forests. Clearly, as our visit in August showed, a place like Pillar Point has not turned into the equivalent of an urchin barren and is instead still home to a diversity of creatures.  

Still, Johnson says, they have been affected. She has, anecdotally, noticed grazing species like abalone that normally spend more of their time in the kelp forests moving over to tidepools, probably in search of kelp to eat. And as temperatures continue warming over time, tidepool ecosystems are changing in other ways. A recent paper showed that a species of nudibranch range has moved northward. Another study showed that a whole bunch of different marine species, including nudibranchs, but also species of snail, lobster, and crab were spotted farther north than their usual range during a heat wave. Some of these species are predators that might shake up the dynamics and the ecosystems they’re coming into. 

“We don’t actually know what happens when they move north,” Johnson says. “ We don’t really know the impact.” 

And then, as Schiebelhut, the geneticist who studies sea stars, told me, there are other stressors like pollution and runoff from wildfires. In January, more than 57,000 acres burned from a series of wildfires in Greater Los Angeles — a disaster whose scope of damage on intertidal ecosystems is not yet clear, researchers told me.

 “The disturbances are becoming more frequent, more intense,” Schiebelhut says. “It is a challenge to the system.” 

Johnson admits that it’s hard to know exactly how to interpret all these changes and stressors and use them to predict the future of the tidepools. After all, the California coastal ecosystems have survived the loss of important species before, and survived big natural disasters too. 

So I turned to Roopnarine, the paleontologist. He studies how ancient ecosystems weathered — or didn’t weather — things like climate change, and what we might learn from them to apply to ecosystems facing challenges today. I hoped he would have a sense of how the current moment fits into the bigger patterns of history. 

“If you look in the fossil record,” he told me, “one of the things that’s really remarkable is that ecosystems can last a very long time. Millions of years. Species will come and go in those ecosystems, but what they do, who they do it to, and so on? That doesn’t change.”

Ecosystems are a little like, say, a baseball team. You’ll always need certain players in certain roles — pitchers and catchers and shortstops and outfielders. Different players can retire and be replaced by other players — if one predator disappears, another predator might be able to take over some of the role that it plays, for example. 

But Roopnarine’s research into the fossil record also shows that no ecosystem baseball team is endlessly flexible.

“They do eventually come to an end,” he says. Usually, that’s when really extreme changes occur. And when he looks at the moments in the past when the climate changed dramatically, and he looks at forecasts for our future, he’s very worried. 

“We have to be realistic that if we do nothing, the future is extremely grim,” he tells me, “There is no sugarcoating it.”

What can we do? 

When it comes to safeguarding the future health of California’s coastal ecosystems, there are lots of people doing lots of things.

Johnson is working with colleagues on a system that uses the community science app iNaturalist to better monitor the health of coastal tidepools. 

Anyone who goes to the tide pools can upload photos of all the species that they see. Those photos, geotagged with locations and timestamps, will hopefully help researchers figure out how populations are changing, to model the future of this ecosystem. They could also potentially serve as a warning system if there are big die-offs again, so scientists can try and intervene earlier. 

Schiebelhut has studied the genomes of sea stars that did recover, to see what can be learned about what made them so resilient to wasting. 

The California state government has partnered with nonprofits and commercial fishermen to clear urchins and restore kelp. 

And then there’s the consortium of institutions up and down the coast, all working on an initiative to try to breed sunflower sea stars in captivity so that they might, eventually, be released back into the wild and resume their role as key predators.

“ There is no one person that can do all the things,” says Ashley Kidd, a project manager at the Sunflower Star Lab, one of the many groups working together to bring sunflower sea stars back. What gives her hope is that so many different people, from so many institutions, are working together toward solutions. 

“ You can’t have all the knowledge of disease ecology, behavioral ecology, aquaculture by yourself,” Kidd says. “It is a much bigger, wonderful group of people that you get to work with and then be connected with. … You’re not alone.”

When I first heard that these tidepools might be in trouble, I felt an overwhelming sense of loss. 

This ecosystem made me believe that the real world had its own magic — because sure, fairies might not be real, but opalescent nudibranchs come pretty close. It hurts to think that that magic might dim, or even disappear. But walking through these pools with Johnson and watching her walk over to a mother and her daughter to show them nudibranchs, eagerly sharing this world with strangers, I felt delight, and a wonderful sense of present-ness. I felt part of that community. A sense that, whatever the future of these tidepools might look like, they were here, now, and as magical as ever. 

“In the midst of climate change and a future that is going to be hotter and harder and more difficult for people, you have to have joy,” Johnson says. “I struggle with it. I feel like marine systems especially are pretty complicated to think about restoring. What do you actually do out here? How do you protect things?…But you can’t stop doing it, because then you’ve kind of lost everything.”