Kelp by Mendel Skulski
Summary
How did nuclear testing accidentally reshape our understanding of food webs and marine ecology? Why did sea otters bounce back from near-extinction on some parts of the Pacific coast, but are still absent in others? We speak with Dr. Jim Estes (a godfather of the field) about a series of serendipitous events that led to the re-writing of textbook ecology.
This is part one of our three-part series on kelp worlds. Click here for part two.
Show Notes
This episode features Dr. James Estes, as well as the research of Terrie Williams, John Palmisano, Tim Tinker, Dave Duggins, Jane Watson, Bob Paine, Dan Doak, and many many others. Dr. Estes is author of Serendipity: An Ecologist's Quest to Understand Nature.
Music in this episode was produced by Ben Hamilton, Leucrocuta, Tidebringer, and Sunfish Moon Light.
This episode was produced by Adam Huggins and Mendel Skulski, with help from Simone Miller
Special thanks to Anne Salomon.
This podcast includes audio recorded by Stefan021, flood-mix, GowlerMusic, Ottomaani138, RutgerMuller, eggsandwhichent, theMfish, Macif, and jnomix, protected by Creative Commons attribution licenses, and accessed through the Freesound Project. This podcast also contains music from the Project Gutenberg Library. It also incorporates a number of declassified film reels from the now-defunct U.S. Atomic Energy Commission.
A lot of research goes into each episode of Future Ecologies, and we like to cite our sources. Note: the literature on this subject is vast. Below is a selection of papers and books most immediately relevant to this episode:
Burt, J. M., Tinker, M. T., Okamoto, D. K., Demes, K. W., Holmes, K., & Salomon, A. K. (2018). Sudden collapse of a mesopredator reveals its complementary role in mediating rocky reef regime shifts. Proceedings of the Royal Society B: Biological Sciences, 285(1883), 20180553.
Duggins, D. O. (1980). Kelp Beds and Sea Otters: An Experimental Approach. Ecology, 61(3), 447–453.
Estes, J. A., & Palmisano, J. F. (1974). Sea Otters: Their Role in Structuring Nearshore Communities. Science, 185(4156), 1058–1060.
Estes, J. A., Duggins, D. O., & Rathbun, G. B. (1989). The Ecology of Extinctions in Kelp Forest Communities. Conservation Biology, 3(3), 252–264.
Estes, J. A., Tinker, M. T., Williams, T. M., & Doak, D. F. (1998). Killer Whale Predation on Sea Otters Linking Oceanic and Nearshore Ecosystems. Science, 282(5388), 473–476.
Estes, J., Doak, D., Springer, A., & Williams, T. (2009). Causes and consequences of marine mammal population declines in southwest Alaska: a food-web perspective. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1524), 1647–1658.
Estes, J. A., et al. (2011). Trophic Downgrading of Planet Earth. Science, 333(6040), 301–306.
Estes, J. A. (2016). Serendipity: an ecologist’s quest to understand nature. Oakland, CA: University of California Press.
Filbee-Dexter, K., & Scheibling, R. (2014). Sea urchin barrens as alternative stable states of collapsed kelp ecosystems. Marine Ecology Progress Series, 495, 1–25.
Fisher, J. T., Pasztor, C., Wilson, A., Volpe, J. P., & Anholt, B. R. (2014). Recolonizing sea otters spatially segregate from pinnipeds on the Canadian Pacific coastline: The implications of segregation for species conservation. Biological Conservation, 177, 148–155.
Harvell, C. D., Montecino-Latorre, D., Caldwell, J. M., Burt, J. M., Bosley, K., Keller, A., … Gaydos, J. K. (2019). Disease epidemic and a marine heat wave are associated with the continental-scale collapse of a pivotal predator (Pycnopodia helianthoides). Science Advances, 5(1).
Konar, B., & Estes, J. A. (2003). The Stability Of Boundary Regions Between Kelp Beds And Deforested Areas. Ecology, 84(1), 174–185.
Kuker, K., & Barrett-Lennard, L. (2010). A re-evaluation of the role of killer whales Orcinus orca in a population decline of sea otters Enhydra lutris in the Aleutian Islands and a review of alternative hypotheses. Mammal Review, 40(2), 103–124.
McLeish, T. (2018). Return of the sea otter the story of the animal that evaded extinction on the Pacific Coast. Seattle: Sasquatch Books.
Paine, R. T. (1966). Food Web Complexity and Species Diversity. The American Naturalist, 100(910), 65–75.
Paine, R. T. (1969). The Pisaster-Tegula Interaction: Prey Patches, Predator Food Preference, and Intertidal Community Structure. Ecology, 50(6), 950–961.
Smale, D. A. (2019). Impacts of ocean warming on kelp forest ecosystems. New Phytologist.
Springer, A. M., Estes, J. A., Vliet, G. B. V., Williams, T. M., Doak, D. F., Danner, E. M., … Pfister, B. (2003). Sequential megafaunal collapse in the North Pacific Ocean: An ongoing legacy of industrial whaling? Proceedings of the National Academy of Sciences, 100(21), 12223–12228.
Stewart, N. L., Konar, B., & Tinker, M. T. (2014). Testing the nutritional-limitation, predator-avoidance, and storm-avoidance hypotheses for restricted sea otter habitat use in the Aleutian Islands, Alaska. Oecologia, 177(3), 645–655.
Trites, A. W., Deecke, V. B., Gregr, E. J., Ford, J. K., & Olesiuk, P. F. (2007). Killer Whales, Whaling, And Sequential Megafaunal Collapse In The North Pacific: A Comparative Analysis Of The Dynamics Of Marine Mammals In Alaska And British Columbia Following Commercial Whaling. Marine Mammal Science, 23(4), 751–765.
Wade, P. R., Hoef, J. M. V., & Demaster, D. P. (2009). Mammal-eating killer whales and their prey-trend data for pinnipeds and sea otters in the North Pacific Ocean do not support the sequential megafaunal collapse hypothesis. Marine Mammal Science, 25(3), 737–747.
Watson, J., & Estes, J. A. (2011). Stability, resilience, and phase shifts in rocky subtidal communities along the west coast of Vancouver Island, Canada. Ecological Monographs, 81(2), 215–239.
Williams, T. M., Estes, J. A., Doak, D. F., & Springer, A. M. (2004). Killer Appetites: Assessing The Role Of Predators In Ecological Communities. Ecology, 85(12), 3373–3384.
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Transcript
Introduction Voiceover 00:01
You are listening to Season Two of Future Ecologies.
[Suspenseful old-timey music]
Media Clip 00:14
[Archival Narrator 1] The Milrow Event took place in Alaska on the island of Amchitka. Amchitka was under consideration as a supplemental site for the testing of high-yield atomic devices. Alaska is a big state. This way, we can see just how big.
Adam Huggins 00:33
At the height of the Cold War between 1965 in 1971, the Atomic Energy Commission detonated three nuclear warheads underground on Amchitka Island in the middle of the Bering Sea, halfway between Alaska and the USSR.
Media Clip 00:50
[Archival Narrator 1] After World War Two, Amchitka was largely forgotten. 160 square miles of barren tundra, bearing the scars and decaying installations left by the thousands of American G.I.s who served here during the war years. Then, Long Shot reawakened the island.
Adam Huggins 01:11
After decades of testing in the Nevada desert, Amchitka gave the AEC (unclear) a new lease on life. First Long Shot, and then Milrow, a one megaton bomb detonated at 4000 feet below the surface.
[Explosion sound]
Adam Huggins 01:29
And that's when an unlikely figure enters the picture, almost entirely by chance.
Jim Estes 01:35
I finished my master's degree in 1969. So that was during the Vietnam War, and I thought I was going to probably get inducted and have to go into the army. But I feel the physical exam, I was just a fluke. And, uh, so I failed the exam. And there I was, and one of my professors at Washington State where I got my master's degree, was a consultant with the Atomic Energy Commission at the time.
Adam Huggins 02:04
This is Dr. Jim Estes.
Jim Estes 02:07
And I'm retired now, Emeritus faculty here at UC Santa Cruz and I worked for the federal government as a research scientist for most of my career and then here for the last 15 years or so.
[Mysterious music]
Media Clip 02:22
[Archival Narrator 1] The purpose of the Milrow Event was to test an island, not a weapon design. Good contained underground nuclear test would be conducted with no hazard to off-island people and within the constraints of the limited Nuclear Test Ban Treaty. Could these activities be conducted without a serious adverse impact on the wildlife of the island?
[Music fades out]
Jim Estes 02:53
They had really not taken seriously the growing political and public concern over environmental assessment. And so when they did, they decided to go out to Amchitka. Island. They went out with a very different mindset.
Adam Huggins 03:07
Jim's contact at the AEC was a professor by the name of Vincent Schultz.
Jim Estes 03:11
He was a statistical ecologist and we'd become very good friends and he called me up and said the AEC is looking for somebody to go out to Amchitka Island and work on sea otters. Are you interested? Yeah.
Media Clip 03:26
[Archival Narrator 1] It's good to relax after a busy day. An average day. But a busy day. These fellows wearing the warm coats, spend a good part of each day just searching for food. And then the sea, at this point in time, it's becoming difficult to find enough food to go around. But things are looking up, as you will see.
Jim Estes 03:40
I was brought in mostly because the people who had been working on sea otters before, they had not been happy with their work. I had no training at all in any of it before, but they wanted someone that would go out for a couple of years and spend time sort of becoming intimate with a system and with a species. And so that's how I got into it.
Adam Huggins 04:16
Jim's assignment was strategic. Well, it's amusing to listen to these old propaganda reels. There's a reason why the AEC was making films about sea otters, and flying young scientists up to study them. After the fallout from the Milrow Test, they were facing very real pressure, at home and abroad, to discontinue testing on Amchitka or anywhere really. And they needed to convince the public that their activities were safe and beneficial to society. Especially since they were gearing up for their biggest test yet
Media Clip 04:45
[Archival Narrator 1] In the late summer of 1971, final preparations were being made on Amchitka Island in the remote Aleutian island chain of Alaska for Project Cannikin.
Adam Huggins 04:59
Thousands of environmental activists stormed the Trans-Boundary Peach Arch in British Columbia, in opposition to Cannikin, forming a coalition that would eventually result in the maiden voyage of a newly named organization called Greenpeace.
Media Clip 05:11
[Archival Narrator 2] Brothers and sisters in Greenpeace. You are supporting the first Greenpeace project, sending a ship to Amchitka to try to stop the testing of hydrogen bombs there or anywhere.
Adam Huggins 05:30
This was the context in which a young Jim Estes, still wet behind the ears, caught a flight to Amchitka Island, sight unseen, to study sea otters. And though, a few short years after the detonation, the Atomic Energy Commission would be shuttered for good Jim Estes would return again and again to the Aleutian archipelago for the rest of his career. What he discovered there would change the field of ecology forever, popularizing now familiar concepts like keystone species and reframing the relationships between predators, prey, and their ecosystems. This month and next, on Future Ecologies, we're diving into the cold, nutrient-rich waters of the Northern Pacific Coast, to lose ourselves alongside sea otters in their kelp worlds. From Baja to Kamchatka, kelp forests form a green belt that ties us all to one another, to our past, present and future ecologies. Today, we talked to Jim Estes as part one of a three-part series. This episode is called Trophic Cascadia.
Introduction Voiceover 06:40
Broadcasting from the unceded, shared, and asserted territory of the Penelakut, Hwlitsum, and other Hul’qumi’num speaking peoples, this if Future Ecologies, where your hosts - Adam Huggins, and Mendel Skulski - explore the shape of our world, through ecology, design, and sound.
[Woodwind music]
Adam Huggins 07:36
Hey, Mendel.
Mendel Skulski 07:37
Hey, Adam, what's up?
Adam Huggins 07:39
Um, what do you know about the Aleutian Islands?
Mendel Skulski 07:43
They're like the... like... if Alaska melted while rocketing eastward... they're the little drips that fell off the western tip.
Adam Huggins 07:56
[Laughs] That's actually a really good description.
Mendel Skulski 07:59
Thanks
Jim Estes 08:00
So the Aleutian Islands are really the volcanic product of the North Pacific Plate subduction zone. So the North Pacific Plate is moving northward, it's diving underneath whereever the plate sits above it, and that creates this very thin layer of crust and volcanism and that volcanism is what generated the Aleutian Islands. It's a sub-Arctic environment, treeless, cool, but not bitter cold. It's very maritime. And so it's a very stormy place. You know, my initial impression was... it was daunting to land there for the first time and see this vast, treeless area. You know, I suppose my impression was on the one hand, it was exciting. On the other hand, it was frightening.
Mendel Skulski 08:53
I for one, would feel no small amount of trepidation if I had to show up for work at a nuclear testing zone, just outside the Arctic Circle.
Adam Huggins 09:05
Yeah, but I mean, sea otters, Mendel, sea otters. How – how could you resist? How could anyone resist sea otters?
Mendel Skulski 09:13
Yeah, they are. They are cute.
Adam Huggins 09:14
And to explain the draw of working on sea otters at the time, I've got one more Atomic Energy Commission film reel for you.
Mendel Skulski 09:21
Oh, nice.
Adam Huggins 09:22
Now Amchitka Island is part of the Alaska Maritime National Wildlife Refuge. And despite its history of military occupation, it's also teeming with life.
[Orchestral music]
Media Clip 09:31
[Archival Narrator 1] But most unique of all inhabitants in the frigid waters around these cheerless fog-bound islands, the sea otter. An aquatic mammal, ungainly and almost helpless ashore, in the sea, he has grace... and style. Bristling silver whiskers make him seem serious and wise. Fact is, he is shy and suspicious. Time was when sea otters, numerous as flocks of birds, swam and fished the coastal waters of America, from the outer tip of the Aleutians on down into Mexico. But that was long ago. Perhaps the world's most luxurious fur, fine, dense and very valuable. Almost two centuries of hunters had roamed the seas, decimating sea otter colonies. And by the turn of the 20th century, these pleasant playful creatures were on the verge of extinction.
Adam Huggins 10:35
And they had only really survived in a couple of small populations in a couple of places. And one of those places was Amchitka and the other nearby islands. In between 1911, when the treaty that protected sea otters was signed and the late 1960s, that population had grown from just a handful of individuals to thousands of sea otters. But you know, sea otters are cute and cuddly, and people tend to be concerned about things that are cute and cuddly.
Mendel Skulski 11:09
Naturally.
Adam Huggins 11:09
So the idea of... they had this beautiful remote island where they could set nuclear bombs off underground. Unfortunately, it's surrounded by the cutest and cuddliest creatures on the planet.
Mendel Skulski 11:20
The most effective protesters imaginable.
Adam Huggins 11:23
Exactly. Hence, they recorded some really wild footage like this, showing that, after the nuclear blast...
Media Clip 11:30
[Archival Narrator 1] Scientists found the sea otters swimming in their cages, eagerly awaiting their next meal, a frozen sole.
Mendel Skulski 11:37
Wow.
Adam Huggins 11:38
Yeah. The military is mainly concerned with the question of: how did setting up a nuclear bomb underground affect sea otters?
Mendel Skulski 11:44
Yeah, just the kind of practical scientific question we all ask ourselves from time to time.
Adam Huggins 11:52
Yeah. So Jim gets to work preparing for Cannikin.
Jim Estes 11:56
I work there fairly intensively for two years.
Adam Huggins 12:00
When the test finally occurs, a ton of sea otters die, and Jim makes an estimate of the damage, leading to this incredible New York Times headline: '900 otter deaths tied to Atomic Energy Commission test'.
Mendel Skulski 12:12
Ugh.
Adam Huggins 12:13
But in the meantime, he's actually been working on his own questions. He's trying to figure out how the abundant kelp forests that the sea otters on Amchitka lived in, affected their behavior and morphology. But he hits a roadblock when his attempts to radio-collar sea otters fails. And that's when in the summer of 1971, a researcher named Bob Payne showed up on Amchitka. Now, Bob was an ecologist, and just a few short years previously, he had introduced the idea of a keystone species into the scientific literature.
Mendel Skulski 12:47
Oh, hey, I know this story. Uh... can I do this part?
Adam Huggins 12:51
Are you – are you going to explain a thing?
Mendel Skulski 12:53
Hell yeah. I'm gonna explain a thing. We're bringing it back.
[“Mendel Explains A Thing" theme]
Mendel Skulski 13:09
Okay, so back in the 60s, ecology mostly evolved around studying how ecosystems affected individual species and their fitness. Like, how plentiful is my food? And how does that affect me?
Adam Huggins 13:24
In ecology we call this a bottom-up approach.
Mendel Skulski 13:26
Hey, who's doing the explaining here?
Adam Huggins 13:28
Sorry.
Mendel Skulski 13:29
Yeah, better be. So, here comes Bob Payne, and he's studying these super diverse, super dynamic intertidal communities on the Olympic Peninsula in Washington State. But he's looking at something different. He's looking at how predators affect their ecosystems.
Adam Huggins 13:46
[Whispers] We call this a top-down approach.
Mendel Skulski 13:48
He's looking at starfish, specifically the beautiful purple and orange starfish that were common on this coast, before the sea star wasting disease hit. We'll – we'll touch on that later. And he has this hunch. So he does what sea star wasting disease will actually do half a century later, he removes all the starfish from part of the intertidal zone, taking care to leave another area untouched as a control.
[Sounds of water splashing]
Mendel Skulski 14:16
Then he sits back and watches what happens. And it turns out in the area where he removed starfish, species diversity starts to plummet. First, acorn barnacles start to expand and take up all the available real estate, crowding other species out. Later, California mussels take over. What's clear is that the starfish were effectively regulating the whole ecosystem, keeping each of its choice prey species in check. Even though there are relatively few starfish compared to all the other species, they play this critical, previously invisible role, to make this effect visible. He used the term "keystone species" , which is like a cool reference to the central stone in an arch. Without that stone, the whole structure collapses. Keystone species have this outsized impact on their ecosystem relative to their own numbers within it. This term has since been applied to beavers, elephants, famously the wolves of Yellowstone. But it all started with Bob Payne and the sea stars.
Adam Huggins 15:21
Thanks for explaining a thing.
Mendel Skulski 15:22
Yeah, you're welcome. It's been too long.
Adam Huggins 15:24
So, back to Jim. It's summer of 1971. And he doesn't know any of this yet. After all, this research is hot off the presses. But Bob Payne plays a pivotal role in his story.
Jim Estes 15:38
So I met Bob during that trip. And we spoke the night before he left and he asked me a little bit about what I was doing and I was kind of... didn't really know what I was doing [laughs]. And he simply asked me the question, did you ever think about looking at the system not from the perspective of how the system's affecting otters but from the perspective of how otters are affecting the system.
Adam Huggins 16:01
And this serendipitous conversation sets off a light in Jim's head. He writes in his book, which is called... uh... Serendipity, that before this conversation, he had been trying to develop very challenging methods to answer not very interesting questions. But suddenly he realized he could ask a very interesting question with the simplest method imaginable, which is just... direct comparison.
Jim Estes 16:24
I was very aware of something that he wasn't aware of. And that was the history of otters and the sort of the spatial and geographic history of otters across the Aleutians and the fact that they had simply not recovered at many of the islands but had recovered at quite a few others. So Amchitka, where I was working, they had recovered. 100 miles off, there were some other islands where they hadn't recovered, but they had been abundant. We knew that from the fur trade records. And the reason they hadn't recovered is because they're just not a very mobile species. They don't move around very much. And so some of these islands that where the populations had been exterminated, they had not recovered. It had been probably two hundred years since the otters had been there, and I thought, my gosh, what a – what an amazing natural experiment to go to some of these places where otters had once been, and simply look at it and see, is it any different from the places that they have recovered?
Adam Huggins 17:12
This long chain of similar islands with dissimilar human legacies presented a perfect test case for the question Jim wanted to ask. So he convinces the Atomic Energy Commission to send him 200 miles west to Shemya Island, where sea otters had been absent for over a century. After getting clearance with the local colonel, he doesn't waste any time. He puts on his wetsuit and dives right in.
[Sound of water splashing]
Jim Estes 17:39
And, you know, one instance of looking at that system, it became so obvious what they – that it was a big deal. As soon as I looked at the system at Shemya, I recognized how different it was from the system at Amchitka. You know, there was, there was no kelp and there were lots of urchins, and there were no otters and it just all felt you know, it fit together, that the otters were having a big effect. And I knew enough ecology at the time to know what was going on. I knew otters ate urchins, I knew urchins ate kelp. I would say that it happened in less than a millisecond. I mean, just an instant glance and it was clear what was going on. You know, it took another probably 10 or 20 years to convince a critical scientific community that we had all the processes, right, because it was just a comparison of two islands. It could have differed from any for all sorts of reasons.
Adam Huggins 18:35
I'll spare you the scientific due diligence that Jim undertook to prove the point. But the result is that Jim's work introduces the urchin-otter-kelp love triangle to the world, a triad that many of our listeners are likely familiar with, from the news or from ecology 101. But if you'll bear with me, I'd actually like to formally introduce these characters to help flesh out this underwater drama. Because this story is is about to get much more complex.
Mendel Skulski 19:01
Okay, let's do it.
Adam Huggins 19:03
So first we have kelp, beautiful languid, slimy kelp.
Mendel Skulski 19:08
Mmm.
Adam Huggins 19:09
Well, we refer to kelp ecosystems as forests. kelp aren't trees, or even what we commonly think of as plants. They're actually algae, specifically brown algae. They're distinct from green and red algae and considerably more complex morphologically, because they have this tough, claw-like appendage called a holdfast that anchors them to the seabed, followed by a stem-like stipe, which supports the blade... and a blade which comes in all sorts of shapes. Some kelps like bull kelp are annuals and they have inflatable gas bladders that hold them upright in the water column. Others like sugar kelp are perennial and just sway with the current. But taken together, kelp ecosystems are incredibly productive and provide food, shelter and habitat complexity that supports an incredible array of species.
Mendel Skulski 20:04
I can see you're getting a little carried away with the photosynthetic life. So, I'm just gonna butt in here and introduce urchins.
Adam Huggins 20:12
All right.
Mendel Skulski 20:17
Sea urchins are spiny, spherical echinoderms that come in a wide variety of sizes, colors, and if we're being honest, flavors. They've got this hard shell called a test with all the soft bits protected inside, including their reproductive organs, which, if you're a hungry human, or a sea otter, you can scrape out and eat. The test has a mouth, known as Aristotle's lantern at the south pole, and an anus –
Adam Huggins 20:46
– otherwise known as Plato's portal –
Mendel Skulski 20:48
– that that's not true. [laughs] That's at the north pole. Sea urchins basically roam the seabed, voraciously consuming all sorts of things, but especially algae and kelp. They have these five sharp teeth that are perfect for severing the blade and stipe of a kelp from its holdfast, setting the whole thing adrift. A herd of sea urchins can easily clear-cut and consume whole kelp forests. But thankfully, they happen to be the favorite food of...
Adam Huggins 21:19
Sea otters.
[Upbeat dance track plays]
Adam Huggins 21:20
And a raft of otters can effectively keep a sea urchin population in check. This is the major finding of Jim's early research in the Aleutians, that sea otters effectively create the kelp ecosystem they live in by controlling sea urchins.
[Music distorts]
Adam Huggins 21:35
Remove the otters and... the kelp begins to disappear, eventually resulting in an urchin barren which is exactly... what it sounds like. A desert-like seabed of urchins, coralline algae and not much else, as far as the eye can see. So Jim does a study to document this and write it all up, and it's published in the very renowned journal Science in 1974. This is basically textbook ecology now, but at the time, many in the scientific community were skeptical. At this point though, Jim's work with the AEC on Amchitka was over, and he wasn't sure that he would make it back up to the Aleutians.
Jim Estes 22:26
But in that in 1974, when I finished my degree, I was hired by the Fish and Wildlife Service to go back to Alaska and work for their research division.
Adam Huggins 22:34
So he establishes a long-term research program on another island, Attu, where sea otters have only recently recolonized, but haven't become numerous enough to seriously impact the urchin populations. And he goes there almost every year for the next two decades to document the system, expecting that it will transition from primarily urchin barren to primarily kelp forest as the sea otter population expands. That would be the prediction.
Mendel Skulski 23:03
That sounds a lot like the Marine Science equivalent of watching paint dry.
Adam Huggins 23:08
Science can be tedious, for sure. But for Jim, it was really important to make sure that he had it right. That being said, there is an opportunity cost to all of that rigor.
Jim Estes 23:21
We waste so much time not learning interesting things, but you know, trying to make sure we're not wrong about things that we're almost certainly not going to be wrong about.
[Music distorts and fades out]
Adam Huggins 23:36
So right now, since long term ecological research can be kind of dull, we're going to leave Jim on Attu Island for the moment, and take the opportunity to rewind a bit. Before Cannikin, before Milrow, and before even Long Shot. Before all these nuclear tests in the late 1960s. Remember, all those film reels I played you that the AEC produced about sea otters?
Mendel Skulski 24:00
How could I forget?
Adam Huggins 24:02
Well, the first one documented their attempt to transplant sea otters from Amchitka to other locations. Sea otters don't actually disperse very well by themselves. Rafts of males sometimes venture out into the unknown, but it takes them many years to establish new populations because the females tend to like to stay put near where they were born. Especially if there are geographic barriers at play.
Mendel Skulski 24:21
Like, for example, hundreds of kilometers of open ocean between neighboring islands.
Adam Huggins 24:28
Exactly. So the AEC figured that Amchitka had enough otters, and they were about to bomb it, right? So they took the liberty [laughs] to capture dozens of otters and placed them in these tiny little... uh... water closets?
Mendel Skulski 24:42
I mean, that's a bathroom. You mean like glass boxes full of... water.
Adam Huggins 24:48
What would you call them? Water coffins?
Mendel Skulski 24:50
Water coffins.
Adam Huggins 24:51
I mean...
Mendel Skulski 24:52
Yeah, they're like, they're like, like, like tanks.
Adam Huggins 24:55
Yeah, like little glass boxes full of water.
Mendel Skulski 24:58
Okay.
Adam Huggins 24:58
And they load them up on seaplanes and essentially just dropped them off at locations that... seemed okay. They deposited a whole bunch in several locations in Southeast Alaska, which went on to establish thriving sea otter colonies. But they were also in a generous mood. So...
Mendel Skulski 25:15
Wait... are you telling me this is how sea otters returned to BC?
Adam Huggins 25:22
Totally.
Mendel Skulski 25:24
They're fluffy refugees of the US nuclear testing, like, like they're tiny little draft dodgers from up north?
Adam Huggins 25:33
Yeah, sea otters had been completely extirpated from BC during the fur trade.
Mendel Skulski 25:37
Yep, we're pretty much the world champs at depleting our own natural resources before anybody else.
Adam Huggins 25:43
So, 89 sea otters are dropped off at the west coast of Vancouver Island at a place Checleset Bay. And that becomes ground zero – if you will – for sea otter recolonization of the BC coast.
Mendel Skulski 25:56
That's wild.
Adam Huggins 25:57
So while Jim is out on Attu Island through the 70s and 80s, these populations expand and other scientists start studying them. First in southeastern Alaska, and then off the coast of Vancouver Island, scientists are able to replicate Jim's results.
Jim Estes 26:12
That was probably the most powerful affirmation that the mechanisms were correct.
Adam Huggins 26:19
"The mechanisms" being a scientific term for the intricate web of cause-and-effect mediated by sea otters that results in what is now known as a trophic cascade.
[Rhythmic, suspenseful music plays]
Mendel Skulski 26:31
Which is another term that Bob Payne coined in the 1980s. You gotta hand it to the guy, he really knew how to give a complicated idea a snappy name.
Adam Huggins 26:41
He sure did. And, uh, trophic cascade, the basic idea that, that changes in the abundance of one species at one end of a food chain could have dramatic domino effects throughout the system, has been around since at least Aldo Leopold's writing back in the 40s. But Bob Payne and Jim Estes really put the concept on the map with their work in the North Pacific. And in the 80s and 90s, Jim and other scientists unraveled some of these other impacts of the urchin-otter-kelp trophic cascade. Like for example, when otters are absent and urchins dominate the seabed, seagulls tend to eat shellfish. But when otters are abundant, and kelps dominate, those same seagulls switch over to eating mostly fish.
Mendel Skulski 27:25
Neat.
Adam Huggins 27:27
The simple presence or absence of large sea otter populations has been shown to have significant impacts on kelp forest fishes, bald eagles, sea stars, mussels, and even barnacles.
Mendel Skulski 27:40
[laughs]
Adam Huggins 27:41
As far as Jim was concerned, by the early 1990s...
Jim Estes 27:44
It actually had evolved to the point where the more interesting question almost was, is anything not affected by these animals that live in this coastal system?
Mendel Skulski 27:56
That sounds like an impossible question to answer. But at this point, it seems safe to assume that the answer is no. Right?
Adam Huggins 28:06
More or less, depending on where you are on the coast. But now we're gonna return to Jim and his long term study on Attu Island. Remember, he's been working there every summer from the mid 70s to the early 90s, trying to document in real time, the transformation of urchin barrens into kelp forests as sea otters recolonize the island. The only problem is... it never happens. The sea otter population expands as predicted and the size of the urchins drop, as the otters basically eat all of the largest ones first, but the kelp doesn't start to come back for decades. Meanwhile, Jim and others are doing all this fascinating work we've been discussing in other places on other systems, but for some reason, Attu Island just isn't being cooperative. And that's because Jim later realizes of this really important concept called hysteresis.
Mendel Skulski 28:42
Come again?
Jim Estes 29:01
Hysteresis.
Mendel Skulski 29:04
Okay, one more time?
Jim Estes 29:05
So hysteresis is basically a functional relationship that progresses along different pathways depending upon directionality.
Mendel Skulski 29:15
Okay, I'm still not getting it.
Adam Huggins 29:17
Yeah, that was a very technical explanation. Basically, hysteresis means that if you have two opposing stable states, say, a kelp forest on one hand,
[Chill music begins]
Adam Huggins 29:30
And an urchin barren on the other, how you get from one to the other, isn't just a gradual smooth line. It's not – it's not the same going one way as it is going the other.
Mendel Skulski 29:43
Okay, so there's like there's a bit of inertia in the system and it kind of wants to stay in one state.
Adam Huggins 29:48
Yeah, once it – once it's in that state, it wants to stay there. And to get from one stable state to the other, the system has to undergo something called a phase shift.
[Ominous sound effect plays]
Adam Huggins 30:00
Which, basically, is like a major perturbation that causes dramatic changes in the forces keeping the system in one state or in the other.
Mendel Skulski 30:07
Okay? Like, like sea otters returning.
Adam Huggins 30:09
Yeah, just like that. So hysteresis means that there's this, this lag time, that until the otter population reaches a critical threshold, this system just won't flip from being urchin-dominated to being kelp-dominated. And that's because an urchin barren has the ability to self-maintain, it's got its own kind of agency, to a certain extent. Even under pressure, and so does a kelp forest. In fact, Jim and his colleagues have shown that kelp forests can actually repel urchins on their own.
Jim Estes 30:39
It's just an interaction between the kelp and the physical movement of the water that allows them to kind of beat off the urchin attackers. So that, that, that is an important process, though, in allowing the kelp forest to maintain itself once it has become established, even in the face of some moderate grazing pressure from outside.
Mendel Skulski 30:59
So, basically until you reach some crucial tipping point that shifts the system from one state to the other, it almost looks and feels like nothing's really happening.
Adam Huggins 31:11
And on Attu Island, the otters just never quite reached that threshold.
Mendel Skulski 31:15
Well, what happened?
Adam Huggins 31:17
What, indeed.
[Mysterious, rhythmic beat plays]
Adam Huggins 31:27
So, by the late 1980s, Jim is feeling like his work on otters is nearing its end. Other researchers, many of whom were his students are working on urchin-otter-kelp systems up and down the coast. And his long-term study on Attu just wasn't panning out. But another chance meeting, this time with a wildlife biologist named Don Siniff leads to both Jim and Don heading back to Amchitka in the summer of 1990 for one more project. To characterize the demography and behavior of an apex predator at carrying capacity. Basically, when the ecosystem can't support any more otters.
Jim Estes 32:06
We got funded, we went off to the Aleutians with all of these expectations about what we ought to see in contrasting populations that were down at low levels versus those that were carrying capacity. And Amchitka Island was our root site of a population that ought to be at carrying capacity. And we went to Amchitka Island, we did all this work and nothing worked. You know, nothing fell into line with what the expectations would be. Not only that, and nothing really fell into line with what I knew they had been a decade or two earlier because I work there at that time.
Adam Huggins 32:41
For example, Jim had expected to be able to easily find sea otter carcasses washed up on the beach to study.
Jim Estes 32:47
Prior to that at Amchitka Island, in places where the populations were carrying capacity, we used to find hundreds of them every winter, you know, they'd just be all over the place because they're starving to death. And, so you get a lot of natural mortality in those situations. And those animals starve on the beaches and you find the bones and carcasses and eagles feeding on them and all that. And that just, that was one of the things that disappeared initially, it was like we couldn't find any carcasses and it just... come on guys go out and look, I know they're there. I work for a couple of years out there. You know, I used to pick up dozens of these things by myself and in a day. And like, no, we've walked the whole coastline of Amchitka. And we have not found one sea otter carcass
Adam Huggins 33:29
For Jim's colleagues and students, this didn't seem that strange. But for him, it was just night and day because he knew what it was like before.
Mendel Skulski 33:39
Talk about shifting baselines.
Jim Estes 33:41
I was just befuddled, really, I mean, I just thought that's – that's just got to be one of the most monumental failures of... I felt defeated and we left Amchitka Island
Adam Huggins 33:51
And he stops off at a dock island on the way and almost immediately gets offered a project studying sea otters there.
Jim Estes 33:58
So I decided to take that project on and we went out to Adak and things just got worse and worse in terms of the befuddlement, you know, the confusion and... it used to be that we could go out and capture otters very easily and it became very hard to catch, very wild and difficult to catch.
Mendel Skulski 34:16
Okay, so this sounds really confusing, like, Jim and his team were out there for a couple of years working and just... not getting the results they'd expected.
Adam Huggins 34:27
And it's during this study on Adak, when several other researchers on Jim's team start to see something really unusual.
Mendel Skulski 34:34
What's that?
Adam Huggins 34:35
Killer whales are attacking and eating sea otters in the shallow coastal waters around Adak.
Mendel Skulski 34:41
Whoa... [laughs] so metal. [Bleep] sorry. [Laughs]
Adam Huggins 34:46
[Laughs] What am I supposed to say to that?
[Metal music plays]
Adam Huggins 35:04
Over the course of a field season, they actually see this happen six times.
Mendel Skulski 35:09
Like they see it.
Adam Huggins 35:10
Yeah. Like they actually witness it.
Mendel Skulski 35:12
Oh my god.
Jim Estes 35:13
And at about that time, we started seeing killer whales showing up in the coastal system and... incredible numbers compared to what I'd ever seen in the past. And... then we saw them start to eat some otters and... then our counts of otters just continued to plummet. And, you know, the question was, could it be that the killer whales, for some reason, are the drivers of this? And could it be that the reason that these populations are not behaving like we expected them to behave is because they're actually being driven down by another predator?
Mendel Skulski 35:45
Okay, wait. So, killer whales actually eat the sea otters?
Adam Huggins 35:51
Resident killer whales, like those we know and love here in the Salish Sea, exclusively eat fish ,mostly, mostly salmon. But transient killer whale populations eat mostly marine mammals, including seals and sea lions and the like.
Mendel Skulski 36:05
Right. Okay, but those animals have tons of fat and energy, right? Compared to a tiny sea otter. It's like a tic-tac to a killer whale. How many sea otters are we talking about here? How – how big was the decline?
Adam Huggins 36:21
One of Jim's colleagues calculated that about 40,000 animals would have had to have disappeared in the study area to cause the declines that they were seeing in the 90s.
Mendel Skulski 36:30
Oh, okay. That... that seems like a lot of animals for just a few killer whales to to deal with.
Adam Huggins 36:38
That's what Jim thought at first.
Jim Estes 36:40
How in the world did so many otters get eaten. There aren't enough killer whales out there to eat that many otters – that was my initial expectation. And so, I thought, well, how can we address the question of how many it would take and there were – it was obvious really pretty obvious with a little thinking. One was, how many got eaten? And two, how much of value is there to a killer whale... for eating an otter?
Adam Huggins 37:10
And it just so happens that Jim's wife, Dr. Terrie Williams, had the tools to answer these questions.
Jim Estes 37:17
We were having breakfast one morning and we're talking about this. I mean, she's a physiologist and said, you know, how much is an otter worth? And she said, well, I'm not really sure, but we could determine it very easily. Let's just get some carcasses and we'll bomb the carcasses.
Mendel Skulski 37:31
Why is so much of this episode about bombing things?
Adam Huggins 37:36
[Laughter] What is that? Uhh...
Mendel Skulski 37:42
Um... okay... so Jim is talking about a... like a bomb calorimeter here, right?
Adam Huggins 37:45
Yeah.
Mendel Skulski 37:46
Okay, so that's basically a pressurized container that allows you to measure the heat energy given off with some amount of biomass would burns inside of it. So it's the same way that we use determine how many calories are in food for all those handy nutritional facts labels.
Adam Huggins 38:06
Which is basically the equivalent of what they were gonna do for the killer whales.
Mendel Skulski 38:09
Right. How many… how many calories is a serving of sea otter?
Jim Estes 38:13
We got a fresh otter carcass from California, she sent it up to UC Davis. They've got an animal grinder up there because they've got this big animal science lab, you know, they grind up cows and sheep and all kinds of stuff for nutritional analysis. Sent it up to Davis. Little ripe, but you know, there was enough intact and she set it up with an undergrad, a student that worked in her lab there, and they put this thing in this grinder and they turned it on.
[Grinder grinds]
Jim Estes 38:43
[Laughs] He actually – actually kind of went into shock... and I guess the sound and just... the student collapsed immediately. Just, you know, so grossed out by this thing. But anyway, created a little otter slurry, brought the slurry back, bombed it and so there we had the data, and what was there...
Mendel Skulski 38:59
Oh. Wow.
Adam Huggins 39:01
[Laughs]
Mendel Skulski 39:02
That's kind of gross, but kind of awesome too. In the name of science...
Jim Estes 39:07
We knew how much each one of them was worth, we knew what the field metabolic rate of a killer whale was. And so we simply asked how much is a killer whale population getting from all those otters if they ate every one of them? And conversely, how many killer whales would it take to eat that many otters?
Mendel Skulski 39:24
Okay, so what did they come up with?
Adam Huggins 39:27
Well, Terrie ran the numbers.
Jim Estes 39:29
And she came in one morning and said, I just did the numbers last night and it's like 3.2 killer whales or something. And I said, that can't be. She said, I'm sure, I've done it twice to make sure. You've got a decimal point wrong somewhere, you know, that can't be.
Adam Huggins 39:44
But those numbers... they were right.
Mendel Skulski 39:47
Wait. Just. Three. Killer whales.
Adam Huggins 39:51
That's if it was only three killer whales that kind of developed this taste for otter and then only ate otter. If they only ate sea otters occasionally, like maybe even 1% of the time, it would have only taken 300 killer whales across the Aleutians to drive the otters down like that.
Mendel Skulski 40:09
Holy [bleep].
Adam Huggins 40:09
And there were definitely more than 300 transient killer whales in the North Pacific.
Jim Estes 40:14
So what it basically tells you is that an animal like a killer whale, a big, metabolically active predator like that can have an effect that is massive on the system. It was intuitively surprising, I suppose. Uh, I think logically, there was nothing really all that complicated about what we did.
Adam Huggins 40:32
The killer whale hypothesis also helped explain other observations Jim had made, like how they couldn't find any carcasses for all of these dead otters. And how sea otter populations in the sheltered lagoon called Clam Lagoon on Adak Island, which is inaccessible to killer whales hadn't declined at all. Well, everywhere else across the Aleutians they had. bookmark
Jim Estes 40:53
I couldn't really quite get my head wrapped around the whole reason for it, but as we started getting onto the killer whale hypothesis for the decline of the otters, it... all this stuff started to fall in line. You know, it just started to all make sense. And once it started to all make sense, I think the only thing that I was worried about at that point is I'm... have I gotten to a point where I'm trying to rationalize this now? Or is this really objective? Is it really true? And, you know, I spent a lot of time pondering that, I spent a lot of time asking critical colleagues, uh, I pretty much got to the point where I stopped worrying about that.
Mendel Skulski 41:29
Or how Jim Learned to Stop Worrying and Love the Bomb Calorimeter.
[Ba Dum Tiss sound effect]
Adam Huggins 41:36
Yeah, and not everybody loved this hypothesis, least of all, the killer whale community.
Jim Estes 41:44
But it was the only game in town that made any sense and the evidence was reasonably strong. It was not definitive, and never will be, but it was reasonably strong.
Adam Huggins 41:53
That didn't stop this study from being published again in the journal Science, making international headlines, and finding its way right back into those ecology textbooks.
[Mysterious music plays]
Mendel Skulski 42:15
Okay, so I am bothered by one thing here.
Adam Huggins 42:19
Yeah?
Mendel Skulski 42:19
Where were all these killer whales back when Jim was doing his original studies on Amchitka and Adak in the 70s? Why do they just start eating so many sea otters all of a sudden in the 80s and 90s? bookmark
Adam Huggins 42:33
Yeah. Jim wanted to answer this question too. And this is where his work went from being provocative to being... downright controversial.
Mendel Skulski 42:42
Oh yeah?
Adam Huggins 42:43
I won't go into all the details of the controversy because I think they say more about the scientific community than they do about actual science. But essentially, Jim took the notion of the urchin-otter-kelp trophic cascade, and just exploded its boundaries.
Mendel Skulski 43:00
What do you mean?
Adam Huggins 43:01
So here's something okay, killer whales – the Latin name is Orcinus Orca – are actually the largest members of the dolphin family.
Mendel Skulski 43:10
Yes.
Adam Huggins 43:11
They are cetaceans along with other whales, but they're actually in this whole other family, the Delphinidae, which you know, has dolphins.
Mendel Skulski 43:19
Right.
Adam Huggins 43:20
So why are they called killer whales?
Mendel Skulski 43:23
Uh... I thought I knew why – they, I mean, I previously presumed that they are scary whales that kill but the the way he posed this question makes me think that maybe I don't quite have that right.
Adam Huggins 43:41
[Laughs] This is gonna blow your mind. Alright, so as far as I can tell, killer whales comes from a mistranslation of the Spanish "Asesina ballenas" or "whale killers".
[Music]
Adam Huggins 43:55
Throughout the age of pre-industrial whaling, sailors would witness killer whales attacking and eating other whales, often whales that the whalers had killed and were just trying to reel in.
Mendel Skulski 44:07
Oh my god. So, whalers were having to fight off killer whales for their catch.
Adam Huggins 44:13
Yes.
Mendel Skulski 44:14
It's mindblowing. My mind is blown. So killer whales eat whales.
Adam Huggins 44:20
Killer whales... eat whales. They might still do it occasionally, but there just aren't that many whales anymore. In the North Pacific, in the post-war era between the 1950s and 70s, at least several hundred thousand great whales were harvested by industrialised fleets.
Mendel Skulski 44:39
Jeez.
Adam Huggins 44:40
It makes 40,000 otters seem like nothing right, like hundreds of thousands of whales. So when Jim and his colleagues were trying to figure out why killer whales may have suddenly started eating lots of otters in the 90s, they looked back a couple decades before the International Whaling Commission instituted a moratorium on whaling in 1982, when great whales were nearly hunted out of existence.
Mendel Skulski 45:03
Okay, just like sea otters, a hundred years earlier.
Adam Huggins 45:06
Exactly. And here's the thing. Imagine that great whales made up a significant portion of the transient killer whales' overall diet. If you take that away... these are big animals, they need other food sources. And it just so happens that in the subsequent decades, the 80s and 90s populations of harbor seals in the North Pacific plummet, followed shortly thereafter by fur seals, then by sea lions, and finally, by sea otters.
Jim Estes 45:36
Our hypothesis was that it started with whaling, and that one species of marine mammal prey after the next after the next was subject to increased predation intensity, because the killer whales simply didn't have the nutritional resources anymore to support them and they started preying on things like stellar sea lions and harbor seals and eventually sea otters at much higher intensities than they ever had in the past when they had this other super rich and productive and abundant food resource out there.
Mendel Skulski 46:07
That – that's one heck of a set of dominoes
Adam Huggins 46:10
Otherwise known as a trophic cascade.
Mendel Skulski 46:12
That's incredible. Jim and his colleagues traced the whole cascade to post-war whaling.
Adam Huggins 46:20
Yeah. And they published this idea – hypothetically, of course, because it was virtually untestable. The primary merits of the idea are just that it's elegant, and it explains so many things at once. And also, the lack of definitive evidence for another explanation for all of these different declines. So it's not perfect. And after the publication, things got ugly, ugly in a scientific sense in that people started publishing papers that were critical in other journals, and then there were response papers and then response papers to the response papers.
Mendel Skulski 46:54
So catty.
Adam Huggins 46:55
So, I've included a lot of these papers published for and against this hypothesis in the shownotes, for those who wish to dive in, it's actually fascinating. Suffice it to say, what we've presented here is not settled science.
Jim Estes 47:08
You know, I had a – we had – we had a battle with the marine mammal community over whether killer whales ever even ate big whales. And if they didn't, then obviously our hypothesis was totally wrong, you know. But, I think that has been put to rest.
Adam Huggins 47:27
For some in the Marine Mammal community, that is the community of marine mammal researchers, marine mammals declined to comment for this episode of Future Ecologies.
Mendel Skulski 47:36
[Mutters] Why don't they get back to us?
Adam Huggins 47:38
This, and other questions may never be put to rest. We'll probably never be sure whether Jim's hypothesis, which is now known as the megafaunal collapse hypothesis, is true.
Mendel Skulski 47:49
I mean, it wouldn't be the first time that megafaunal collapse had massive impacts across ecosystems. Wouldn't even be the first time on this podcast.
Adam Huggins 47:58
But one thing is for sure. Sea Otter populations collapsed across the Aleutians in the 1990s. And they have yet to recover from those losses.
[Wistful music]
Jim Estes 48:09
Well, in the 90s is when the system fell apart, that's when the otters collapsed, and when the kelp forests shifted from being a kelp system to an urchin system, and we saw that happen. We were living on top of the system when it changed, it was a remarkable thing to see. And it happened very quickly over the course of a year or two. Um... [sighs] it's still that way. The otter numbers have continued to decline. There aren't very many of them. They haven't declined much, but there has certainly not been any recovery. The system – at least the last time I looked at it, or any of my colleagues that have been up there, and it's been a couple of years now, with sea urchins everywhere and no kelp. We hardly ever see killer whales anymore, as it was in the beginning.
[Wistful music]
Jim Estes 49:00
My explanation for that is that there's no reason for them to be there anymore. There's nothing for them to eat – these transient killer whales. The otters are gone, the pinnipeds are gone, everything else is gone. Why show up? Why even come around?
[Wistful music gets louder]
Jim Estes 49:20
Feels like a completely different world. You know, there used to be sea lions all over the place, and there were otters all over the place, and there were a lot of seals around, and all that's gone now. And we have data to document these various patterns. But unless you've seen it with your own eyes, I think it's hard to be quite as impacted by it. You know, I was out there during a time when all of these marine mammals were abundant. And there were thousands of harbor seals at Amchitka Island and tens, or hundreds of thousands of stellar sea lions across Southwest Alaska, and lots of otters and so on and so forth. And now all those things are gone. I mean, there are a few, you'll see a seal here and there now and then. You'll see a sea lion here and there, you know, the otter populations have declined by about two orders of magnitude, you know, by about 98 to 99% of what they were in the early 1990s when we first started working there. So, it's hard. I think you can read those numbers, but unless you've seen it with your own eyes, it just doesn't quite have the impact. You know, I mean, it's done to me... [pause] beyond any reasonable recounting.
Mendel Skulski 50:44
That's tragic.
Adam Huggins 50:46
It's funny that you say that, because Jim doesn't see it that way. He knows these populations are capable of recovery. He's seen that too.
Jim Estes 50:57
I… I don't see these as a tragedy. Except to the degree that it's been so difficult to get people to open their eyes as to the relevance to other systems, to big animals in nature.
Adam Huggins 51:09
I first read Jim's name as the lead author of a paper in 2011 from Science called the trophic downgrading of Planet Earth. In it, Jim and over two dozen co authors lay out examples of trophic cascades they've documented in nature from around the world, including the kelp-urchin-sea otter-orca cascade.
Mendel Skulski 51:29
And by trophic downgrading, they're referring to what exactly?
Jim Estes 51:36
Let me try to explain it the way I did when I taught General Ecology to students. And I would say, imagine a world that had nothing but plants. And the physical environment was not limited to them. There were plenty of nutrients, there's plenty of sunlight, there's plenty of water. Those are the main things that they need, and there will be lots of plants. We have a green world."
Adam Huggins 51:56
This is the world that I want to live in. That's not surprising.
Jim Estes 51:59
Now imagine a world where we have one more element and that is herbivores, things that eat plants with nothing to limit them, other than the food they're eating.
Adam Huggins 52:09
This is the world I actually live in on the Gulf Islands.
Jim Estes 52:13
Under those circumstances, you... at least conceivably and predictably have a world where the plants become very much less abundant. Now add a third trophic level: predators on those herbivores. Conceivably, that those predators on the herbivores will eliminate that herbivore effect, allowing the plants to become as abundant in the system as they would have been where there were no other animals around. And you can take that logic as far up the food web as you want, add another predator and add another predator and add another predator, and it's going to cascade down all the way to the plants. And it's going to do so in a predictable way, so that when there is an even number of trophic levels, that is, two or four or six or eight, you're gonna have a world in which the herbivores are limiting the plants. And when you have an odd number of trophic levels, that is, one with just plants, or three predators, herbivores and plants, you're going to have a world that is very much like one without any herbivores at all. And so that's the basic theory. The otter-urchin-kelp system is an example of a three- trophic level system, where you have predatory otters influencing the herbivorous sea urchins, thus influencing the plants, the kelps in the system. When the killer whales entered the system, they turned that three-trophic level system into a four-trophic level system by eating the otters, and it behaved exactly as that theory would predict and that is – that it became an even-numbered ecosystem. The herbivores became abundant and the plants became rare.
Mendel Skulski 53:56
So trophic downgrading, then is when there's a change up top, that cascades down the system, affecting the plants negatively.
Jim Estes 54:09
In fact, the notion of trophic downgrading is a little more complicated than that. It could operate in a number of different detailed ways. But that in every particular case, if you perturb these higher trophic-level species, expect to see big changes.
[Wistful music]
Adam Huggins 54:29
You could say that we're seeing big changes in the world today. And Jim's work has been critical to understanding them, at least here on the Pacific coast.
Mendel Skulski 54:37
There is a lot going on in this ecosystem.
Adam Huggins 54:40
Yeah.
Mendel Skulski 54:41
But what's amazing to me is that you made it through this entire episode spanning the whole oceanic food chain from toe to tip... without even once mentioning abalone.
Adam Huggins 54:55
I did, didn't I? I guess we better fix that.
Mendel Skulski 54:58
That's next time. In part two of our series on Kelp Worlds.
Adam Huggins 55:04
Thanks for listening. This episode of Future Ecologies was produced by me, Adam Huggins
Mendel Skulski 55:09
And me, Mendel Skulski.
Adam Huggins 55:12
In this episode, you heard Dr. James Estes. Also, Jim gets a huge amount of credit for all of this groundbreaking work. But as we spoke to him, he wanted us to make sure that we recognized all of the students, collaborators and researchers that made these discoveries possible, and that we just couldn't include in this episode. We can't name them all, but special thanks go to John Palmisano, Tim Tinker, Dave Duggins, Jane Watson, Bob Payne, Terrie Williams, Don Siniff, Vincent Schultz and Dan Doak.
Mendel Skulski 55:43
We'll be back next month on the second Wednesday with part two of this series. Please rate and review Future Ecologies wherever podcasts can be found. It really does help the show, and we always love reading what you have to say.
Adam Huggins 55:57
Special thanks to Donna and Paul Homburger. Ilana Fonariov, Anne Solomon and Simone Miller
Mendel Skulski 56:03
Music in this episode was produced by Tidebringer, Ben Hamilton, Leucrocuta and Sunfish Moon Light.
Adam Huggins 56:12
If you'd like to help us make the show, you can support us on Patreon. What you can to get access to bonus monthly mini episodes, stickers patches and more. This season, Mendel is guiding a tour of mushrooms and the kingdom Fungi.
Mendel Skulski 56:26
You'll love it.
Adam Huggins 56:27
Head over to patreon.com/futureecologies.
Mendel Skulski 56:30
You can get in touch with us on Instagram, Twitter, Facebook, and iNaturalist The handle is always futureecologies. You can find a full list of musical credits, show notes and links on our website futureecologies.net.
Transcribed by https://otter.ai and edited by Lauren Man