Salmon Trees

A researcher’s discovery that trees and animals depend on salmon as much as people do has far-reaching implications for British Columbia’s forestry and fisheries policies.

Published April 22, 2015

About Salvaged: In this column we republish seminal articles that helped us look at the world in a new way. While not necessarily the first time an idea or point of view found print, these articles helped shed new light on coastal science or societies. The text has not been altered from its original form.

Nancy Baron’s article, “Salmon Trees,” was originally published in Issue 110 (April/May 2000) of Equinox magazine. Baron tromped through British Columbia’s coastal rainforest with Tom Reimchen, a biologist who advanced the theory that spawning salmon “feed” forests, their decaying bodies importing vast stores of nitrogen to the ecosystem via food webs. This elegant idea helped focus people’s minds on a more comprehensive picture of coastal ecology, moving them beyond considering the components of an ecosystem—trees or fish or bears—to seeing the interconnections of its parts.

Researchers continue to build on Reimchen’s studies. For instance, John Reynolds, from Simon Fraser University in Burnaby, British Columbia, leads one of the world’s most comprehensive studies of the impacts of salmon on coastal ecosystems. Since 2007, Reynolds and his team have studied 50 watersheds on British Columbia’s central coast, looking at the specific impacts of salmon-imported nutrients on a variety of species, from Pacific wrens to freshwater sculpins. He refers to salmon as the coast’s “ultimate engineers,” their impact is so wide-ranging. And, of course, the pressing question back in 2000 is still relevant today: how will the decline of wild salmon stocks play out in coastal forests?


Our 65-foot motor vessel, Blue Fjord, is anchored in Barnard Inlet. The night is cold and wet as we wriggle into hip waders and rain gear and strap on bear spray-laden belts. Then we load cameras, tripods, and umbrellas into the red Zodiac tied to our floating home and head out into the rain for the fourth time since this morning.

Encrusted with mud from days of slogging up and down streams and bushwhacking through rainforest, our ragged-looking crew of six is still eager for the chase. We are trailing researcher Tom Reimchen as he journeys up the northern coast of British Columbia to investigate 55 watersheds for evidence to support his revolutionary discovery about the workings of West Coast ecosystems.

As the Zodiac cuts across the clear waters of the inlet, Dan Klinka, Reimchen’s field assistant, whispers to me, “Tom is the most passionate and driven man I’ve ever met.” Klinka is no slouch himself. Hard-working and unflappable, he is perfectly suited for working with Reimchen—and for researching bears at night. Reimchen’s graduate student, Deanna Mathewson, is equally diligent. Tiny as a gymnast, with blond, Botticelli curls, she is as tough as anyone else on the team.

“You look like a war correspondent,” Reimchen says to photographer Bob Semeniuk, who is dishevelled and slung with cameras.

“You look like Bo-Peep,” retorts Semeniuk. Indeed, Reimchen is wearing the green hood and shoulders of an old slicker over a filthy yellow rain suit. But with his strong features and bobbed red hair sticking out from his hood and cape, he looks more like a deranged Sir Lancelot. Although Reimchen is dead serious about his work, he doesn’t mind laughing at himself. Besides, we’re heading out to watch bears at night. It takes the edge off.

Earlier we had seen swarms of salmon in the estuary, which means that after dark, the place should be crawling with bears. We clutch night-vision monoculars and infrared flashlights—our windows into a hidden world. Over the years of his study, Reimchen has observed that bears fishing for salmon are almost twice as successful at night as during daylight hours, which is why we are heading out now.

The moment the Zodiac pulls away from the lights of the boat, we can see part of the reason why bears have such good luck at night. The wake off the Zodiac’s bow splashes green, and the water churned by the engine leaves a contrail of light. Each drop of rain that hits the water sparkles like a twinkling star. This astonishing display of phosphorescence is caused by a type of plankton called Noctiluca, meaning “night lights.” Any agitation triggers a burst of chemical light from these tiny critters, making the ocean look like a liquid galaxy. Myriad little fishes light up as they flee the boat like thousands of shooting stars going off in every direction.

Near the river’s mouth, we startle an army of salmon. Metre-long chum shoot away like comets, leaving behind a long, luminous tail, each burst of light a physical sensation. We drop to our hands and knees to gaze over the sides of the Zodiac. None of us have ever seen such a spectacle—fish scribbling the water with light. “Aquatic fireworks,” murmurs Reimchen.

Salmon, he tells us, avoid moving—unless a boat passes over them like this—because they light up like lamps when they move, making them easy targets for the bears. Bioluminescence is common in late summer and fall, coinciding with the salmons’ return to spawn. Reimchen speculates that salmon have adapted to this problem by going into a nocturnal torpor out of which they aren’t readily roused. As we step out of the boat and wade into the river’s mouth, the salmon lie like floating logs in the water. When our boots bump against them, they don’t respond.

Following the creek, we enter forest as black as a bear’s coat. We peer through night-vision glasses: it’s like peeking through a keyhole into a spooky, green-glowing world. Wherever we shine our infrared lights, we pick up bear eye shine—two gleaming emeralds in a dark pool. There is bear activity all around us, but we can see only a tiny bit at a time.

The bears shuffle up and down along the creek on trails worn by generations. To establish who is around and how close, they mark trees with scent. Bears are visually sensitive to each other, but at night they seem less leery and fish side by side. One balances on a log in the creek’s centre. We watch in silence as it gropes in the water, grabs a salmon, and retreats into the forest to eat. We can’t see it, but we can hear it, and we wince at the double pop of its teeth biting into the fish’s brain. “Brains are best,” Reimchen says. “Testes are detested.” Tonight the bears are biting off the heads and leaving the bodies, scattering them everywhere. But when salmon are scarce, the bears can’t afford to be so picky. In other areas, we’ve seen entire fish devoured, only the long, earringlike testes left uneaten. Bristol Foster, Reimchen’s long-time friend who is along to video the bears’ behaviour, jokingly suggests that we drape ourselves in testes as bear proofing. Reimchen replies that bears can strip the knackers out of a salmon with surgical precision, so it wouldn’t do us much good.

Tonight, chum salmon are so plentiful that the bears are being very fussy. Time after time we watch one bear catch a fish in its mouth, then seconds later spit it out and try again. When fishing is this good, the bears select for females. If they catch a male, they immediately sense its sex by smell, release it, and try again. Reimchen has found that the captured females are often already spawned out, so the bears’ impacts on salmon reproduction is minimal.

Klinka is having trouble with his infrared beam and clicks it on and off repeatedly. The bear stops fishing and stares in our direction. Reimchen hisses at Klinka to stop. Silence. The bear turns away and resumes fishing. We exhale deeply, relieved. The bear is absorbed in its work, feasting in preparation for winter hibernation. Salmon and bears are doing well this year at Barnard Inlet. When we finally get back into the boat, an elated Reimchen stays up much of the night celebrating the spectacle of plenty.

How bears catch and eat salmon is just one part of a much bigger picture that Reimchen is piecing together to demonstrate the links between the land and the sea. His quest to quantify this relationship began in 1992, but it originated back in 1975, when he completed his Ph.D. in evolutionary biology and moved to Haida Gwaii (then called the Queen Charlotte Islands). For him, Haida Gwaii was a natural laboratory, and he luxuriated in spending 11 out of 12 months in the field, gaining knowledge for knowledge’s sake. He studied stickleback, a small freshwater fish found in the islands’ lakes, which have never been glaciated. He was fascinated to find that these fish showed all the variety and specialization of Darwin’s Galápagos finches and for the same reasons: isolation over a long time and adaptation to their specific circumstances.

Reimchen could quite happily have spent his life examining the evolutionary details of these remote islands, but in the 1980s, when logging threatened to decimate their delicate ecosystems, he was drawn into the battle to save South Moresby. His detailed knowledge of the animals and their habitats was often called up when cases were being made against logging interests.

When, after years of struggle, the Haida, provincial, and federal governments finally signed the park reserve agreement, Reimchen was troubled that commercial fishing by natives and non-natives was allowed to continue in perpetuity around the reserve. “When they enshrined this in the letter of agreement, I was distraught,” he says. “To me, that just undermined the whole thing.” Parks Canada said the fishing was being done sustainably and biodiversity wouldn’t be affected, but Reimchen knew it was ludicrous to protect the land portion alone. “It was clear to me that they were overfishing the salmon and herring, two species that almost everything else relied on, and that the abundance of salmon was the predictor of the abundance of all sorts of other species.”

But Parks officials said, “Prove it,” so he began pondering how to convince the bureaucrats that everything in the ecosystem, from the salmon through to the trees themselves, was intimately connected. He determined to find and quantify all the users of salmon within a representative watershed. If the salmon were not important, he reasoned, then yearly fluctuations or even their disappearance would have little effect on other species. On the other hand, if salmon were the key to the whole ecosystem, as he suspected they were, then fluctuations in their populations would be reflected throughout a whole range of signifiers, including bears. In the fall of 1992, he began this ambitious project in his usual Lone Ranger way: he started searching for a study site in the south end of the park.

In the quiet wilderness of Haida Gwaii, Sitka spruce and western hemlocks form a green curtain above the crisp cut of the high-tide line. Dusty green lichens hang like strands of wool from an insert of alders, a telltale sign that a freshwater stream weaves through the forest to the sea.

In 1992, as Reimchen mused on the problem of how to measure the importance of salmon to species other than humans, he wandered up this stream. Crawling over and under barricades of blowdowns, he noticed that on the plush, moss-covered backs of the fallen giants were littered hundreds of snaggle-toothed jaws, spiky ribs, and clear, cartilaginous medallions, the circular gill covers of salmon. They extended up to 150 metres into the forest. What, he wondered, was responsible for carrying all these fish back into the forest—otters, eagles, martens?

Setting up his tent near the estuary, he sat in the forest, watching and waiting. For days he saw nothing. Then, late one night as he lay in his tent, he heard splashing. Creeping outside, he could make out the inky shapes of several black bears working the stream. He was astonished, because by day he had never seen more than one bear at a time. All night the bears moved back and forth from stream to forest, finally fading away at first light.

Following the biorhythm of the bears, he began staying up all night and sleeping by day.  He determined that under cover of darkness, six bears were working the stream for the biblical 40 days and 40 nights of the salmon run. As he watched them methodically hauling fish after fish into the deep bush, he conceived a whole new understanding of the flow of life between the land and the sea.

The impact of the salmon-bear connection, Reimchen now knew, surges far beyond the streamside. In Bag Harbour, he found that bears took 80 percent of the salmon run into the forest. When the young salmon leave the natal river, they roam the Pacific, feeding and growing until they return to spawn. Then, with the bears’ help, they contribute their maritime harvest to the forest in the form of their flesh. During the 40-day spawning period, he calculated, each bear ferries about 700 salmon, amounting to 1,600 kilograms of fertilizer, far into the woods. Under conditions of abundance, the bears eat less than half of their haul. By Reimchen’s reckoning, this one small stream provided enough salmon for 2 martens, 4 eagles, 12 ravens, 150 glaucous-winged gulls, and 250 crows. When these animals dispersed through the forest, massive recycling continued as they spread nitrogen through their droppings. Decaying salmon also kick-start a maggot population that emerges in spring to feed warblers and flycatchers that arrive famished after their long journey north.

And the nutrient-seeking trees take up whatever is left over. In fact, up to 50 percent of the total nitrogen the trees use comes from salmon. It’s a give-and-take relationship: the salmon fertilize the trees with their bodies at the end of their lives, and the fallen giants provide backwater nurseries for more young salmon. As the trees decompose, their nitrogen is released into the stream, feeding tiny plants and insects that nourish new generations of fish.

Thinking beyond Haida Gwaii to the coast-wide decline of wild salmon, Reimchen reasons that while we worry about the loss of forests and the impact on salmon, the reverse is also a concern: salmon not only need forests but forests also need salmon.

As he pondered the significance of this interdependency, he made an important creative leap: The ambient air is about 80 percent nitrogen 14, but salmon tissue contains elevated levels of a special ocean-originated isotope called nitrogen 15. Therefore, by sampling the trees’ annual growth rings and measuring the relative presence of N-15 through time, he could reconstruct a picture of the historic abundance of salmon and show precisely when they disappeared from, and returned to, a system.

To test this theory, he augered cores through the annual rings from trees in Bag Harbour, then sent them to a [u]niversity in California, where a sensitive mass spectrometer analyzed the presence of N-15. “We got our data from Bag Harbour back, and bingo, there it was: the long-term picture of N-15 and therefore of salmon in the forest.”

But the results were puzzling. In Bag Harbour, the N-15 isotope was virtually nothing, then started to rise radically right after 1900. The question was, why? One possible explanation came from Guujaw, a Haida leader who told Reimchen that the Haida had used Bag Harbour until the late 1800s. After that time, because of smallpox and other problems brought on by white visitors, the Haida moved north. “After the Haida left,” says Reimchen, “perhaps bears came back and resumed fishing for salmon. Bears and Haida don’t coexist on the same streams.”

Reimchen realized that the salmon signature could be a unique window on the past abundance of salmon, and he resolved to test other watersheds in British Columbia to see what their salmon signatures revealed. Finally accepting that this was too big a task to tackle alone, he moved to Victoria, took a teaching position at the [u]niversity, and brought on a graduate student, Mathewson, and field assistants like Klinka. 

He also went to Forest Renewal British Columbia for help but was told that his research had “nothing to do with forestry.” Then the Suzuki Foundation heard about his discovery of the salmon signature and recognized its potential as leverage to change policy on how close logging can come to streamsides. The foundation offered support.

The B.C. Forest Practices code has no exact definition of riparian forest, simply stating that the area along streams must be protected from logging. The width of that strip, however, is controversial, and logging companies are constantly trying to whittle it away. Whereas in Washington State, riparian is defined as a mere 66 feet, Reimchen’s work demonstrates a new functional and philosophical definition of riparian forest that extends far beyond a narrow band, bringing new meaning to author Timothy Egan’s definition of the Pacific Northwest as “anywhere a salmon can get to.” And that, Reimchen reasoned, could be defined by the salmon’s signature.

“Out of the many hundreds and hundreds of watersheds we could examine, we needed to prioritize them,” says Reimchen. Working with the Suzuki Foundation, he ranked the watersheds of the middle and north coasts. First Reimchen and his co-workers looked at Department of Fisheries and Oceans (DFO) data going back to 1947. “It was a nightmare to get the data on salmon streams from DFO,” says Reimchen. “They wanted a full-scale proposal to see how we were going to use the data—which is public information!” DFO maintained that the data were not reliable, but Reimchen suspects that part of the reason they balked was because the news was not good. Although the salmons’ cycles fluctuate from year to year, in general, according to DFO’s own data, salmon returns have decreased 85 percent since 1947.

Next they approached the provincial Ministry of Environment to examine its data about which watersheds had bear activity. Then they overlaid this on the data pertaining to salmon streams, and “big surprise,” says Reimchen. “The watersheds with high grizzly values corresponded with the highest-value salmon streams.” Finally they cross-referenced those with the sites most immediately threatened by logging. This formed the logic for the choice of the 55 watersheds that Reimchen was examining on this expedition up the coast with Klinka, Mathewson, and Foster as his assistants, coring trees, collecting plant samples, studying bear and salmon interactions, and filming their activities.

Still anchored in Barnard Inlet, Reimchen calls us on deck very early the next morning. The white heads of eagles dot the beach and festoon the trees. A tawny wolf is flopped out on the seaweed at the estuary, catching the early rays of sun. Four crows and two great blue herons stand in a circle around it. It looks like a scene from the peaceable kingdom. The animals seem relaxed, as though they have eaten too much.

Piling back into the Zodiac, we motor to the estuary. The headless salmon have all disappeared, so we wander into the forest to look around. The woods reverberate with raven music—croaks, clicks, gronks, and bell noises. Ravens drift through the trees like black phantoms, searching for pieces of fish. A concert of sounds leads us to where they are excitedly watching a bear fishing. They fly around positioning themselves for better views, commenting loudly on what they see.

The bear, a big black male with a brown bum, catches a five-kilogram chum and, trailed by its black groupies, climbs about 25 metres above the creek, where it sits on a moss-covered log to eat the fish. It eats daintily, holding the salmon like an ice cream cone and savouring every bit. It rolls its eyes and runs a long pink tongue around its muzzle. The fish’s flesh hangs in red strips. One bold bird nibbles at the tail of the salmon while the bear is still eating the head, but the bear pays no attention. Dropping the cone part of its catch, the bear shuffles off to resume fishing while the pack of ravens lunges in to feast on its leavings. We shake our heads and look at each other. Our experience in Barnard feels almost holy. Yet this is probably only a fraction of the richness of life that once lived here.

But many other watersheds that Reimchen visited this summer showed none of this abundance. Near the mid-coast First Nations village of Oweekeno (Rivers Inlet) once famous for some of the best salmon fishing on the B.C. coast, there were no salmon at all. When he was there in late August, Reimchen hoped that the salmon were simply late returning, but he was troubled by what he saw. “The whole of Rivers Inlet was murky because it’s been extensively logged,” he says. At the head of Rivers Inlet sits Oweekeno Lake, which drains into the inlet. “Three rivers we looked at above the lake were clear,” says Reimchen, “but salmon that had made it that far had to swim up a murky river and through a murky lake to get to the rivers above that weren’t logged.”

Last autumn the residents of Oweekeno waited in vain for the return of 300,000 sockeye. For a place that historically boasted annual returns of more than three million sockeye, this seemed a modest expectation. But by the end of November, only 3,500 sockeye had made their way home. The people were not the only ones waiting. Also waiting were the bears living among the streams above Oweekeno. By November, starving grizzlies began turning up in the village. Like some apocalyptic nightmare, the famished bears began sleeping in yards, wandering the streets, and scratching on doors in desperation.

Tom Gottselig, Oweekeno’s fisheries officer, describes the horrible situation. “They come in and everybody waits. Nobody does anything, but there comes a point when they are trying to get into houses or into the elementary school. At this point, when I see a bear,” he says, “I just wish it wasn’t here. I wish it would disappear. You just know what the final outcome will be.”

By early December, the villagers and conservation officers had shot 13 grizzlies and 2 black bears. They skinned one grizzly and didn’t find a trace of fat on it. “The villagers are mortified by all this,” says Gottselig. “They have a lot of respect for the bears. It’s been very hard on everybody. This was once a land of plenty, and now we’re really in dire straits.”

Gottselig doesn’t know whether it was logging or ocean warming or overfishing in northeast Alaska, but he admits that at least some of the problems are in the community’s own front yard. “The estuary out front has been covered with log debris from years of just dumping the logs here. It looks like they’ve lost about 25 to 30 percent of the estuary—prime salmon rearing ground. It would have been preventable if they had just done everything dry sort—put a barge on the lake and done the sort there. It might have cost a bit more money, but what’s an environment worth? I think the salmon got hit from every single angle this year.” He pauses, then adds grimly, “Next year is the beginning of the down cycle; it could make this year look good.”

While Gottselig is legitimately concerned about the effect of salmon decline and logging policy on the human population, Reimchen speaks for the bears. “Right now,” he says, “the other users of salmon are not relevant in terms of any fisheries policy. The requirements that bears have—the fact that 70 percent of their yearly consumption of protein has to come from salmon—enters no fishery policy. The timing is critical, since the bears need the energy to tide them over their winter hibernation and they have no fallback systems. When DFO says, ‘Okay, you guys, you can fish for three days this year and take in your two million units,’ they give no units to the alternative users of this resource. None of the quotas required for users besides humans are factored in.” 

And as Reimchen now knows, the other users are not just the bears but also the ravens, the gulls, and the martens, as well as a multitude of marine and insect life. Even the trees and the songbirds that nest in them rely on the salmon. Reimchen takes no satisfaction in the fact that he was right all those years ago. “We’ve been headed this way a long time, but it has never come to the forefront,” he says sadly. He is adamant that a lot of things have to change if we want to save not only the salmon but all the other lives that depend on them. Now that the irrefutable evidence is in, he wants to see action by the bureaucrats. We must start factoring the needs of other species into our fisheries allocations.

For when the salmon fail to show, the whole forest is in terrible trouble.