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Earth Day Reflections on the Potomac
I spent last week in Washington, DC, talking about wolves. I visited the Island Press office and gave seminars about the ecological value of keystone predators to the World Wildlife Federation, and to US government agency directors and leaders. I had come at the invitation of Anne Post, US Fish and Wildlife Service (USFWS) librarian, and Mark Madison, USFWS historian and archivist, to visit the National Conservation Training Center (NCTC), in Shepherdstown, West Virginia. They wanted me to create a televised training seminar for all USFWS offices about predators and how they touch all members of a food web and thus create healthier ecosystems, termed “trophic cascades.” I was also there to give a public talk about my book, The Wolf’s Tooth: Keystone Predators, Trophic Cascades, and Biodiversity. Over the years, other NCTC conservation lecturers had included many Island Press authors, such as Aldo Leopold biographer Curt Meine, and founding father of the science of conservation biology, Michael Soulé. It was humbling to be included among them.
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Creating Resilience: Trophic Cascades and Climate Change
Ecologist Robert Paine summed up the effects of keystone predator removal by saying, “You can change the nature of the world pretty simply. All you need to do is remove one species.”
In The Wolf’s Tooth, I compare ecosystems from which carnivores have been removed to a game of Jenga. This game involves removing wooden blocks one at a time from a tower without causing it to collapse. As you remove them, the tower starts to teeter, loosening some of the blocks, making them easier to remove. Eventually the whole system collapses.
In an ecological game of Jenga in an aspen forest, you might begin by removing species that may seem redundant. If you remove the black-capped chickadees first, not much happens, the system continues functioning more or less as usual. The number of chestnut-backed chickadees increases to fill the gap left by the black-caps. If you remove short-tailed weasels next, the mouse population initially increases, but then the coyotes start eating the surplus mice, as do the northern harriers, and mouse numbers go back down to the level they were at before you removed the weasels. A casual observer might not notice much missing. If you continue by removing white-tailed deer, the other ungulate species carry on, filling in the gap by producing more elk and moose. . . .Read more »
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Why the Earth is Green: Trophic Cascades on Land and Water
We have been discussing the powerful and essential ecological link between apex predators, their prey, and the foods prey eat. Based on the revolutionary ideas of Hairston, Smith, and Slobodkin, who in 1960 ingeniously proposed that the world is green because predators limit their plant-eating prey, trophic cascades science has since then explored the consequences of predator removal from ecosystems worldwide.
In all ecosystems, researchers have found a strong link between predator removal, plant community simplification, and reduced energy flow. Lacking apex predators, ecosystems become capable of supporting fewer species, because the trees and shrubs that create habitat for these species have been over-browsed. With top predators in them, they contain richer and more diverse habitat, and thus can support a greater number of species such as songbirds and butterflies. Apex predators are thus thought to exert top-down effects on ecosystems.
A picture is worth a thousand words. . . See the pictures and read more »
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Aldo Leopold and the Mark of the Wolf’s Tooth
In the early 1900s, while cruising timber as a young forester, American conservationist Aldo Leopold, founder of the science of wildlife biology, encountered a female wolf with her pups. The common wisdom of that era was that the only good predator was a dead one, so he and his crew opened fire. But as he stood there watching the “fierce green light” fade in the wolf mother’s eyes, he felt a sharp, surprising pang of remorse. It would take him decades to parse out his feelings about her death.
In 1935, Leopold bought an abandoned farm in southwestern Wisconsin as a hunting reserve. Today known as the Leopold Memorial Reserve, this land, which he and his family dubbed “the shack,” became the site of some of his deepest lessons about the ecological value of predators. In shack journals between 1939 and 1940, he noted that deer were nipping plants and trees down to eighteen inches in height. In a 1940s game survey, he found that humans had eliminated wolves throughout North America, causing an explosion in deer and elk numbers, and resulting degradation of forests through over-browsing. Meanwhile, back at the shack, deer calmly stood their ground in the absence of wolves, chronically browsing tender young saplings to death.
Near the end of his life, in possibly his most famous and poignant essay, “Thinking Like a Mountain,” Leopold reflected on his early encounter with that mother wolf and the wildlife management implications of her death: “While a buck pulled down by wolves can be replaced in two or three years, a range pulled down by too many deer may fail of replacement in as many decades.” . . . Read more »
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Earth Day at the Shack
Three springs ago I visited the Leopold Memorial Reserve—the depleted Wisconsin sand county farm Aldo Leopold bought in 1930 known as the “shack.” In the 1940s he recorded in his field notes that without large predators such as wolves to regulate their numbers, deer were eating aspens and other trees and shrubs to death. I wanted to see whether this was still so.
The Wisconsin River where it flows near the shack, at flood stage. Photo by Cristina Eisenberg.
The 1900 acre Reserve lies along the Wisconsin River, half in floodplain and marsh, the rest in upland oak-hickory-pine forest and old farmland. Deer densities range from 5-11 per square mile, 150 to 300 percent above management goals. Predators include coyotes, with occasional cougars and black bears. Several wolves have been sighted in recent years, dispersers from northern Wisconsin. These wolves sometimes turn up as roadkill or shot by farmers and hunters. When one was shot near the Reserve a few years ago, the Leopold family mourned its death. Although no established wolf population exists here, more wolves are coming from the north.
The terrible condition of the aspens at the Shack. Photo by Cristina Eisenberg.
I surveyed the Reserve’s aspen stands and found many being eaten heavily by deer. Prescribed fire had stimulated vigorous aspen growth; however, this had only intensified browsing, leaving stands in worse condition than if they hadn’t burned.
One day Aldo Leopold’s daughter Nina joined me in the field. Her chocolate Labrador retriever Maggie ran glad circles around us as we examined the aspens around the shack. As we looked we became aware of missing age classes and ghosts of trees likely long lost to herbivory. “Look,” I said, gesturing toward the aspens, “Lots of old aspens. Lots of young aspens. No middle-aged aspens.”
Next we examined the aspens below the height deer can eat (about six feet). Almost all had sharp, chisel-shaped ends where the deer had bitten off the dominant growth bud. I examined an aspen less than three feet tall and counted its wounds—eight in all. Aspens can sustain moderate browsing, but these Bonsai trees would eventually die.
We looked hard, but couldn’t find stands near the shack with aspens growing above browse height. Across from the shack in Crane Marsh, aspens grew above browse height. But this area contained rough terrain impassable to humans and difficult for even deer to navigate.
When I finished all my fieldwork, I sat on a mossy bench overlooking the Wisconsin River floodplain. It was Earth Day. The sun slanted low across the water and illuminated the white pines planted by the Leopold family. Now grown tall and stately, their boughs swayed gently in the wind. The weather forecast promised snow the next day. I sensed the earth burgeoning with life on that warm afternoon between storms, everything green and growing. Now and then I spotted the bright feathers of returning warblers, flying low between the oaks, exhausted from migration.
Perhaps Aldo Leopold had sat where I sat, hearing cranesong from the marsh, a light wind playing through the previous year’s dried grasses, leaf buds beginning to open after a long, hard winter. Perhaps he had sat here and thought about his struggles as a game commissioner grappling with too many deer in Wisconsin, or about how to sharpen his writing skills to communicate more effectively about conservation. Perhaps he had found hope that his words would open hearts and minds, that his restoration efforts might bear fruit, and that his children would carry on his efforts. And so they have, and the wolves are returning.
There is a great clarity of light here.
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
And Winter Broke
In March I participated in a University of Nebraska literary retreat at the Platte River Whooping Crane Maintenance Trust. It was the climax of spring migration on the river, where sandhill cranes pause to feed during their 5,000 mile journey from Mexico to as far as Siberia. I spent my time there ensconced in a primitive blind with several eminent poets, bearing witness to the cranes’ sempiternal return. Fossil evidence suggests that cranes have been stopping at this place on their journey north for the past 10 million years.
Rough windows cut into the blind overlooked the river and vouchsafed us a view of the cranes as they came down to roost on the silvery Platte at dusk and left to forage at dawn. If we spoke at all, we did so in whispers and gestures, overcome by this primal spectacle, this coming together of legions of cranes into a great council of beings.
Cranes need grasslands, wetlands, and open space. They prefer shallow, broad water for roosting; the Platte River, an inch deep and a mile wide, offers ideal habitat. Accordingly, each spring hundreds of thousands of sandhill cranes and a handful of whooping cranes, spend three weeks in a sixty-mile reach of the Platte. Their annual return is one of the most heartening conservation stories.
While I was in Nebraska winter broke, with crusty snow carried downstream by the river and cranes on the wing filling the air with their clarion calls in the gloaming. I watched bright runes of cranes parachute in against the strong prairie wind after a day spent foraging in nearby farm fields. With sun-gilded breasts, cupped wings, humped backs, and dangling legs they streamed earthward to join their roosting comrades. Their bodies darkened the sky as far as I could see as they streamed in endlessly.
In the 1920s, Aldo Leopold found only five breeding pairs of sandhill cranes and five whooping cranes remaining. This inspired him to write “Marshland Elegy,” in A Sand County Almanac at a time when there was little hope for their survival.
Cranes declined due to over-hunting and habitat loss. Today more than 700,000 sandhill and 280 whooping cranes exist. Legislation (the 1900 Lacey and 1918 Migratory Bird Treaty Acts) helped enable their recovery. In the 1920s, the National Refuge System began to conserve migration and nesting habitat. But it would take decades of wetland restoration and outreach to bring cranes back.
Smudgy contours of landforms lay soft against glowing skies as the light gently faded at dusk. Cottonwoods and river and cranes ribboned horizontally. This landscape and these cranes had shaped each other over eons. My senses filled with the sounds of cranes calling, purring, growling, their songs at once strident and gentle. I sat yearning to understand this vast hegira-the same way that humans over the ages must have sat here witnessing the lessons and truths this great migration holds. This time in this place was about trust: that the future will be better than the near past; that we will reweave the web of life by bringing back species from the brink of extinction.
As dawn broke the next day we discerned among the 100,000 dun sandhill bodies pressed together on the riverbank a blaze of white-a lone whooping crane. Head and shoulders above the others, this great white hope of a bird moved regally amid all the flapping, clamoring sandhills. As it fed it periodically flared its enormous black-tipped wings, and gave loud whooping calls that stood out above the sandhill clamor. Long after all the sandhill legions had spiraled skyward, the whooping crane remained.
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Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Hunting and the Land Ethic
I spent a dozen purple dusks and gilded dawns last December hunkered down in the hoarfrost in coulees, hiding in the rabbitbrush and sage during a late-season Colorado elk hunt. In an area with too many elk and not enough wolves, hunting cow elk provides a powerful conservation tool, because of its effectiveness in thinning herds.
I had convened a science hunt on the High Lonesome Ranch in north-central Colorado. My hunting companions included Michael Soulé, who founded the science of conservation biology, and James Estes, a prominent marine ecologist who studies how predation by sea otters shapes ocean ecosystems. They were veteran hunters, while I was new to hunting. And so these men, who had long mentored me in my science, also mentored me in my first hunt.
As a scientist I study how predation affects whole ecosystems, specifically how wolf predation affects their primary prey elk and how this relationship can influence food webs. Remove an apex predator, such as the wolf, and elk grow more abundant and bold, damaging their habitat by unsustainably consuming vegetation. Lacking apex predators, ecosystems can support fewer species, because the plants that create habitat for these species have been over browsed.
Scientists, such as Aldo Leopold, recognized that apex predators benefit ecosystems in myriad ways by increasing the flow of energy. Yet, given human needs for land use and development, it isn’t possible to have wolves and other apex predators in as many places as they roamed several hundred years ago. In A Sand County Almanac Leopold articulated his land ethic philosophy. He wrote:
“A thing is right if it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise.”
In the 1940s, Leopold was among the first to suggest that hunting by humans, if done properly, can help emulate apex predation. This concept was highly controversial. A lifelong hunter, he had the temerity to suggest harvesting as the most effective way to control the deer population. His suggestion was poorly received by the public. Leopold died long before his ideas about hunting and the land ethic were accepted.
Paradoxically, predation and the primal act of hunting are intrinsic elements of who we are as humans. These relationships are elucidated across the ages in Paleolithic petroglyphs of spear-wielding humans and saber-toothed tigers killing bison. As omnivores, our diet has historically consisted of wild foods harvested from the land, which includes the flesh of other animals. Today, as we strive to live more lightly on the earth, some of us are turning to hunting as both a way to create healthier ecosystems and nourish ourselves with natural, wholesome food.
And so, I got my elk after six days of hard hunting. Afterward, I was filled with gratitude for the gift of this elk. She will feed my family and friends for one year. And her meat tastes of sagebrush and snowy mountains and clear streams and deep wildness—the sort of wildness Aldo Leopold wrote about in his land ethic essay.
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Human Impacts on Natural Systems
As a conservation biologist, I study the ecological effects of wolves on food webs, focusing on their primary prey (elk) and the foods their prey eat (aspens). My work takes place in Waterton Lakes National Park, Alberta, which has many bears in it. Doing wolf research provides essential lessons about the web of life and coexisting with bears.
Bears are considered a “generalist” species, which means that a wide range of habitat and food meets their needs. While they tend to be patient with humans, food issues can put humans in conflict with bears. Which is exactly what happened two months down the line from a series of seven late-spring snowstorms in Waterton in 2010—a force of nature, right?
Well, yes, and no. While the unseasonable snow was undoubtedly a force of nature, this disturbance had an anthropogenic aspect. Human use of natural resources—timber harvest and fossil fuel combustion—increase atmospheric carbon dioxide, causing global heat to rise resulting in weather disruptions. The Waterton storms delayed berry ripening by over one month. While the grizzlies had managed well in the interim by eating roots, shoots, and insects, they had become distinctly out of sorts upon discovering that their favorite berries were unavailable when they wanted them.
I went to Waterton in late August to measure the aspens in a fire area in the Stoney Flats—a large prairie patch that is prime elk winter habitat. Stoney Flats lay three miles up the Wishbone Trail. Bears favored this flat, shoestring route hedged by aspens and berry-laden shrubs, as evidenced by abundant bear tracks and dinner-plate-sized purple scats.
Two weeks before my arrival, a grizzly had bluff-charged a friend photographing mountain goats in one of my study sites, stopping short of physical contact. That summer six bluff-charge incidents had occurred in the park. I hoped that now that the berries were finally ripe, the bears would be so busy eating them that they would ignore us.
My five-person aspen survey crew was configured in a “sandwich” formation—those with the most bear experience in the front and rear, everyone else in the middle where they would be best protected. At the end of our fifth day, we were leaving the area moving briskly, talking loudly, when about one mile from trail head, we heard a heavy thud on the path behind us.
The Stoney Flats grizzly began to follow us, about 20 feet away. I kept our group moving. We looked over our shoulders as he approached, head low, hackles up, jaws clacking, hyperventilating and salivating, dark eyes like coals smoldering into ours. In an even voice, I instructed everyone to take out their bear spray.
He closed the gap between us to ten feet. We kept moving, not breaking our pace, and began to scold him like an unruly child. After about three minutes of this, the bear sat down sideways on the trail. He cocked his head and looked at us—a forlorn, utterly confused expression on his face. Clearly he wasn’t used to humans reacting to him this way, so he stayed put. We continued on our way, and I radioed park dispatch. We returned to finish our work three days later, but never saw the bear again.
Climate change driven by human over-consumption of resources helped trigger the late-season snowstorms. The resulting disruption to the bears’ food supply caused them to take out their frustration on humans. This provides a harrowing lesson as we move into a future that includes a burgeoning human population, escalating use of fossil fuels, accelerating global change and few solutions to these issues. The Stoney Flats grizzly was a messenger. If we open ourselves to the lessons he and his kin have to offer, perhaps we can learn to mend the damage.
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Large Carnivores and Continental Conservation
It’s not exactly safe to be a wolf in Colorado. If you cross paths with the wrong human, you could end up dead. Indeed, for one year those of us working on the High Lonesome Ranch, a privately-owned, mixed-use property managed for conservation, referred to these peripatetic members of the dog family, who were naturally returning to this landscape after being extirpated 80 years earlier, as “visitors from the north.” That phrase was our code to protect the wolves.
In November 2010, the Society for Ecological Restoration (SER) and conservation organization Wildlands Network (WN) convened what amounted to a small village of scientists, managers, and conservation leaders on the High Lonesome Ranch in DeBeque, Colorado, to exchange ideas about reconnecting and rewilding fragmented landscapes and to explore the vital importance of private lands in these efforts.
The principal ranch owner, Paul Vahldiek, Jr., hopes that his management of High Lonesome will serve as a land ethic blueprint for private lands. Vahldiek is using his ranch to demonstrate how reframing our human relationship to nature. The High Lonesome Ranch comprises a sublime, 300-square-mile hunk of north-central Colorado on the west slope of the Rocky Mountains. Its rugged, aspen-crowned mountains and deep river valleys hold healthy deer and elk herds and provide a haven for cougars, black bears, coyotes, and more. Threatened and endangered species returning here include wolf, wolverine, and lynx.
Why is this land such a carnivore magnet? Perhaps because it lies squarely in the center of the Spine of the Continent—a 5,000 mile-long wildlife corridor that extends from Alaska to Mexico along the Rockies. Or maybe because this ranch the size of a large national park gets far less human use than most parks.
Why focus on private lands? Because national parks and other reserves are mere postage stamps in a matrix of mixed-ownership lands subject to hunting, ranching, timber harvest, and energy development. Thus, private land conservation can do much to help mend fragmented landscapes.
And why a continental scale? Because critical corridors, such as the Spine of the Continent, will enable nature to continue to function well by helping restore species, such as wolves, that have a powerful effect on whole ecosystems. They also provide pathways for animals and plants to shift to higher elevations as our climate changes.
Keith Bowers, WN president, opened the workshop by voicing the need to place ecological restoration within the context of permeable, large landscapes to ensure the wellbeing of animals like wolves, cougars, lynx, and wolverines that travel far.
But according to workshop organizers Conrad Reining of WN and Bill Havorson of SER, we can’t achieve continental-scale conservation without addressing local problems, like the invasion of a non-native plant species into a town park. They proposed creating a primer to guide conservation on both local and landscape scales and inform policies that can lead to international restoration.
Landscape ecologists David Theobald and Pete David presented compelling models of wildlife-linkage hotspots, like southern Arizona, where young male cougars dispersing near human communities often meet death on busy highways. Yellowstone-to-Yukon (Y2Y)’s Wendy Francis shared how wildlife overpasses and underpasses in Banff National Park are enabling grizzly bears to survive heavy traffic. These safe crossings provide graphic examples of how local-scale efforts embedded strategically amid vast wildlife corridors, such as the Spine of the Continent, can lead to continental-scale conservation.
The SER/WN continental conservation workshop on the High Lonesome Ranch provided a wellspring of ideas for healing small and big landscapes. As we work individually to restore nature, we will turn these ideas into reality supported by the vibrant network of people the workshop created.
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
Wolves in the Pacific Northwest: Ecology’s Tangled Web
Washington State’s old-growth rainforests are among the richest communities on earth. These ancient forests support astonishing biodiversity due to their high moisture, nutritious soil, and architecture. The Douglas-fir, a formidable tree giant that can live over 1,000 years, embodies these forests’ physical characteristics. Its 500-foot-tall, multilayered canopy, thick trunk, and enormous volume (called “biomass”), whether living or dead, provides home for many species.
Life and death merge seamlessly on the spongy ground, with dead fall acting as nurse-logs to tender saplings—all part of the same continuum. Yet for the past eighty years, these wet, verdant forests have lacked a vital species.
By the 1930s humans removed wolves from the Pacific Northwest. Without the presence of a strong predator, elk exploded in number. Hungry animals rapidly browsed highly edible hemlock and cedar saplings, preventing them from growing into adult trees. Without young trees—the habitat, in turn—diminished in quality. Now many people believe that the wolf’s return promises to create big changes. Or will it?
Since 2007, wolf recovery in Washington is advancing naturally, as the animals travel here from Canadian and U.S. populations. There are now several documented wolf packs and dozens of reliable wolf sightings. Washington State’s progressive wolf management plan acknowledges this species’ powerful ecosystem-regulating role through trophic cascades.
Trophic cascades are the direct and indirect food web effects of apex predators, such as wolves. Directly affecting their primary prey, elk, by killing them, wolves also indirectly affect them through fear. This powerful relationship causes energy to cascade through the food web from the “top-down,” like a waterfall.
Wolves profoundly affect elk behavior, forcing them to nibble plants warily and look up frequently, rather than complacently browsing plants to death. This means that saplings and shrubs are not over-browsed and therefore many grow into trees, thereby improving habitat for a wealth of other species increasing biodiversity. Healthy saplings and shrubs provide more food for other species besides elk. Thus wolves touch everything in a forest, sending energy rippling through the food web from the top-down.
However, energy surges caused by fire or timber harvest, which open a forest’s canopy, allowing sunlight to stream in, also contribute to plant growth. Because this involves nutrients stored in the soil, it is often referred to as a “bottom-up” effect. According to conservation biologist Michael Soulé, in any landscape it is never bottom-up (resources) or top-down (wolves), but rather an intricate weave of both effects.
Scientists found strong wolf-driven cascades in places such as Isle Royale and Yellowstone National Parks. With wolves undeniably here to stay in Washington, what trophic cascades might we see? In Yellowstone, before the wolf’s return, elk had been hedging these plants down to ankle-height. People have noticed dramatic changes in the decade since wolf recovery, such as the tall tangle of flourishing willows and aspens along formerly barren stream banks.
While in Seattle recently to read from my book, The Wolf’s Tooth, I discussed wolf ecology with local authors and wolf conservationists. My writer friends wanted to know whether we would witness similar changes in Washington now that wolves are back. University of Washington professor Jerry Franklin, often called the “guru” of old growth, suggests that trophic cascades in the northwest may differ from those in simpler systems. Things may not be so simple in Washington’s lush, wet forests as in Yellowstone’s comparatively arid forests, where wolf effects are well-documented. In rainforests, as elsewhere, top-down energy combines with bottom-up effects, which include nutrients from moisture and disturbance (fire, timber harvest). And in these moisture-rich forests, bottom-up energy flow may be tremendous.
Nevertheless, because of their role as ecosystem regulators, wolves are highly relevant to Pacific Northwest ecology and conservation. In the 1930s wildlife ecologist Aldo Leopold argued that wolfless forests in Germany and Yellowstone could be considered “empty” forests, because of their significantly altered and diminished food webs. In their recent research on Washington’s Olympic Peninsula, scientists Robert Beschta and William Ripple concluded that wolves wield similar effects here.
Elk undoubtedly have had a strong impact on forest understory plants in Olympic National Park’s valley bottoms. Franklin and others have measured this in two “exclosures”
—large areas fenced to keep out elk—in place for several decades in the South Fork of the Hoh River. Elk have shaped tree communities here by feeding selectively on hemlock, cedar, Pacific yew, and huckleberries.
I visited these exclosures with Franklin two summers ago, and he showed me the powerful impacts of unregulated elk. The exclosures’ sturdy 12-foot fences protected tall, profligate thickets of young trees and shrubs, as well as skunk cabbages (a tasty browse species) eight feet in diameter. Outside, where elk could freely munch trees and shrubs little grew besides grass.
The wolf’s return to the Pacific Northwest will certainly reduce elk density and their effects on communities. Forests here may soon be changing boldly, as tender hemlocks, cedars, and other plants grow beyond the hungry mouths of elk. This could affect everything, down to the soil and the thousands of species it harbors.
However, these top-down effects may be context-dependent: stronger in younger forests that have experienced timber harvest, fire, or volcanic eruption, whose resulting rapid growth of succulent saplings and shrubs attract more elk than ancient, closed-canopy forests. According to Franklin, while it’s quite likely that the wolf will create top-down effects in the Pacific Northwest, as elsewhere, the complexity of these interactions invites deeper inquiry.
About Cristina Eisenberg
Cristina Eisenberg is a conservation biologist at Oregon State University, College of Forestry, and Boone and Crockett Fellow who studies how wolves affect forest ecosystems throughout the West.
