In their role as top predators, wolves and cougars nurture ecosystems. OSU researchers William Ripple and Robert Beschta have documented this “trophic cascade” in Yellowstone and Zion national parks.

In a remote corner of Zion National Park, a small herd of mule deer browse quietly. Through the sun-dappled canyon burbles North Creek, its waters cool and clear, its banks green and reedy, alive with frogs, butterflies and bird-song. But this pastoral scene in southern Utah has a dark subtext, subtle yet unmistakable in the taut posture of the animals. Their heads come up often, their eyes scan the landscape, their long ears swivel this way and that, alert for the snap of a twig, the crouch of a tawny haunch. Cougars are on the prowl.

In this “landscape of fear,” the highly vigilant deer move across the terrain quickly. Lingering too long beside rivers and creeks, far from escape routes, is risky. So in a predator-rife ecosystem like North Creek, sparse numbers of deer browse less intensively, leaving more uneaten vegetation behind. OSU researchers William Ripple and Robert Beschta call this behavior “risk-sensitive foraging.” The result — low disturbance to soils and organisms in fragile riparian zones — is a huge boon for the ecosystem, the scientists say. “In our research, we’re seeing a significant behavioral shift among deer and elk resulting from this fear of being preyed upon by large carnivores,” explains Ripple, a professor of forest resources in OSU’s College of Forestry. “We think this vigilant behavior, in which ungulates are constantly alert and moving, may be having a large, positive effect on ecosystems.” As evidence, he points to a second canyon just over the ridge, where cougar are rare. The teeming biodiversity of North Creek forms a stark contrast to Zion Canyon, which is close to the roads, parking lots and other amenities that draw tourists, repel cougars and attract deer. Ripple noticed the startling difference one day when he was standing along the shady streambed with a clipboard, recording data as Beschta called out measurements. He was casually observing the many colorful butterflies — the swallowtails and monarchs, the satyrs, sulphurs and spread-wing skippers — fluttering above gaudy bursts of wildflowers. The life forms around him were rich and abundant. “I was practically stepping on frogs and toads, they were so thick,” Ripple recalls. But nearby Zion Canyon, the comparison site for the study, had a relative paucity of species. At that moment, the professors decided to broaden the focus of their study from trees and streams to species abundance and biodiversity. What they found in Zion Canyon were stream banks badly eroded and largely bereft of such “indicator” species as cattails, scouring rushes, Welsh asters and cardinal flowers. At North Creek they found canyon tree frogs and red spotted toads to be 100 times more common, lizards three times more common, and butterflies five times more common than in Zion Canyon. Even populations of native fish, such as the speckled dace and the virgin spinedace, appeared to be higher in the cougar-friendly ecosystem.

Lords of the Rings

However, it was Zion Canyon’s missing trees — the cottonwoods that typically grow thick along healthy river systems — that reaffirmed for the two OSU researchers what they have been seeing in other areas of the West: the pivotal role of cougars and other big predators, particularly wolves, in maintaining ecosystems.

“A deep chesty bawl echoes from rimrock to rimrock, rolls down the mountain, and fades into the far blackness of the night….Only the mountain has lived long enough to listen objectively to the howl of a wolf.” Aldo Leopold A Sand County Almanac, 1949

The two forestry professors, independently, had long been interested in riparian tree species — cottonwoods, aspen, willow — which are diminishing in Western landscapes. In 1996, Ripple heard a presentation by fellow forestry professor Beschta about the malfunctioning ecosystem in Yellowstone National Park, as evidenced by stressed tree populations. “At that time, I was interested in aspen — not predators, not wolves, just aspen,” Ripple recalls. “Bob talked about aspen trees in Yellowstone becoming decadent, disappearing, dying out. And young ones were not growing to replace the old ones as they died. Entire groves of aspen had disappeared in recent decades.”

The mystery of the dying aspen captured him. So, with his then-Ph.D. student Eric Larsen (now a professor at the University of Wisconsin), he headed to Yellowstone. While he was there, he had an epiphany of sorts — not in the field, but in the visitor center. Hanging high on the wall was a large poster, a magnificent photo of a yellow-eyed wolf standing in a thick grove of healthy aspen. “The wolf’s stance made him look like the guardian of the aspen,” Ripple reports. “I suddenly thought, ‘Hey, wolves protect aspen.’” What he and Larsen found confirmed his hunch — a hypothesis first advanced by the father of wildlife conservation, Aldo Leopold, more than a half-century before: that large carnivores are critical to maintaining healthy ecosystems at every trophic level — that is, every link on the food chain. “We found that aspen tree regeneration has diminished since the 1930s, beginning soon after all the wolves were killed off,” he says. In the recent Zion study, the latest in nearly 10 years of cumulative research supporting their hypothesis, Ripple and Beschta turned up still more evidence. After measuring trunk diameters, taking core samples and counting rings, they found an astounding cottonwood age gap between the two canyons. The number of cottonwoods taking root and growing to maturity after 1940 was 38 times higher in North Creek than in Zion Canyon — 892 trees per kilometer compared with 23 trees per kilometer — as reported in the journal Biological Conservation in December 2006. What happened in 1940 that caused cottonwoods to crash in Zion Canyon? According to the scientists, the precursors to the collapse occurred a couple of decades earlier, causing a chain reaction all the way down the biotic pyramid. This “trophic cascade” — a top-down domino effect in which carnivores affect herbivores, and herbivores affect plant biomass — hinged on the disappearance of the big cats, which were driven to more remote reaches of the park when tourists, drawn by Zion’s sculpted cliffs and canyons, began coming by the busload. Established in 1918, the park saw visitor numbers quickly balloon. In the 10 years between 1924 and 1934, yearly visits grew eight-fold, from 8,400 to 68,800. (In 2006, more than 2.5 million people visited the park.) As crowds became bigger, cougars — notoriously shy, elusive animals — became noticeably scarcer. As early as 1938, park naturalist C.C. Presnall warned of the impending imbalance. He wrote, “Human use of the park was, and no doubt always will be, concentrated in Zion Canyon, causing profound changes in the delicate balance between deer and their natural predators.” Unafraid, the deer in Zion Canyon browsed at their leisure. Young cottonwoods, a mule-deer delicacy, were largely devoured, leaving few seedlings to sustain the groves of gnarled giants, whose leaves quake playfully in the wind, whose branches shelter birds and shade streams, and whose roots anchor soils.

The Packs Are Back

The Zion study, funded by the National Park Service, replicates the mounting body of findings by Ripple and Beschta, now an emeritus professor who has retired from the classroom but not from the field. In study after study, region after region, landscape after landscape, they have found the same ecological benefits from “apex predators” — the big carnivores at the peak of the ecological pyramid. The layered sandstone, limestone and shale of the desert southwest, the craggy timberlands of the Rockies, the vast openness of the Great Plains all share that common ecological mechanism — the trophic cascade. “The signature we’ve been seeing on all these sites,” says Beschta, “is the removal of the top carnivore, causing systems to decline.” This ecosystem unraveling happens not only because the actual killing declines, but also because the fear of being killed diminishes. Fearful foraging, quite simply, spares plants, which provide food, habitat and soil stability for the myriad organisms at the base of the biotic pyramid. In the 1990s, ecologist Joel Brown coined the term “ecology of fear” to describe the phenomenon. These kinds of top-down species interactions have been reported by scientists in diverse ecosystems from the Bering Sea to the tropics.

Yet another recent OSU study points again to that same signature. In South Dakota’s Wind Cave National Park, the scientists discovered that new cottonwoods and bur oaks virtually stopped taking hold in the late 1800s and early 1900s, when wolves, grizzlies and other big meat-eaters were wiped out. “So to the question, Do wolves have a role in maintaining ecosystem integrity?,” Beschta remarks, “the answer is ‘Yes’ in capital letters.” Ripple’s graduate students are continuing to build upon the evidence base laid by Ripple and Beschta. Jeff Hollenbeck, a recent Ph.D. student, evaluated potential trophic cascades effects on aspen condition and cavity-nesting birds in the northern Yellowstone ecosystem. Joshua Halofsky, a landscape ecologist with the Washington Department of Natural Resources, is just completing his doctoral thesis studying the potential link between plant growth and elk behavior in Yellowstone and how the presence or absence of wolves affects that link.

“Herbivore population sizes will be determined by the supply of lions, tigers, leopards, cougars, cheetahs, hyenas and wolves, not by the supply of grass.” David Quammen Monster of God, 2003

Ph.D. student Cristina Eisenberg, who lives in the wilds of Montana (see sidebar), is working with an interagency research team in Montana’s Glacier National Park and Alberta’s Waterton Lakes National Park (an area spanning the U.S.-Canada border known as the Waterton-Glacier International Peace Park) to study elk ecology and habitat maintenance. The team includes researchers from the universities of Calgary and Alberta, as well as OSU. With the help of global positioning system (GPS) radio collars, the scientists will track 50 elk and several wolf packs to learn critical details about how elk forage, travel and interact with humans and wolves. Eisenberg’s role in the $1 million study, funded by Shell Canada and operating with educational, government, industrial and conservation partners, is to investigate trophic cascades involving wolves, elk, aspen and other aspen-dependent species such as beavers and songbirds.

The Apex of Change

In Yellowstone, where the researchers got their first clear glimpse of cascading effects, recent OSU studies suggest that trophic cascades can also work as a powerful means to restore an ecosystem. Wolves have made a comeback there, reclaiming their place in an ecosystem that has declined steeply in their absence — ever since ranchers, hunters and government agents exterminated them in hopes of making rangelands safer for cattle and woodlands more bountiful for human hunters. “Putting those predators back into the system again, like the return of wolves to Yellowstone, appears to reverse the process,” Beschta says. Ripple agrees. But he remains circumspect. “Ecosystems are quite resilient,” he says. “The initial recovery of plants since wolf reintroduction in Yellowstone is impressive and exciting to see. We’re hopeful for a pretty strong recovery in the long run, but it could take many, many decades.”

In small Moroccan villages, tea and food accompany discussion. The topic here was water use. OSU water specialist Aaron Wolf (second from left) interviewed Hammou Magdoul (left), a farmer in Ameskar el-Fouqani, with help from his interpreter, Mohamed Zaki (right). (Photo courtesy of Aaron Wolf)

In the summer of 1997, Aaron Wolf and a Berber guide trekked up narrow mountain paths to a village high in the Atlas Mountains of Morocco. Despite the steep terrain, they walked lightly. A donkey carried their gear. As they moved toward snowcapped peaks, they crossed one dry, rocky ridge after another. It took four days for them to reach the M’Goun Valley, elevation 7,000 feet. Their destination was two villages: Ameskar el-Fouqani (upper) and Ameskar al-Tahtani (lower), two communities of mud and stone buildings set among irrigated hillside terraces.

The small spring-fed stream that flows through the villages is vital to the hundred or so families who live here. It serves their homes, powers a grain mill and waters crops and gardens. There is just enough water to meet their needs, but people have arranged to share the stream, doing in a microcosm what nations that divide rivers, lakes and groundwater aquifers do on a grand scale. It was a desire to learn about how a village manages competing demands — through rules that have ancient origins, predating 20th-century European colonization and the rise of an independent Moroccan government — that brought Wolf to this part of the world.

Arid communities with strong links to the past have useful lessons for a thirsty planet, believes Wolf, a water resources specialist and professor in the OSU Department of Geosciences. Traditional arrangements hold practical advice for countries with growing populations and increasing development pressures.

Funded by a grant from the U.S. Institute of Peace, Wolf’s visits to the Berber villages and later to the Bedouin camps of Israel’s Negev Desert documented rules that have worked successfully for centuries. For example, arrangements to share water are often based on time instead of amount. (In one case, families set their irrigation schedules according to when a mountain shadow crosses a stream.) This principle equitably distributes the risk of low-flow conditions during drought years. More typical throughout the world, including the United States, is allocation by volume, which allows some water users to have priority, regardless of how much is available from year to year. In case of drought, other users must do with less or go without.

In Berber communities, water irrigation intakes may be built with stones but not with concrete, guaranteeing a flow of water to downstream users. Following Islamic law, people in both societies do not sell water. Access for drinking is a fundamental right, although making use of canals, pipes and other infrastructure may carry a price tag.

When disagreements occur, they are brought before a locally appointed judge. Enforcement can be swift, Wolf recalls being told. Asked about how long one party to a dispute had to agree to a judge’s decision, the judge replied by wetting his finger and holding it in the wind. “He said that if there was not agreement by the time his finger was dry, he would see to it that the man’s house would be burned to the ground,” Wolf says.

Politics and Databases

Wolf has built a career around assembling global water-related information and expertise, watershed by watershed. In his Ph.D. work at the University of Wisconsin-Madison, he focused on the Jordan River Basin in the Middle East, applying the theory of alternative dispute resolution to create a framework for decision-making. Water, he says, may be the single most important focus for continuing dialogue among Israelis, Palestinians, Jordanians and other groups.

Under the leadership of Director Michael E. Campana, the IWW coordinates water-related teaching and research and applies OSU expertise to the water resources needs of Oregon citizens. More than 80 OSU faculty members in six OSU colleges conduct water-related research, supported by more than $11 million in annual grant funding.

On the Internet, see water.oregonstate.edu.

“If you just talk about the politics, you end up banging your head against the wall. There is no way to move. Every word has 5,000 years of meaning,” says Wolf. “But if you think about the things that are related to this (water), you can find other ways to talk. . . . In my dissertation I set out to capture how water had played a role in the Arab-Israeli conflict over time. And found much to my surprise, because it wasn’t in the literature, there is a rich, rich history of cooperation and dialogue.”

Despite the breakdown of the peace process, he says, multilateral discussions about water continue to this day. The issue is one of personal interest to Wolf who, as a dual Israeli-U.S. citizen, was drafted and served as a paratrooper in the Israeli Defense Forces from 1986 to 1988. That experience, described in his book, A Purity of Arms, instilled in him a deep desire for finding ways to resolve conflict through peaceful means.

In addition to the Jordan, he has worked with organizations to improve management on the Columbia River in the Pacific Northwest, the Salween in Southeast Asia and southern Africa’s Okavango, the “jewel of the Kalahari.” Around the world, the stakes couldn’t be higher. Water development projects are key to social and economic progress, affecting agriculture, energy production, social relations and public health. Inadequate investment already has a staggering cost. The United Nations estimates that more than 1 billion people lack access to clean drinking water and that up to 5 million people, mostly children, die annually of water-related diseases. Some observers have suggested that water wars will haunt the future. “Water supplies are falling while the demand is dramatically growing,” warned Koichiro Matsuura, director general of UNESCO, in 2005.

While Wolf sees access to clean water as a formidable unmet challenge, he disagrees that water disputes will inevitably escalate into wars. It’s not that tension and conflict are absent from water management, he says. Rather, research by him and his students has found that cooperation over water — the kind of traditions exhibited by the Berbers and the Bedouins — is far more common than violence. In scouring historical records and cataloging modern decisions, they have found reference to only one “water war,” which occurred in the Tigris-Euphrates basin about 4,500 years ago. In the last 50 years, nations have signed 400 water-related treaties while 37 disputes involved violence, 27 of those between Israel and its neighbors.

In fact, their research suggests that, far from being an inducement to war, water management can be a pathway to peace. Cooperation over some of the world’s largest rivers — the Nile, the Mekong, the Indus — has succeeded in the face of ongoing hostilities and contributed to productive relationships that make violence less likely.

Building the basis for those relationships, however, is hard work. Wolf and his colleagues have made a start. At OSU, where he is affiliated with the Institute of Water and Watersheds (IWW), Wolf spearheaded creation of the Transboundary Freshwater Dispute Database (www.transboundarywaters.orst.edu), an online library of agreements, case studies and events around the world. It includes maps showing the physical, social and economic circumstances that guide water-related decisions in Asia, Africa, Europe, and North and South America. OSU faculty members in the Northwest Alliance for Computational Science and Engineering (www.nacse.org) built the digital engine that drives the database.

To people struggling with water-related disputes, the database provides invaluable tools. “No matter where you work, people always think they are the only ones facing these issues. Water pollution, upstream/downstream relations, water rights. They’re so relieved just to hear that other people have tackled them,” Wolf says.

“There’s no blueprint for solving conflicts from one basin to another. There are best practices. We’ve done a pretty good job of assembling them. And there are lessons — trends — where basins evolve over time through stages.”

To help people apply those lessons and develop their own practices, Wolf helps to lead a group known as the Universities Partnership for Transboundary Waters. Currently, it includes experts from 14 universities on five continents. “People are grappling with these issues all over, and I want to see continued interaction between Oregon and the rest of the world. We have a lot to teach, and we’ve got some stuff to learn. I think it’s useful to foster a sense of community around this,” Wolf adds.

A recent example of such community-building endeavors focused on Africa. Together with colleagues at the African Water Issues Research Unit at the University of Pretoria in South Africa, Wolf produced an assessment of hydrologic risks and institutional abilities to address them in the continent’s 63 international river basins. The United Nations Environment Programme published their report in 2005, the first of five such continental-scale analyses.

That report has given a boost to people working on water resources management, says co-author Anthony Turton of the University of Pretoria. He credits Wolf with shifting the world’s attention from water as a source of conflict to one of cooperation, with particular relevance for Africa. “I am grateful that he (Wolf) gave Africa a voice,” says Turton. “His project allowed us to speak on behalf of Africa and present some facts with which to counter the prevailing ‘Afropessimism.’ For that, many Africans are grateful.”

“Hydropolitical Resilience”

Key to the ability of countries to cooperate over water problems is a concept that is central to research by Wolf and his colleagues — “hydropolitical resilience.” The term refers to the expertise and resources that organizations need to adapt to changing environmental and social conditions. Countries need both the technical know-how — engineers, scientists, experts in public health and natural resources policy — and ways to integrate the views of people whose lives are at stake — farmers, fishermen and business people. Among these parties, skilled facilitators play a crucial role by guiding negotiations that can be contentious.

To meet these needs, Wolf and his colleagues are building on OSU’s legacy of expertise in water science and engineering. The Water Resources graduate program offers students science, engineering and policy tracks. And a new program in Water Conflict Management and Transformation includes a graduate-level professional certificate for people to be trained in the principles and practices of conflict resolution.

“When you ask people in the water field what skills they wish they had more of, (they point to) how you dialogue, how you listen, how you identify common interests. Technical people are very good in many places, but they need people who can run these processes more efficiently,” says Wolf. “I see us being a training ground for anyone working in water.”

He also sees Oregon’s water management experience as a model for others. “Our watershed councils are doing cutting-edge work in terms of local management and local participation. Power really is vested in the local community.” With funds from the U.S. Geological Survey and IWW, Wolf and OSU sociologist Denise Lach are documenting the successes of Oregon’s local councils in resolving conflicts.

Respecting local knowledge and values can make all the difference, he adds, in the midst of a competition for resources. “You see it a lot in native systems. There’s a balance of equity and honor. In a Bedouin land court, I heard a judge tell someone (who won a case), ‘You’re right, but he (his opponent) still needs a livelihood for his family. Can we think of a way to make sure he still has his minimum needs taken care of?’”

Water management, Wolf and his colleagues stress, is conflict management.

• Aaron Wolf’s Web page
• OSU Department of Geosciences
• College of Science
• OSU Institute of Water and Watersheds
• United Nations Environment Programme
• U.S. Institute of Peace
• National Science Foundation
• U.S. Geological Survey
• Transboundary Freshwater Dispute Database

For more information about OSU’s international water research:

• Water Conflicts in Africa Strain Political, Economic Systems (OSU press release 12-5-05)
• OSU Role Expanding in Managing World Water Conflict (OSU press release 3-20-03)
• Water issues solvable in Israeli-Syrian peace talks (OSU press release 1-25-00)