The Ecological and Human-Centered Benefits of Wolf Reintroduction to Yellowstone National Park

Allison G. Kelley
Canisius College

History of Yellowstone

Yellowstone National Park (YNP) was established as the first National Park on March 1, 1872 (National Park Service “History,”i2016). Today the park covers 3,472 square miles in Wyoming and small parts of Montana and Idaho (National Park Service “Park Facts,”a2016). In order to unify the protection and management of all of the national parks, President Woodrow Wilson signed the Organic Act on August 25, 1916, which created the National Park Service (NPS) (National Park Service aHistory,” 2016). Prior to the Organic Act, YNP was seen as solely for people, not conservation; the loss of bison was a loss to people, not the ecosystem. Theodore Roosevelt saw YNP as a natural breeding ground and nursery for game that could overflow into lands outside of YNP and be hunted (Marris 2011). As the United States became more industrialized and more people were living in cities and fewer on farms, attitudes toward nature in general began to change. In the late eighteenth and early nineteenth century, naturalists like Henry David Thoreau and later John Muir helped to instill a love of nature for nature’s sake into the American people. The idea of wildness changed from something savage and perilous to something more romantic. The wilderness became a place to escape the stresses of everyday life instead of something dangerous to escape from. It was from this change in attitude that the “Yellowstone Model” was born; Yellowstone became the example for other parks around the world. This model sets aside areas of pristine wilderness, allowing humans only as tourists, to preserve the environment found within (Marris 2011).

In the Greater Yellowstone Area the late 1800s to early 1900s was a period where many predators, including wolves, were routinely killed by park management and local settlers (National Park Service “Wolf Restoration,”e2016). Settlers saw wolves and other predators as killing machines and competition; wolves were known to kill livestock and “desirable” wildlife species like elk and deer (National Park Service “Wolf Restoration,”o2016.) Due to ecological research in the 20th century, attitudes toward wolves changed. Aldo Leopold was one who helped spur forward this change; in his 1945 essay, “Thinking Like a Mountain,” he said “The cowman who cleans his range of wolves does not realize that he is taking over the wolf’s job of trimming the herd to fit the range. He has not learned to think like a mountain. Hence we have dustbowls, and rivers washing the future into the sea.” Though the mid-1900s, more and more Americans began seeing wolves as an important part of the ecosystem instead of a pest. Eventually, the grey wolf was listed as endangered in 1974 under the Endangered Species Act. In 1975 the long bureaucratic and scientific process to restore wolves in YNP began (National Park Service aWolf Restoration,” 2016).

From 1991 to 1994 the National Park Service, the US Fish and Wildlife Service, and members of the state government, developed a wolf reintroduction plan and environmental impact statement (National Park Service NWolf Restoration,” 2016). In 1995, the Secretary of the Interior approved the plan and set it into action; 31 wolves were relocated from western Canada to YNP (Switalski 2003). Similarly, in 1997 ten wolves from Montana were relocated to YNP (National Park Service “Wolf Restoration,”o2016). By 2001 there were 132 wolves in YNP and 216 wolves within the Greater Yellowstone Area, including Idaho and Wyoming (Switalski 2003). By 2011, the wolf populations of Montana and Idaho were removed from the endangered species list due to presumed recovery and pressure from local citizens. The Wyoming population in YNP is listed as “experimental” due to the fact that it was reintroduced and is still being monitored for improvements (US Fish and Wildlife Service 2016). The Northern Rocky Mountain Distinct Population, besides Wyoming, has been delisted due to presumed recovery (US Fish and Wildlife Service 2016).

Keystone species and ecosystem health

According to Mills et al. (1993), a keystone predator controls the density of a primary consumer that is capable of excluding other species from the community. Wolves are a keystone predator because they control the densities and behavior of an ecologically significant prey species, elk. According to Camargo-Gamboa et al. (2010), when keystone predators are removed from a system, the increased abundance of prey animals leads to intense competition and can drive one or several species to extinction. Therefore, keystone predators maintain biodiversity, the variety of life on earth, through trophic cascades. A trophic cascade is the ecological concept that the behavior and abundance of a predator impacts the behavior and abundance of prey and vice versa.

Greater biodiversity leads to better resilience and stability, so biodiverse ecosystems are more likely to survive disturbances (Costanza 1992; Miller and Spoolman 2007; Camargo-Gamboa, Huerta-Quintanilla, and Rodríguez-Achach 2010). For the purpose of this paper, biodiversity is the key to applying the metaphor of ecosystem health to the Yellowstone ecosystem because, in addition to increasing an ecosystem’s stability, higher biodiversity increases ecosystem functions and services (Gamfeldt, Hillebrand, and Jonsson 2008).

The extirpation of wolves from YNP in the early 1900s led to a trophic cascade that negatively influenced many other species and populations of lower trophic levels within the Greater Yellowstone Area, both through lethal and nonlethal effects (Ripple and Beschta 2003; Ripple and Beschta 2012). Consequently, the park’s goals of environmental conservation, cultural preservation, and education became harder to accomplish. I argue that the reintroduction of wolves to Yellowstone National Park was beneficial to the region because it helped achieve both the ecological and human-centered goals of YNP.

Achieving the Park’s Ecological Goals

Ecological Goals of a National Park

Initially, the ecological goals of YNP were based on the Leopold Report (1963) that stated that the best management practice was to maintain the biotic associations within the park as closely as possible to the conditions that were present before the arrival of white men (Costanza 1992). Yellowstone, like any other ecosystem, is now seen as not in equilibrium, meaning that its ecology is not stable over historic or pre-historic time. Today, park officials manage for improved ecosystem health and resilience, so that the inevitable change an ecosystem experiences will not lead to its collapse (Costanza 1992). The reintroduction of wolves helped achieve this goal by creating a trophic cascade that positively affected many other species, starting with the elk.


When wolves were absent from 1926 to 1995, the number of elk in the park fluctuated substantially (Eberhardt et al. 2007). There are many possible reasons for this fluctuation but the most probable are changes in park management and the presence or absence of wolves.

Eberhardt et al. (2007) found that in 1935, almost ten years after the last wolves were eradicated from Yellowstone, the northern herd contained more than fifteen thousand elk. Eberhardt et al. (2007) speculated that the northern elk population reached its carrying capacity, or the maximum population size that the environment can sustain, of twenty-five thousand individuals in approximately 1988. The period between 1935 and 1968 saw a steady decrease in the elk population due to culling by the National Park Service and hunting by humans for sport or meat until the population hit fewer than seven thousand individuals around 1968 (Eberhardt et al. 2007). This drop in elk population sparked hostile attitudes in the public toward the NPS management practices and led to a series of State Senate hearings resulting in Yellowstone adopting natural management practices for elk populations, effectively halting the culling practices (Parker, 1999). This strategy was not successful; from 1969 on, the rapid increase in elk population size was due to both the adoption of the natural management policy and to the fact that elk were no longer under predation pressure by wolves (Hollenbeck and Ripple 2008; Eberhardt et al. 2007).

After wolf reintroduction in 1995 and 1996, the northern herd of Yellowstone elk saw a decrease of 18% (Ripple and Beschta 2003). Eberhardt et al. (2007) show that the number of elk decreased steadily from about twenty thousand elk in 1995 to twelve thousand elk in 2004. Many attribute the decrease in elk population to an increase in predation by wolves, while others think it was more likely due to other abiotic, or non-living, factors, such as harsher winters and droughts (Vucetich et al. 2005; Garrott & Guide 2005)., Overall, it is not clear if wolves are responsible for the decrease in elk population that has been observed in the Greater Yellowstone Area since 1995, but the scientific community generally agrees that the presence of wolves has altered the behavior of elk which, in turn, affects populations of many other species (Ripple and Beschta 2012; Hollenbeck and Ripple 2008; Ripple and Beschta 2004).

After wolf reintroduction, elk experienced differential risks of predation in different areas. Locations were classified into two broad categories based on the physical characteristics of the landscape: high-risk sites contained components that lowered the likelihood of detection of the predator and the likelihood of escape, whereas low-risk sites contained components that raised the likelihood of detection and the likelihood of escape (Ripple and Beschta 2004). Low-risk sites, or prey refugia, could be an area outside of the core territory of wolves (Ripple and Beschta 2004). Because of this, the renewed presence of wolves in YNP has changed elk behavior and, specifically, where elk spend their time. Ripple et al. (2001) found that, for two habitats, the low wolf-use areas had more than twice as many elk pellets than the high wolf-use areas, suggesting that the elk were spending more time in the areas where there were fewer wolves. This can alter the composition of many other species because the elk now forage in areas different from when wolves were absent from the park (Hollenbeck and Ripple 2008). On average, each elk consumes twenty pounds of plant material a day. Because of this, plant abundance is expected to be higher in high-risk sites for the elk such as in core wolf territory, since elk are less likely to spend time in and forage in those sites out of fear.

Subsequent Effects on Plant Life

The increase in elk resulted in an increase of herbivory on many different deciduous species. There is substantial evidence that indicates that the increase in herbivory led to decline in the recruitment of many deciduous species including aspen, cottonwood, and berry-producing shrubs (Ripple & Larsen 2000; Beschta 2005; Ripple & Beschta 2003).
Prior to wolf reintroduction, aspen growth and recruitment, or when new individuals are added to a population, throughout YNP was stunted because of larger elk populations (Ripple and Larsen 2000). Elk can prevent aspen recruitment by browsing the leaders, the vertical stems at the top of the trunks, off the aspen saplings during the winter. Ripple and Beschta (2012) found that 100% of the aspen leaders in 1998 were browsed, which led to the absence of significant recruitment seen by Ripple and Larsen (2000); however, they also found that this percentage declined considerably over the next twelve years (post wolf reintroduction).
The area with the largest difference in browsing of aspen from 1998 to 2010 was riparian areas with downed logs (Ripple and Beschta 2012). Riparian zones are the transition areas between terrestrial and aquatic ecosystems. Ripple and Larsen (2000) stated that wolves frequent riparian areas for travel and foraging. Because the presence of downed logs would make a site more high-risk, the sharper rate of decline in the browsing of aspen in riparian areas with downed logs following wolf reintroduction could be because elk avoided these high-risk sites. Riparian areas without downed logs had the second highest rate of decline in browsing, showing that the physical presence of the wolves could be enough to reduce foraging by elk in that area (Ripple and Beschta 2012). Therefore, the renewed presence of wolves in YNP altered the behavior of elk, allowing increased recruitment of aspen.

To study the large scale effects of wolf reintroduction on riparian areas, Beschta and Ripple (2016) summarized the results of twenty-four assessments of deciduous woody plants. They found that berry-producing shrubs have increased in height and stem diameter since the reintroduction of wolves. Climate fluctuations have also been suggested as a cause for increased woody plant height (Singer et al. 1998, cited in Ripple and Beschta 2003), but Beschta and Ripple (2016) analyzed years of temperature, precipitation, and snowfall data and found no evidence for a climate effect but rather, suggested that reduced elk herbivory is the most likely explanation for increased height of berry-producing shrubs. They also found that the proportion of shrubs with berries was positively correlated to shrub height (Beschta and Ripple 2016). Therefore, the renewed presence of wolves has not only increased berry-producing shrub height, but it has also increased the number of berries available to birds, bears, and rodents, demonstrating their importance to the biodiversity and resilience of the area (Beschta and Ripple 2012).

Cottonwood trees were also affected by the lack of an apex predator. Beschta (2005) evaluated the history of cottonwood recruitment within the northern Yellowstone elk herd’s winter range and found that cottonwood recruitment was successful overall prior to the 1920s but that there was a significant lack of recruitment in the 1930s and essentially none from the 1940s to the 1990s. This coincides well with the timeline of elk in the park and suggests that the trophic cascade sparked by the loss of wolves may have led to decreased cottonwood recruitment. Further evidence of this comes from Beschta’s analysis of cottonwood recruitment across several different sites in YNP. Two of the sites were inaccessible to elk because of a river, steep banks, and a highway; these sites are essentially natural elk exclosures. Beschta (2005) found that at the sites unavailable to elk, high levels of cottonwood recruitment still occurred in the twenty years after elk culling practices were stopped by the NPS. The sites that were accessible to elk saw virtually no cottonwood recruitment after the 1920s. This study shows that the absence of wolves and the subsequent increase in elk population size had a strong negative impact on cottonwood recruitment.
Beschta (2005) examined the release (increase in total height) of black and narrow-leaf cottonwoods in YNP between high-risk and low-risk sites. They found a positive linear relationship between gully depth and the height of nearby cottonwoods (Ripple and Beschta 2003). All of this evidence suggests that with elk under predation pressure again by wolves, the elk are more likely to forage in low-risk sites, allowing the cottonwood in the high-risk sites to experience increased growth.

The depletion of the plant community during the period when wolves were absent from YNP meant the riparian system could no longer support beavers, and the number of colonies dropped severely (Ripple and Beschta 2004; Beschta and Ripple 2016). Surveys conducted in 1996, 1998, and 1999 found only one beaver colony in the Yellowstone’s northern range, but that number increased to twelve found in 2009 and eighteen found in 2015 (Ripple and Beschta 2012; Beschta and Ripple 2016). According to Ripple and Beschta (2012) it is probable that this increase is due to the increased recruitment of tree species like aspen, cottonwood, and willow following wolf reintroduction.

Beavers are important to ecosystem health because they act as ecosystem engineers; an ecosystem engineer is a species that can create, modify, or destroy a habitat. Beavers are ecosystem engineers because dams can increase habitat heterogeneity and influence many abiotic elements like water table elevations and channel morphology (Ripple and Beschta 2004; Ripple and Beschta 2012; Beschta and Ripple 2016). The loss of beavers from an ecosystem causes a loss of structure and materials that affect energy flow and habitat type which, in turn, can cause the disappearance of other species that rely on those habitats and resources. When present, beavers can increase the plant, vertebrate, and invertebrate diversity. Therefore, wolf reintroduction, and the subsequent increase in the number of beaver colonies, had positive effects on the abiotic context that biotic elements depend upon and strengthened the success of the reintroduction.

Abiotic Elements

In the last century, global temperatures have increased by 0.6°C and are predicted to increase another 1.4 to 5.8°C over the next 100 years (Wilmers and Getz 2005). Yellowstone experienced shorter winters and earlier snow melts during the period of 1950 to 2000 (Wilmers and Getz 2005). Due to the lack of wolves and increased elk survival with shorter winters, there was a dramatic decrease in the amount of late-winter carrion (dead, decaying, animal flesh) available to scavengers. Wilmers and Getz (2005) showed that, without wolves, the amount of late-winter carrion would decrease by 27% in March and as much as 66% in April. This lack of carrion could cause a potential food bottleneck for scavengers and could lead to higher death rates or abrupt prey choice and behavior changes. However, when modeled, the presence of wolves supplied scavengers with carrion regardless of winter severity; the amount of late winter carrion would decrease by only 4% in March and 11% in April. Therefore, wolves acted as a buffer to climate change; their presence lessened the effect felt by scavengers, thereby increasing the ecosystem’s resilience to environmental change (Wilmers and Getz 2005).

New research from Wilmers et al. (2012, 2016) suggests that the top-down control on herbivory by top predators may also help buffer against climate change. Increased autotroph growth across ecosystems could partially compensate for the increase in atmospheric CO2 due to human industrialization. Wilmers et al. (2016) theorized that the top down effects caused by wolves could cause carbon buildup in the woody species that were affected by increased elk herbivory like aspen, cottonwood and willows. If their results are extrapolated to the entire North American range of wolves, the top down effects cause a decrease in carbon production equal to the annual emissions of six to twenty-one million vehicles. Admittedly, these results are preliminary and highly speculative, but this example speaks to the importance of top predators and the potential influence they have on a global scale.

Achieving Human-Centered Goals

The Human-Centered Goals of a National Park

The purpose statement for YNP states that “Yellowstone National Park, the world’s first national park, was set aside as a public pleasuring ground to share the wonders and preserve and protect the scenery, cultural heritage, wildlife, geologic and ecological systems and processes in their natural condition for the benefit and enjoyment of present and future generations” (National Park Service “Guide for Protecting Yellowstone,”u2016). The national park service follows many guiding principles to achieve the park’s human-centered mission including heritage education, citizen involvement, effective management, and productive partnerships, among many others (American Trails 2007). The ways Yellowstone serves to benefit humans can be compiled into three main categories: supporting local communities, preserving culture, and education.
Benefiting Local Communities: Hunting

The renewed presence of wolves in the Greater Yellowstone Ecosystem has also benefited the hunting community, both directly through wolf hunting and indirectly through elk hunting. Wolf hunting is prohibited within YNP, but is a common and profitable activity in the areas surrounding the park (National Park Service aWolf Management,” 2016) and currently legal in Idaho and Montana. In Montana, in 2016, 18,625 wolf hunting licenses were sold and 210 wolves were killed. These licenses cost $29 for an in-state resident and $50 for an out-of-state visitor (Montana Fish, Wildlife, and Parks 2016). Substantial funds also result from poaching fines. In Montana, the fine for poaching a trophy animal, such as the gray wolf, is as high as $30,000. If that animal is transported across state lines, the fine is raised to $250,000 (Curtis 2002). The funds generated from fines, the purchase of hunting licenses, as well as the purchase of guns and ammunition, go toward wildlife conservation programs, law enforcement, and hunter education programs (International Hunter Education Association 2016).

Wolf hunting also provides economic benefits to local communities. Businesses like hotels, restaurants, and even taxidermists in those communities could experience increased economic stability with an increase in the number of people visiting their area, as similar towns centered around wildlife tourism have excelled with a greater influx of tourists (Robbins 2006).

The renewed presence of wolves in the Greater Yellowstone Ecosystem has also facilitated elk hunting, as the wolves maintain a healthy elk population. In the Yellowstone area, Williams et al. (2002) found that hunters had a more positive attitude toward wolf reintroduction than the general population. Similarly, Kellert et al. (1996) found that attitudes toward the wolves by hunters and trappers in Michigan, the only state in the lower 48 where wolves were never extirpated, had an overall positive view of the wolves; they saw the value of them as an economic resource because of the wolves’ ecological importance. Elk hunting is important to local communities in the same way wolf hunting is: it draws visitors and strengthens businesses (Robbins 2006).

Benefiting Local Communities: Tourism

Wildlife tourism is a multi-billion-dollar industry that employs millions of people all over the world (Higginbottom 2004). Wildlife tourism also contributes to wildlife conservation both through monetary support and by instilling positive attitudes toward wildlife and the environment in the mind of the public (World Tourism Organization 2014). YNP is part of this enterprise because hundreds of thousands of people visit the park each year for the purpose of wildlife viewing. This increase in tourism is beneficial to the neighboring communities because it brings more people to the local businesses.

All of the tourism to the Yellowstone area combined brings over $543 million in economic benefits to the area and supports 6,662 jobs (Weaver 2015). Before the reintroduction, it was projected that the renewed presence of wolves would add $23 million annually to the economic benefit felt by the local area (Fritts et al. 1997). A study done a decade post-reintroduction found that the actual benefit was closer to $35 million a year (Duffield 2008). A large part of this economic benefit is likely due to the influx of tourists hoping to catch a glimpse of the gray wolf.

According to Higginbottom (2004), wildlife tourism is dependent on three components: the wildlife, tourists, and accommodating locals. Prior to the reintroduction of wolves in YNP, in terms of biodiversity, the wildlife component was weak. The increase in biodiversity that resulted from the reintroduction of wolves helped strengthen this component which, in turn, relayed economic benefits to the locals by drawing in more tourists. Wolves are described as an example of charismatic megafauna; they are large mammals with widespread popular appeal. In terms of tourism, YNP receives many tourist specialists, or people who participate in wildlife tourism in order to see a specific species, like wolves, or a group of species. In 2005, survey results showed that 44% of visitors to YNP listed wolves as the species they wished to see or hear the most (Duffield 2008). Other specialists, like birdwatchers, may have visited the park more frequently after wolf reintroduction because of the increase in biodiversity. Higginbottom (2004) stated that specialists spend more money than generalists during a trip dedicated to wildlife tourism. Therefore, the increase in biodiversity and the reintroduction of wolves likely drew more specialists to the area and increased the total amount of tourist spending.

The local people can benefit both directly and indirectly from wildlife tourism in Yellowstone. One way direct benefits can arise is through employment with the National Park Service. In peak summer season, the National Park Service employs approximately 780 people in a large variety of positions including park rangers, tour guides, and maintenance personnel (National Park Service “Park Facts,”a2016). The larger fraction of the employees working in YNP work for outside vendors that are allowed to operate inside the park; this group makes up about 3,200 people (National Park Service “Park Facts,”a2016). There are also many jobs in the local communities that cater to the visitors to Yellowstone; these include restaurant, hotel, and other commercial employers like gift shops (Higginbottom 2004).
Higginbottom (2004) showed that if profits of wildlife tourism stay local, they improve access to health care, education, and food, and possibly help reduce poverty. Furthermore, if wildlife tourism is able to survive long-term, it can raise the standard of living for the host communities as well as diversify the economic base. The reintroduction of wolves brought back a key component of wildlife tourism in YNP and likely increased the longevity of the venture.

Preserving Culture

One of the Native American tribes that originally inhabited the American West is the Nez Perce tribe. Today the Nez Perce control a reservation in North Central Idaho that includes more than twenty communities and towns (Nez Perce Tribe “The Nez Perce Reservation and its Location,”h2016). According to Roesler (1995), Seven Drums, one of their traditional religions, maintains that a creator, known as Hanyawat, made Mother Earth and humans; Mother Earth then provided food to the people through plants and animals. According to the Nez Perce, everything has a soul, and there is a vital connection between nature and humans (Roesler 1995). Because of this, the loss and eventual reintroduction of wolves had a great spiritual effect on the tribe.
According to Cheater (1998), many in the Nez Perce tribe feel a special connection to their brethren the wolves because they share a similar history, rife with persecution. Starting in 1855, European Americans imposed a series of treaties on the Nez Perce forcing them to give up approximately 95% of their land. This, and other injustices, led to war between the Nez Perce and the United States in 1877 (Cheater 1998). At the same time, the European-American settlers in the west were waging war on the wolf. By the early 1930s, gray wolves had been almost completely eradicated from the lower 48 states (Cheater 1998). These parallels strengthen the connection to wolves felt by the Nez Perce people.

The absence of the wolf from the American West had a negative spiritual effect on the Nez Perce tribe. Levi Holt, a tribe elder, said, “In the time of the wolves´ absence, the tribe has suffered—a vital link in our sacred circle has been broken” (Cheater 1998). The reintroduction of the wolf allowed the tribe to renew its cultural ties to the wolf. Wilson (1999) asserted that a great uplift in spiritual and cultural values for the Nez Perce would result from having wolves back in the sacred places of their ancestors. According to Fritts et al. (1997), when the four wolves destined for Idaho arrived at the airport over two decades ago, two spiritual leaders from the Nez Perce tribe were there to greet them and they held a prayer ceremony to welcome their brothers home.
The Nez Perce tribe itself played a large part in the reintroduction of wolves to Idaho and their management since the reintroduction. One of the goals of the project was to promote education about wolves and Nez Perce culture. In 1996 a wolf education facility, managed by Levi Holt, was constructed on Nez Perce lands that aimed to do just that (Wilson 1999). The center cares for a pack of captive-raised wolves that serve as ambassadors for their species and garner conservation support. The center also provides visitors a chance to learn about Nez Perce history and culture, therefore helping to secure the future of the tribe (Wilson 1999).


Despite the importance of all species, a majority of the public are mostly interested in charismatic megafauna, such as wolves. An example of this comes from Jacobson et al. (2006) who showed that among United States citizens, 89% believed bald eagles should be protected whereas only 24% believed the endangered Kauai wolf spider deserves protection. Charismatic species also lead more people to support conservation programs than does the sole concept of saving ecosystems (Engels and Jacobson 2007). Wolves, as charismatic megafauna, have the power to spark people’s interest in conservation that can later be extended to all species and can eventually be applied to support environmental policies.

YNP has many programs for visitors to improve their knowledge and understanding about the natural world. One of those is the Expedition Yellowstone program (National Park Service 2016), a curriculum-based residential program that teaches students in the fourth through eighth grade and their instructors about the natural and cultural history of YNP through hands-on outdoor experiences. The presence of wolves adds to the authenticity of the experience; the ecosystem is whole once again. The wolf presence also offers a unique opportunity to discuss the basics of trophic cascades and the importance of wolves and every other native species in the ecosystem. Learning about wolves in this way can then produce more positive attitudes toward the environment in general.

Another program is the Yellowstone Association Institute, which offers courses for middle-school through college-aged groups. Courses in over 50 subject areas including wolves, wildlife biology, wildlife management, and climate change, are taught by experts in that field. The presence of wolves in Yellowstone informs many of the courses like those mentioned as well as other less obvious subjects like earth science, American Indian history and culture, and westward expansion. With wolves present once again, these courses become less academic and more authentic and applied; the need to discuss what would happen if wolves were present is no longer required. Now students can see firsthand the results of the renewed wolf presence. In addition to these programs held within the park, the wolf reintroduction to YNP can serve as an example of a successful reintroduction as well as a trophic cascade for students studying conservation and ecology all over the world.


My findings clearly show that the reintroduction of wolves to YNP helped achieve both the ecological and human-centered goals of the national park. Overall, the ecological goal of the national park is to maintain the health of the ecosystem, through high biodiversity, in order to increase the ecosystem’s resilience and ensure its survival. The reintroduction of wolves led to a trophic cascade that increased the biodiversity of woody species by controlling the elk population. It also increased the health of riparian zones, subsequently increasing the biodiversity of the birds and mammals that live there. Wolves may also act as a buffer against climate change, which in itself would help maintain the park’s biodiversity.
National parks such as Yellowstone serve the human population in three main ways. They economically support local communities, they help preserve culture, and they provide educational services. The wolves make YNP a healthier and more authentic ecosystem for all of the educational programs run within the park; the wolves can spark a love of nature in children and adults that can lead them to have better attitudes toward conservation measures. Lastly, the reintroduction of wolves gives a perfect illustration of a trophic cascade that can be used as an example for students all over the world to learn about wildlife and ecology.


American Trails. “Federal Land Management.” Accessed January 30, 2018.
Bangs EE and SH Fritts. 1996. “Reintroducing the Gray Wolf to Central Idaho and Yellowstone National Park.” Wildlife Society Bulletin 24: 402–413.
Baril, Lisa M. et al. 2011. “Songbird Response to Increased Willow (Salix spp.) Growth in Yellowstone’s Northern Range.” Ecological Applications 21: 2283–2296.
Barton, Melissa. 2005. “Restoration or Destruction: The Controversy over Wolf Reintroduction. Journal of Young Investigators.”
Berger, Joel et al. 2001. “A Mammalian Predator-Prey Imbalance: Grizzly Bear and Wolf Extinction Affect Avian Neotropical Migrants.” Ecological Applications 11: 947–960.
Beschta, RL. 2005. “Reduced Cottonwood Recruitment Following Extirpation of Wolves in Yellowstone’s Northern Range.” Ecology 86: 391–403.
Beschta, RL and W.J. Ripple. 2012. “Berry-Producing Shrub Characteristics Following Wolf Reintroduction in Yellowstone National Park.” Forest Ecology and Management 276: 132–138.
Beschta RL and W.J. Ripple. 2016. “Riparian vegetation recovery in Yellowstone: The first two decades after wolf reintroduction.” Biological Conservation 198: 93–103.
Blanco, Krystal et al. 2014. “Population Dynamics of Wolves and Coyotes at Yellowstone National Park: Modeling Interference Competition with an Infectious Disease.” [is this a website? Journal article?]
Bruscino, MT and TL Cleveland. 2004. “Compensation Programs in Wyoming for Livestock Depredation by Large Carnivores.” Sheep and Goat Research Journal 19: 47–49.
Byers, JE et al. 2006. “Using ecosystem engineers to restore ecological systems.” Trends in Ecology & Evolution 21: 493–500.
Camargo-Gamboa G, R. Huerta-Quintanilla R, and M. Rodríguez-Achach. 2010. “Ecological competition and the role of an apex predator.” Physica A: Statistical Mechanics and its Applications 389: 4075–4080.
Caron, Chad et al. 2016. “Native American’s Relationship with Wolves. Wild Wisconsin Wolves, Wisconsin, USA.”
Cheater, Mark. 1998. “Wolf Spirit Returns to Idaho.” National Wildlife Federation, Merrifield VA.
Costanza, R, BG Norton, and BD Haskell, eds. 1992. Ecosystem Health: New Goals for Environmental Management. Washington, D.C: Island Press.
Curtin, Susanna. 2009. “Wildlife Tourism: The Intangible, Psychological Benefits of Human–Wildlife Encounters.” Current Issues in Tourism 12: 451–474.
Curtis, Sam. 2002. “Making a Killing. Montana Outdoors, Helena, MT.”
Dallimer, Martin et al. 2012. “Biodiversity and the Feel-Good Factor: Understanding Associations between Self-Reported Human Well-being and Species Richness.” Bioscience 62: 47–55.
Duffield, John W. et al. 2008. “Wolf Recovery in Yellowstone: Park Visitor Attitudes, Expenditures, and Economic Impacts.” The George Wright Forum 25: 13–19.
Eberhardt LL, P.J. White, R.A. Garrott, and D.B. Houston. 2007. “A Seventy-Year History of Trends in Yellowstone’s Northern Elk Herd.” The Journal of Wildlife Management 71: 594–602.
Engels, CA and S.K. Jacobson. 2007. “Evaluating Long-Term Effects of the Golden Lion Tamarin Environmental Education Program in Brazil.” The Journal of Environmental Education 38: 3-14.
French, Brett. 2016. “Montana Hunters Killed Record Number of Elk in 2015.” Billings Gazette (Billings, MT).
Fritts, Steven H. et al. 1997. “Planning and Implementing a Reintroduction of Wolves to Yellowstone National Park and Central Idaho.” Restoration Ecology 5: 7–27.
Gamfeldt L, H. Hillebrand, and P.R. Jonsson. 2008. “Multiple Functions Increase the Importance of Biodiversity for Overall Ecosystem Functioning.” Ecology 89:1223–1231.
Garrott, Robert A. et al. 2005. “Generalizing Wolf Effects across the Greater Yellowstone Area: A Cautionary Note.” Wildlife Society Bulletin 33: 1245–1255.
Higginbottom, Karen, ed. 2005. “Wildlife Tourism: Impacts, Management, and Planning.” Australia: Common Ground Publishing.
Holling, CS. 1973. “Resilience and Stability of Ecological Systems.” Annual Review of Ecology and Systematics 4: 1–23.
Hollenbeck, JP and W.J. Ripple. 2008. “Aspen Snag Dynamics, Cavity-Nesting Birds, and Trophic Cascades in Yellowstone’s Northern Range.” Forest Ecology and Management 255: 1095–1103.
International Hunters Education Association 2016.

Front Page

Jacobson, Susan K. et al. 2006. Conservation Education and Outreach Techniques. New York: Oxford University Press.
Johnson, CN and J. VanDerWal. 2009. “Evidence That Dingoes Limit Abundance of a Mesopredator in Eastern Australian Forests.” Journal of Applied Ecology 46: 641–646.
Kellert, SR, M. Black, C.R. Rush, and A.J. Bath. 1996. “Human Culture and Large Carnivore Conservation in North America.” Conservation Biology 10: 977–990.
Khalil, Hussein et al. 2014. “The Relationship between Wolverine and Larger Predators, Lynx and Wolf, in a Historical Ecosystem Context.” Community Ecology 175: 625–637.
Lackey, RT. 2001. “Values, Policy, and Ecosystem Health Options for Resolving the Many Ecological Policy Issues we Face Depend on the Concept of Ecosystem Health, but Ecosystem Health is Based on Controversial, Value-Based Assumptions that Masquerade as Science.” BioScience 51: 437–443.
Leopold, Aldo. “Thinking Like a Mountain” Accessed October 2017.
Loreau M. et al. year. “Biodiversity and Ecosystem Functioning: Current Knowledge and Future Challenges.” Science 294: 804–808.
Louv, R. 2005. Last Child in the Woods: Saving our Children from Nature-Deficit Disorder. New York: Algonquin Books of Chapel Hill.
MacArthur, RH and E.R. Pianka. 1966. “On Optimal Use of a Patchy Environment.” The American Naturalist 100: 603–609.
Marris, E. 2001. Rambunctious Garden: Saving Nature in a Post-Wild World. New York: Bloomsbury USA.
McLaren, BE and R.O. Peterson. 1994. “Wolves, Moose, and Tree Rings on Isle Royale.” Science 266: 1555–1558.
Mech, LD. 1977. “Wolf-Pack Buffer Zones as Prey Reservoirs.” Science 198: 320–321.
Miller, Tyler G. and Scott Spoolman. 2007. Environmental Science: Problems, Concepts, and Solutions, 12th edition. Pacific Grove, CA: Brooks-Cole Publishing.
Mills, LS, M.E. Soulé, and D.F. Doak. 1993. “The Keystone-Species Concept in Ecology and Conservation.” BioScience 43: 219–224.
Montana Fish, Wildlife, and Parks. “Fishing Liscence and Permit Applications. Accessed January 30, 2018.
National Park Service. “Birth of a National Park. National Park Service, Wyoming, United States.” Accessed September 2016.
National Park Service. “Coyote. Yellowstone Media Group, Inc.” Accessed September 2016.
National Park Service. “Gray Wolf (Canis Lupus).” U.S. Fish and Wildlife Service, Washington DC. Accessed September 2016.
National Park Service. “Guidance for Protecting Yellowstone.” National Park Service, Wyoming, United States. Accessed September 2016.
National Park Service. “Historic Tribes.” Accessed September 2016.
National Park Service. “History.” Accessed September 2016.
National Park Service. “Mammals.” Accessed September 2016.
National Park Service. “National Park System: Caring for the American Legacy.” Accessed October 2016.
National Park Service. “The Nez Perce Reservation and its Location.” Accessed October 2016.
National Park Service. “Park Facts.” Accessed September 2016.
National Park Service. “Park History.” Accessed September 2016.
National Park Service. “Visitor Use Statistics.” Accessed October 2016.
National Park Service. “Where Does the Money for Conservation Come From?” Accessed October 2016.
National Park Service. “Wolf Management.” Accessed September 2016.
National Park Service. “Wolf Restoration.” Accessed September 2016.
O’Neill, Robert V. 2001. “Is It Time to Bury the Ecosystem Concept? (With Full Military Honors, of Course!).” Ecology 82: 3275–3284.
Ostfeld, RS and F. Keesing. 1999. “Biodiversity and Disease Risk: The Case of Lyme Disease.” Conservation Biology 14: 722–728.
Parker, Stephanie. “Ungulate Management in Yellowstone National Park.” National Academies, Washington, DC. Accessed September 2016.
Prugh, L.R. et al. 2009. “The Rise of the Mesopredator.” BioScience 59: 779–791.
Ripple, W.J., E.J. Larson, R.A. Renkin, D.W. Smith. 2001. “Trophic cascades among wolves, elk, and aspen on Yellowstone National Park’s northern range.” Biological Conservation 102: 227-234.
Ripple, W.J. and R.L. Beschta. 2003. “Wolf reintroduction, predation risk, and cottonwood recovery in Yellowstone National Park.” Forest Ecology and Management 184: 299–313.
Ripple, W.J. and R.L. Beschta. 2004. “Wolves and the Ecology of Fear: Can Predation Risk Structure Ecosystems?” BioScience 54: 755–766.
Ripple, W.J. and R.L. Beschta. 2012.“Trophic Cascades in Yellowstone: The First 15 Years After Wolf Reintroduction.” Biological Conservation 145: 205–213.
Ripple, W.J. and E.J. Larsen. 2000. “Historic Aspen Recruitment, Elk, and Wolves in Northern Yellowstone National Park, USA.” Biological Conservation 95: 361–370.
Robbins, P. 2006. “The Politics of Barstool Biology: Environmental Knowledge and Power in Greater Northern Yellowstone.” Geoforum 37: 185–199.
Roesler, Richard. 1995. “Praying to A Different Beat Group Of Nez Perce Reviving Tribe’s Native Beliefs; Not Everyone Pleased.” The Spokeman-Review, July 31, 1995.
Sala, E. 2006. “Top predators provide insurance against climate change.” Trends in Ecology & Evolution 21: 479–480.
Seddon, Philip J. et al. 2007. “Developing the Science of Reintroduction Biology.” Conservation Biology 21: 303–312.
Scheyvens, Regina. 1999. “Ecotourism and the Empowerment of Local Communities.” Tourism Management 20: 245–249.
Sikes, Derek S. 1994. “Influences of ungulate carcasses on Coleopteran communities in Yellowstone National Park, USA.” Master’s Thesis, Montana State University.
Smith, DW, R.O. Peterson RO, and D.B. Houston. 2003. “Yellowstone After Wolves.” BioScience 53: 330–340.
Stenseth, NC, W. Falck, O.N. Bjørnstad, and C.J. Krebs. 1997. “Population Regulation in Snowshoe Hare and Canadian Lynx: Asymmetric Food Web Configurations between Hare and Lynx.” Proceedings of the National Academy of Sciences of the United States of America 94: 5147–5152.
Switalski, TA. 2003. “Coyote Foraging Ecology and Vigilance in Response to Gray Wolf Reintroduction in Yellowstone National Park.” Canadian Journal of Zoology 81: 985–993.
Weaver, Traci. 2015. “Tourism to Yellowstone National Park Creates $543.7 Million in Economic Benefits.” National Park Service, Wyoming, United States.
Williams, CK. et al. 2002. “A Quantitative Summary of Attitudes toward Wolves and Their Reintroduction (1972-2000).” Wildlife Society Bulletin 30: 575–584.
Wilmers, CC et al. 2003. “Trophic facilitation by introduced top predators: grey wolf subsidies to scavengers in Yellowstone National Park.” Journal of Animal Ecology 72: 909–916.
Wilmers, CC et al. 2012. “Do trophic cascades affect the storage and flux of atmospheric carbon? An analysis of sea otters and kelp forests.” Frontiers in Ecology and the Environment 10: 409–415.
Wilmers, CC and W.M. Getz. 2005. “Gray Wolves as Climate Change Buffers in Yellowstone.” PLOS Biology 3: 571–576.
Wilson, EE and E.M. Wolkovich. 2011. “Scavenging: How Carnivores and Carrion Structure Communities.” Trends in Ecology & Evolution 26: 129–135.
Wilson, PI. 1999. “Wolves, Politics, and the Nez Perce: Wolf Recovery in Central Idaho and the Role of Native Tribes.” Natural Resources Journal 39: 543–564.
World Tourism Organization. 2014.

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