Amanda's Thoughts

Large Predator Restoration by Use of Corridors: The Right or Wrong Path for Wildlife and Humans?

May 24, 2010 at 7:22 pm 2 comments

By: Amanda Artz

Introduction
Evidence of human growth and urbanization can be seen through the impacts on virtually every species on planet earth. Effects of this growth and urbanization, such as “species decline, endangerment and extinction of enormous proportions, and widespread deterioration in the quality of air, water and soils – the basic resources on which all of life depends”, are causing sheer chaos in the natural world (Bennet pg 16 2003).  Possibly no species are more affected than the world’s large, carnivorous predators.  These animals are extremely important to the overall health and function of an ecosystem, but conservation and restoration of them and their habitat is a giant grey area that can be seen as a metaphor for balancing humans and nature.  We can no longer wait to address this growing environmental and ethical issue, and by establishing clear goals and outlooks we can ensure the future of these species and ecosystems along with the continuing growth and success of our own.

The Importance of Large Predators to Ecosystems
Ecosystem veracity is regularly dependent on the functional presence of large carnivores (Foreman 2004).  Predators are “keystone species”, or species whose loss would have widespread ecological effects on their entire ecosystem (Bennet 2003).  Because of this, they exert a controlling influence on species at lower trophic levels (such as prey, what their prey eats, etc.) called top-down regulation (Beschta 2009).  Studies have found that large carnivores are major regulators of prey species numbers—“the opposite of the once-upon-a-time ecological orthodoxy that saw them as unimportant” (Foreman 2004 pg. 120). The loss of large predators in an ecosystem can eventually lead to the rapid increase in population of wild ungulates which in turn greatly impacts plant communities (Beschta 2009). A successful ecosystem contains a natural system of checks and balances.  Without large carnivores keeping their prey level populations in check, the ecosystem would be an unbalanced, deteriorating entity.

Restoring Large Predators
Biodiversity is heavily impacted when ecosystems lack large carnivores.  Forests in the eastern United States are so overrun with white-tailed deer that the regeneration of these forests has been made virtually impossible due to the deer’s consumption of trees and herbs (Foreman 2004).   This complex array of problems has a very simple solution: restore large carnivores, such as wolves and mountain lions, to the ecosystem.  This would reduce white-tailed deer numbers, allowing the forest to return to more natural patterns of succession and species richness (Foreman 2004).  On certain Venezuelan islands, howler monkey populations have exploded to more than ten times their historic densities due to lack of large predators (such as jaguar, puma, and harpy eagle) (Foreman  2004).  The result is that only five or less tree species out of seventy reach the sapling stage, and although the mature trees are able to reproduce, their seeds and seedlings are eaten by herbivores (Foreman 2004).  If the current situation continues, most of the plant and animal species in this population will go extinct within one or two tree replacement cycles (Foreman 2004). Without the return of predators, these ecosystems are well on the path to devastation or disappearance.

The absence of large carnivores also has unfathomed effects on humans.  In parts of Sub-Saharan Africa, leopard and lion populations have been decimated, allowing an uncontrolled rise in the baboon population (Columbia Basin Bulletin 2009). Baboon packs are notorious for raiding crop fields, and in some cases children are now being kept home from school to guard family gardens from baboons (Columbia Basin Bulletin 2009).  In another example, the elimination of wolves in certain ranching towns has led to a significant increase in coyotes, a predator once kept in check by the wolves (Columbia Basin Bulletin 2009). The coyotes attack domestic sheep and pronghorn antelope, and attempts to control them have been incredibly expensive, costing hundreds of millions of dollars (Columbia Basin Bulletin 2009). These unforeseen economic impacts could be mitigated simply by the restoration of carnivorous predators.  Who knew that the absence of large predators could have such huge effects on the very species that removed them in the first place?

Perhaps the best example in which restoring large predators begins to heal damaged ecosystems is the reintroduction of wolves into Yellowstone.  Since elk populations lacked consistent predators after the elimination of wolves from the ecosystem (grizzly bears and mountain lions do prey on elk, but much less frequently), they became sluggish and careless, loafing in sizeable herds in river meadows (Foreman 2004).  Lack of large predators not only increased their numbers, but also changed their behaviors.  They overgrazed grasslands and willow shoots, an important food source of beavers, which in turn made the beaver populations decline sharply (Foreman 2004).  After reintroducing wolves into the Yellowstone ecosystem, elk behavior returned to a more natural state; beavers are beginning to re-establish themselves; and grasslands are no longer overgrazed and are harboring a more diverse mix of plant species (Foreman 2004).   The wolves’ return has virtually saved this once dying ecosystem, and this case should be used as a prime example of how important restoration of large carnivores is to the successful and prosperous function of an ecosystem.

The Importance of Corridors in Large Predator Restoration

It is obvious that large predators are important to an ecosystem, but restoring them isn’t as simple as one may think.  Large predators are wide ranging species in that they require a significant area of habitat in order to survive. A mountain lion’s home range often spans more than 100 square miles (“Mountain Lions”). A grizzly bear’s territory can range between 70 and 400 square miles (“Grizzly Bear”). A wolf pack’s territory may cover 20 to 120 square miles (Wydeven date unknown).  Requiring such a large amount of territory can create problems for predators, especially when their ranges are fragmented by human encroachment, which is only increasing with population increase and new development.  In the United States alone, “twenty-seven ecosystem types have declined by as much as 98 percent or more since Europeans settled North America” (Terris 1999).  And yet the same force that has caused such massive devastation to wildlife habitats might very well be the only force that can reverse the damage and aid species with their last chance of survival.  Unfortunately, this is easier said than done when in the context of large predator restoration.  Predators have a very different reputation than species such as penguins, bunnies, and pandas.  Because humans feel threatened by their presence, large carnivorous predators have been persecuted since humans evolved.

Finding the balance between preserving and restoring nature and growing and expanding the human empire is a constant challenge that in many instances has been addressed unsuccessfully, and with new restoration theories and techniques this balance is being tested once again. Wildlife corridors are now being implemented as a means of connecting fragmented populations.  “Corridors are used by species to migrate, breed, and feed, and are increasingly believed to be one of the most effective tools available today for the conservation of biological diversity, especially in urban areas (Scholtterbeck 2001).” This restoration method is causing much debate among humans by truly testing this wildlife/human equilibrium.

A corridor is defined as a linear habitat that connects two or more larger blocks of habitat (Noss 1998). Human growth has decreased habitat patch size and has made habitats more isolated from other patches.  Small, isolated habitat patches are not as successful as large, inter-connected patches and have a much higher extinction rate. Small populations are more sensitive to disturbance.  Movement between patches can be detrimental to large predator populations since large, undisturbed ranges are very rare. Less movement between patches creates less genetic diversity, creating unhealthy populations that experience higher rates of inbreeding and inbreeding depression (Ernest et al 2003).  Corridors are an attempt to restore the environment and a population to what it once was: a healthy collection of metapopulations not artificially fragmented by human development and activity.  Restoring ecosystems through corridors in theory helps decrease problems within populations by lowering extinction rates in the sense of the equilibrium theory, lessening demographic stochasticity, stemming inbreeding depression, and fulfilling an inherent need for movement (Simberloff 1992). The thought is that once movement corridors are restored, populations can once again interact, increase, and move at higher rates than before, benefiting their population, the surrounding ecosystem as a whole, and even the entire species.

Corridor Restoration Example
There are many examples of corridor restoration projects in effect today, but perhaps the most famous case is the Yellowstone to Yukon Corridor Conservation Initiative (Y2Y).   Y2Y is a Canadian and U.S. non-profit organization “that seeks to preserve and maintain the wildlife, native plants, wilderness and natural processes of the mountainous region from Yellowstone National Park to the Yukon Territory” (Cushman 2009). Y2Y stretches almost 2,000 linear miles from Wyoming to the Arctic circle, encompassing nearly half of a million square miles in area, including 11 national parks in two countries and a multitude of reserves, preserves, forest units, wilderness areas, state parks, and private lands (“Yellowstone to Yukon Conservation Initiative—About Us”).

(“Yellowstone-to-Yukon” 2010)
The Y2Y area is home to a myriad of predator species such as grizzly bear, lynx, wolf, cougar, and wolverine. Due to encroachment of human development on their natural habitats, these wide-range species are being forced to live in small, increasingly isolated pockets of wild habitat which drastically decreases their rate of survival (Cushman 2009).  By preserving and restoring corridors within this region, animals in the ecosystems of the Y2Y region are able to move between these human-isolated habitats, providing them with a much higher rate of long-term survival and fecundity (“Yellowstone to Yukon Conservation Initiative—About Us”).  Having such a large area of successful corridors and interacting populations is a giant victory to the world of conservation, and this project has since been acting as a benchmark case for corridor restoration.

Effects of Corridors on Wildlife Populations
Corridors provide many benefits to populations, and “an array of studies have demonstrated that habitat corridors can facilitate the movement of wildlife” (Laurance pg 4 date unknown).” Dispersal is important for population dynamics because it allows individuals to immigrate to new populations or to recolonize locally extinct populations, which can lead to increased genetic diversity (Laurance date unkown). “A fragmented landscape that is interconnected is more likely to support viable plant and animal populations and integral ecological processes, than a landscape that is comprised of only isolated fragments” (as cited by Laurance date unknown pg 2).  “Corridors assist animals to cross local barriers and to maintain local movements through environments that are ecologically inhospitable, assist species to maintain traditional migratory movements between different geographic areas, and allow species to recolonize habitats by increasing dispersal and immigration (Bennett 2003 pg 38).” With all of these positive effects, it’s hard not to support the implementation of corridors.  Perhaps Keith Hay of the Conservation Fund says it best: “Corridors hold more promise for the management of the diversity of life than any other management factor except stabilization of the human population.” (as cited by Plummer 1995).

Sometimes connecting populations can also create unforeseen negative effects.  In some cases, corridors can allow disease and exotic species to spread through a metapopulation easier than they could through isolated populations (Plummer 1995). Natural disasters such as fires can also travel to habitats more easily along corridors than to habitats that are isolated.  Also, “although corridors are known to increase genetic diversity among populations, they may also function to decrease it, because the migration among individual populations may end up genetically homogenizing the metapopulation as a whole” (Plummer 1995 pg 1).  Even so, there are no significant studies in which these outcomes surface, so their likelihood seems somewhat slim.

Some research has been done to prove the positive changes corridors can induce on large predator populations.  As stated earlier in this paper, large predators can have effects on animals of lower trophic levels, so when predator populations benefit, so too can prey populations.  One study done in Japer National Park in Alberta, Canada examined how corridor restoration through a golf course changes the distribution of wolves and their prey.  Before the restoration of the corridor, wolves avoided humans and traveled around the golf course, using the mountainside to connect valley-bottom habitat (Shepherd 2006). As a result, elk densities were highest in the golf course (Shepherd 2006). “After restoration, wolves shifted most of their movement to the golf course corridor, whereas elk dispersed along the corridor and mountainside” (Shepherd 2006 pg 5). When traveling through the study area, wolves chose areas with high prey abundance, low elevations, and low levels of human activity (Shepherd 2006).

(Shepherd 2006 pg 5)
Corridor restoration increased the area of high quality habitat available to wolves, increased their access to elk and deer at low elevations, and increased deer numbers.  These results corroborate other studies suggesting that wolves and elk quickly adapt to landscape changes and that corridor restoration can improve habitat quality and reduce habitat fragmentation (Shepherd 2006).  This study is a great example of the effectiveness of corridors on large predators and their prey.
Unfortunately, not enough studies have been done that show the after-effects of corridors on wildlife populations.  Establishing corridors is a fairly new restoration approach, and after implementation it can take some time before conclusive results are seen.  Hopefully with time more research will be conducted and results will be available to the public that show just how beneficial corridors are to wildlife, ecosystems, and humans.

Effects of Corridors on Human Populations
Although restoring corridors is mostly seen as having positive effects on wildlife, it can also have many positive effects on human populations.  There has been much interest in the use of corridors because they are seen as a visible solution to a visible problem (Bennet 2003). “Habitat corridors can be protected, managed, or restored at the level at which individuals or community groups are able to carry out conservation works. It is feasible for local communities to actually ‘do something about’ managing linkages in their local environment and to see visible environmental change as a result” (Bennet 2003 pg 5). Other environmental issues on a more global scale–such as climate change, population growth, loss of tropical forests, and desertification of arid lands–can seem outside the realm of individual or community action (Bennet 2003). Corridors allow communities to get involved in restoring their local environment and make them feel like they are truly making a difference.  Habitat corridors can also provide ecosystem services such as protecting watersheds and stream quality and providing windbreaks (Laurance date unknown). They also enhance property values and improve the overall quality of life by providing scenic, serine views of nature and open space (Tamasi date unknown).

Perhaps the most important benefit that corridors provide to humans is that they lessen dangerous encounters with predators.  When humans enter the territory of large predators, they are always taking a risk.  Last April, a young woman jogging in the foothills behind her house was stalked and pulled from the trail by a female mountain lion, who quickly mauled her to death (as cited by Cronon 1996).  Houses being built along hillsides have become a more common practice due to urban sprawl, and unfortunately they are often built adjacent to prime predator habitat.  If corridors were implemented in these areas, predators would have more options and thus would be more likely to avoid humans, staying farther away from them and their homes.  Corridors provide a safe passage for wildlife and while doing so make neighborhoods in or near predator habitat safer as well.  Although there are some arguments that implementing corridors can bear high economic costs (Simberloff 1992), I believe the pros outweigh the cons.

Once corridors are established, many people want to use them for recreational purposes like hiking.  This, of course, defeats one of the original purposes for the implementation of a corridor: to allow animals to move between populations AWAY from humans.  A study done on a Rio Grande trail that was closed to the public during the winter to protect wildlife used motion-sensor cameras that have since caught an immense array of wildlife (Frey 2010).  Having inaccessible wilderness areas is quite controversial to many, simply because people love wilderness when they are able to “experience it” for themselves.  But evidence that corridors are used more frequently once human activity decreases can’t be ignored. Humans must begin to understand that there are places appropriate for recreation and other places that are not (Frey 2010), and that we need to accept these trade-offs in order to successfully coexist with large predators.

Conclusions and Further Research
Corridors are a positive restoration strategy that can have many benefits to large predators as well as to other species in an ecosystem.  After doing my research, I believe we should definitely continue to pursue corridors as a method of conservation and restoration.  In doing so, certain things need to be considered when looking at the design and feasibility of such corridors. Suitable habitat for species should occur on both sides of and within the crossing structure (as cited by Beier et al 2008).  Appropriate vegetation cover and space should be present to encourage animal movement through the corridor.  Also, human activity should be managed near each crossing structure (Beier et al 2008).  Limiting the amount of foot traffic and human presence in corridors is important to ensure animals are not disturbed. Although there is plenty of research about how to implement corridors, case studies where corridors were successful are few and far between, making this restoration approach not as obviously desirable as I would have wished.

Humans must do more research on the effectiveness of corridors on wildlife populations.  It was difficult to find studies which recorded any type of positive or negative changes in an ecosystem.  Most studies stressed the importance of corridor implementation but had no hardcore, field-study related evidence to back up their claims.  The time to act is now: people need to stop throwing ideas around and wondering if something can work and instead, actually put some plans into action.  There is no way to tell if something will work unless we allow it to run its course and record and analyze the results.  The longer we wait to implement corridors, the more degraded predator populations will become, moving them closer to becoming endangered, or worse, extinct.  By restoring corridors now, we can ensure positive changes for predators in the future, by learning how effective corridors can be and by discovering the most effective ways to implement them.

Humans must change their views about large predators, and this can only be done through education.  Restoring them can be a delicate matter, especially if the populations in question are near recreational or residential areas.  People need to understand that predators don’t specifically prey on humans; when humans are attacked, it is because they are in the predators’ territory.  When pets or livestock are attacked, it is because the predator is naturally hunting a biologically appropriate animal that it views as its prey in its territory.  By choosing to live in areas that are known predator habitat, humans are choosing to live amongst predators and therefore must accept the responsibilities that come with living there.  If you live or are entering into predator habitat, you should never go hiking alone, always carry pepper spray, know what to do and how to act if you do encounter a predator, respect and conserve as much of their habitat as possible, never leave your pets unattended outdoors, and install predator-proof fencing around livestock. Developing a public education campaign to inform those living and working within the linkage area about living with wildlife, and the importance of maintaining ecological connectivity through corridors, is also a great way to get the public involved and on board with the project (Beier et al 2008).  By accepting these responsibilities, humans can finally learn to balance themselves with predators and successfully coexist together.

While doing research for this project, I was hit with my biggest conclusion of all that we have discussed previously in class:  Humans must redefine what we call “wilderness” and “wild”.  I believe humans see wild as something that we can’t control, which is one reason why so little wilderness is left.  Places that we consider most “wild” now are still completely controlled by human organizations such as the National Park Service, the Forest Service, or some other type of human manipulation.  Wilderness is essentially being tamed (Cronon 1995).  Healthy, successful ecosystems can only function to a certain point when under this level of control, as shown by the elimination of wolves in Yellowstone and the negative impacts that action had on the ecosystem there.  Only when we eliminate predators do we see nature as an acceptable place for humans to dominate. “Wilderness is more a state of mind than a fact of nature” (Cronon  1995 pg. 493), and we must fix this view if we wish to restore predators and the rest of the animals that directly or indirectly rely on their presence in an ecosystem.  Until we give predators the freedom to move in their own ranges by restoring corridors to their true wild potential, they will continue to struggle and decline.  In the words of Bill Cronon, “The time has come to rethink wilderness” (1995 pg 471).

Large predators need humans now more than ever before.  Although they once thrived separately from humans, their future now depends on the restoration and conservation efforts only we can provide.  Predators are an essential part of an ecosystem, and losing them for good would have dramatic, untold effects on virtually every species.  Restoring corridors might be one of the easiest methods of reversing predator decline, and although we don’t yet have an extensive body of research to prove how effective corridors can be, only through their implementation and analysis of the results will we have conclusive evidence.  “Connect our last parcels of wilderness, like pearls of a necklace, and mountain lions, bobcats, and wolves might once again roam their ancestral ranges” (Royte).

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