Student: Shiloh Psujek
Graduation date: May 2017
Type: Area of Interest (minor)
Date approved: November 2014
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Summary
Biomes are “complex, concrete geographical unit[s] of the landscape” (Walter et al. 1976) that make up the Earth, classified as either terrestrial (tundra, forest, desert, grassland) or aquatic (ocean, river, lake), based on the climate, animals, and plants found in the area. Each biome has various smaller ecosystems that make up the overall state of a biome. Within these ecosystems, different actors contribute to the biome’s total health and inner workings. One such important actor is the apex predator, defined as the predator that has no natural predators of its own.
Numerous apex predators play a significant role in maintaining the health and status of their ecosystem by affecting the population dynamics of prey species, and have been shown to influence and impact other species in their ecosystems (Finke et al. 2004). The removal and later reintroduction of the grey wolf (Canis lupus) to Yellowstone National Park is a commonly cited example of this effect: “As a major predator of large ungulates, grey wolves may suppress prey levels or alter prey behaviour to the extent that they affect vegetation patterns and productivity” (Wilmers et al. 2003). Within their respective biomes, key apex predators—such as wolves, Tasmanian devils, sharks, and orcas—play roles in a balancing act that their ecosystems use to maintain stability. Despite their critical role, there have been numerous occasions when an apex predator’s numbers were threatened, decreased, and even wiped out due to human intervention via hunting, fishing, or developing the surrounding areas. These insults led to environmental changes that affected disparate populations, not only that of the ecosystem’s apex predator: “[N]umbers of red deer and of wolves correlated negatively with wolf density…wolves can affect the mortality rates and conceivably the actual densities of their prey…” (Musiani et al. 2004). When this happens, the delicate balance in an ecosystem becomes skewed, which can lead to trophic cascades that can have devastating effects on both the ecosystem and its members, as well as the biome of which the ecosystem is a part (Pace et al. 1999).
To combat the decreasing numbers of apex predators in ecosystems, people elected to enact various conservation efforts and policies. These ranged from putting a cap on the number of animals killed during certain seasons, to reintroducing members of a species to the ecosystem in order to bolster numbers and encourage reproduction. Sometimes these efforts and policies worked, and sometimes they failed miserably. Oftentimes we only learn two extreme positions about this conservation need—yet the fact of the matter is, there are multiple facets to these issues that need consideration before anyone can pass judgement and make decisions that affect apex predator populations.
Another significant conservation issue arises with people who are directly affected by apex predators (e.g., ranchers, fishermen). Often, the livelihoods of these people are not taken into deep consideration when developing a conservation policy, a problem we must address if we are to improve our efforts whereby they do the least harm to the most people. The bigger issue at hand, however, is the lack of understanding of population ecology in regards to conservation efforts: “[M]ost conservation laws, including the ESA [Endangered Species Act], fail to reflect the effects of widespread ecological disappearances of strongly interacting species and the resulting ecosystem perturbations” (Soulé et al. 2005).
References
Finke, D. L., and R. F. Denno. “Predator Diversity Dampens Trophic Cascades.” NATURE 429 (6990): 407-410. DOI: 10.1038/nature02554
Musiani, Marco, and Paul C. Paquet. 2004. “The Practices of Wolf Persecution, Protection, and Restoration in Canada and the United States.” BioScience 54 (1): 50-60. DOI: 10.1641/0006-3568(2004)054[0050:TPOWPP]2.0.CO;2
Pace, Michael L., Jonathan J. Cole, Stephen R. Carpenter, and James F. Kitchell. 1999. “Trophic Cascades Revealed in Diverse Ecosystems.” Trends in Ecology and Evolution 14 (12): 483-488. DOI: 10.1016/S0169-5347(99)01723-1
Soulé, Michael E., James A. Estes, Brian Miller, and Douglas L. Honnold. 2005. “Strongly Interacting Species: Conservation Policy, Management, and Ethics.” BioScience 55 (2): 168-176.
Walter, Heinrich, and Elgene Box. 1976. “Global Classification of Natural Terrestrial Ecosystems.” Vegetatio 32 (2): 75-81.
Wilmers, Christopher C., Robert L. Crabtree, Kerry M. Murphy, and Wayne M. Getz. 2003. “Trophic Facilitation by Introduced Top Predators: Grey Wolf Subsidies to Scavengers in Yellowstone National Park.” Journal of Animal Ecology 72 (6): 909-916. DOI: 10.1046/j.1365-2656.2003.00766.x
Questions
- Descriptive (What is going on?): What do apex predators contribute to an environment? What are the extant policies regarding conservation of apex predators? What do trophic cascades do to an ecosystem?
- Explanatory (Why is this happening?): What constitutes an ecosystem failure? Why are conservation efforts not succeeding or not in place for failing ecosystems? How are biomes negatively affected by humans?
- Evaluative (So what? To what extent is this a problem?): How would trophic cascades affect the planet? What influence does being close to, or far from, an urban area have on species population levels and dynamics? Would we be able to survive if trophic cascades affected all biomes, terrestrial and aquatic?
- Instrumental (What can be done?): How can we protect apex predators while simultaneously appeasing those who are negatively affected by their existence? What more do we need to learn and educate ourselves about in order to make accurate and innovative decisions regarding apex predators and trophic cascades? How can we secure and maintain biome health?
Arts and humanities courses
- HIST 261 (Global Environmental History, 4 credits). Pre-approved A&H course; no justification required.
- PHIL 215 (Philosophy and the Environment, 4 credits). Pre-approved A&H course; no justification required.