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47.4C: Ecological Restoration

  • Page ID
    • Boundless
    • Boundless
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    Learning Objectives
    • Explain the purpose of ecological restoration projects

    Conservation in Preserves

    Establishment of wildlife and ecosystem preserves is one of the key tools in conservation efforts. A preserve is an area of land set aside with varying degrees of protection for the organisms that exist within the boundaries of the preserve. Preserves can be effective in the short term for protecting both species and ecosystems, but they face challenges that scientists are still exploring in order to strengthen their viability as long-term solutions.

    Due to the way protected lands are allocated (they tend to contain less economically-valuable resources rather than being set aside specifically for at-risk species or ecosystems) and the way biodiversity is distributed, determining a target percentage of land or marine habitat that should be protected to maintain biodiversity levels is challenging. The IUCN (International Union for Conservation of Nature) World Parks Congress estimated that 11.5 percent of earth’s land surface was covered by preserves of various kinds in 2003. This area is greater than previous goals; however, it only represents 9 out of 14 recognized major biomes. Research has shown that 12 percent of all species live solely outside preserves; these percentages are much higher when only threatened species and high-quality preserves are considered.

    Limitations on Preserves

    Some of the limitations on preserves as conservation tools stem from preserve designs. Additionally, political and economic pressures typically make preserves smaller, never larger, so setting aside areas that are large enough is difficult. Climate change will create inevitable problems with the location of preserves. The species within them will migrate to higher latitudes as the habitat of the preserve becomes less favorable. Scientists are planning for the effects of global warming on future preserves and striving to predict the need for new preserves to accommodate anticipated changes to habitats. Some argue that conservation preserves reinforce the cultural perception that humans are separate from nature, can exist outside of it, and can only operate in ways that do damage to biodiversity. Creating preserves reduces the pressure on human activities outside the preserves to be sustainable and non-damaging to biodiversity.

    Habitat Restoration

    Habitat restoration holds considerable promise as a mechanism for restoring and maintaining biodiversity. Restoration ecology aims to return ecosystems to a more natural, pre-disturbance state. Of course, once a species has become extinct, its restoration is impossible. However, restoration can improve the biodiversity of degraded ecosystems.

    Reintroducing wolves, a top predator, to Yellowstone National Park in 1995 led to dramatic changes in the ecosystem that increased biodiversity. The wolves, which function to suppress elk and coyote populations, provide more-abundant resources to the guild of carrion (flesh) eaters. Reducing elk populations has allowed re-vegetation of riparian areas, which has increased the diversity of species in that habitat. Decreasing the coyote population increased the populations of species that were previously suppressed by this predator. The number of species of carrion eaters has increased because of the predatory activities of the wolves. In this habitat, the wolf is a keystone species: it is a species that is instrumental in maintaining diversity in an ecosystem. Removing a keystone species from an ecological community may cause a collapse in diversity. Similarly, restoring a keystone species can have dramatic effects. The results from the Yellowstone experiment suggest that restoring a keystone species can have the effect of restoring biodiversity in the community. Ecologists have argued for the identification of keystone species where possible and for focusing protection efforts on those species. It also makes sense to attempt to return them to their ecosystem if they have been removed.

    Figure \(\PageIndex{1}\): Yellowstone National Park restoration efforts: (a) The Gibbon wolf pack in Yellowstone National Park represents a keystone species. The reintroduction of wolves into Yellowstone National Park in 1995 led to a change in the grazing behavior of (b) elk. To avoid predation, the elk no longer grazed exposed stream and riverbeds, such as (c) the Lamar Riverbed in Yellowstone. This allowed willow and cottonwood seedlings to grow. The seedlings decreased erosion and provided shading to the creek, which improved fish habitat. A new colony of (d) beaver may also have benefited from the habitat change.

    Other large-scale restoration experiments underway involve dam removal. In the United States, since the mid-1980s, many aging dams are being considered for removal rather than replacement because of shifting beliefs about the ecological value of free-flowing rivers and because many dams no longer provide the benefit and functions that they did when they were first built. The measured benefits of dam removal include restoration of naturally-fluctuating water levels (the purpose of dams is frequently to reduce variation in river flows), which leads to increased fish diversity and improved water quality. In the Pacific Northwest, dam removal projects are expected to increase populations of salmon, which is considered a keystone species because it transports key nutrients to inland ecosystems during its annual spawning migrations. In other regions, such as the Atlantic coast, dam removal has allowed the return of spawning anadromous fish species (species that are born in fresh water, live most of their lives in salt water, and return to fresh water to spawn). Some of the largest dam removal projects have yet to occur or have happened too recently for the consequences to be measured. The large-scale ecological experiments that these removal projects constitute will provide valuable data for other dam projects slated either for removal or construction.

    Key Points

    • Ecological preserves, while effective in the short term, are not yet viable, long-term solutions.
    • Some of the limitations on preserves as conservation tools include preserve designs, political and economic pressures, and climate change.
    • Habitat restoration is a promising tool for restoring and maintaining biodiversity; restoration can improve the biodiversity of degraded ecosystems.

    Key Terms

    • biodiversity: the diversity (number and variety of species) of plant and animal life within a region
    • keystone species: a species that exerts a large, stabilizing influence throughout an ecological community, despite its relatively small numerical abundance
    • carrion: dead flesh; carcasses

    Contributions and Attributions

    This page titled 47.4C: Ecological Restoration is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Boundless.

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