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Cascade effect (ecology)

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Title: Cascade effect (ecology)  
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Subject: F-ratio, Trophic state index, Ecosystem of the North Pacific Subtropical Gyre, Landscape ecology, Landscape limnology
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Cascade effect (ecology)

An ecological cascade effect is a series of secondary tropical forests. When hunters cause local extinctions of top predators, the predators’ prey's population numbers increase, causing an overexploitation of a food resource and a cascade effect of species loss.[3]

Current example of cascade effect

One example of the cascade effect caused by the loss of a top predator has to do with sea otters (Enhydra lutris). Starting before the 17th century and not phased out until 1911 when an international treaty was signed to prevent their further exploitation, sea otters were hunted aggressively for their pelts, which caused a cascade effect through the kelp forest ecosystems along the Pacific Coast of North America.[4] One of the sea otters’ primary food sources is the sea urchin (Class: Echinoidea). When hunters caused sea otter populations to decline, an ecological release of sea urchin populations occurred. The sea urchins then overexploited their main food source, kelp, creating urchin barrens where no life exists. No longer having food to eat, the sea urchins populations became locally extinct as well. Also, since kelp forest ecosystems are homes to many other species, the loss of the kelp ultimately caused their extinction as well.[5] In conclusion, the loss of sea otters in local areas along the Pacific coast seems to have caused a cascade effect of secondary extinctions, continuing into the present day.

See also

References

  1. ^ Olsen, T.M. D.M. Lodge, G.M. Capelli, and R.J. Houlihan. 1991. studied the impact of an introduced crayfish species (Orchantes rusticus)on littoral congener, snails, and macrophytes. Canadian Journal of Fisheries and Aquatic Sciences 48:1853-1861
  2. ^ Leigh, E.G., S.J. Wright, E.A. Herre, and F.E. Putz. 1993. The decline of tree diversity on newly isolated tropical islands: A test of a null hypothesis and the implications. Evol. Ecol. 7:76-102.
  3. ^ Dirzo, R. and A. Miranda. 1991. Altered patterns of herbivory and diversity in the forest understory: A case study of the possible defaunation. In P.W. Price, T.M. Liwinsohn, G.W. Fernandes, and W.W. Benson (eds.), Plant-animal Interactions: Evolutionary Ecology in Tropical and Temperate Regions, pp. 273-287. Wiley, NY.
  4. ^ Estes, J.A., D.O. Duggins, and G.B. Rathbun. 1989. The ecology of extinctions in kelp forest communities. Conservation Biology 3:251-264
  5. ^ Dayton, P.K., M.J. Tegner, P.B. Edwards, and K.L. Riser. 1998. Sliding baselines, ghosts, and reduced expectations in kelp forest communities. Ecol. Appl.8:309-322
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