![]() The exciting news, however, is that reestablishing top predators could help restore entire ecosystems. The evidence is “compelling” and the conclusions “inescapable”: similar, undesirable ecological conditions in each of the parks can be traced to the absence of keystone predator(s). He loss of recruitment occurred despite long-term variations in winter weather, snowpack, and other climate variables, with or without the occurrence of fire, and independent of efforts by the to control ungulate numbers inside the park (pre-1968) or to let them increase by ceasing control efforts (post-1968). Other environmental factors were excluded as possible causes: This hiatus in recruitment of woody species is also directly linked to the loss of beaver and the decline in food availability for other faunal species. He extirpation of the gray wolf – a keystone predator in this ecosystem – is most likely the overriding cause of the precipitous decline and cessation in the recruitment of aspen, cottonwood, and willow across the northern range. Two of the principal research scientists, Oregon State University ecologist William Ripple and forest hydrologist Robert Beschta, summarize (2005: 764) the unraveling of the northern ranges of Yellowstone National Park: The disappearance of top predators triggered an explosion of smaller “mesopredators,” such as coyotes, which led to further cascading effects.Loss of berry-producing shrubs, and young aspens and cottonwoods, led to changes in the diversity and abundance – and sometimes the outright loss – of other species, including beaver, amphibians, and songbirds.Long-term loss of streamside vegetation caused major changes in channel morphology and floodplain function.As a consequence, “recruitment” of cottonwood and aspen (i.e., the growth of seedling/sprouts into tall saplings and trees) was drastically reduced, and uncommon plants became rare or were disappeared completely. ![]() These animals over-browsed preferred plants, especially deciduous trees and shrubs like cottonwood, aspen, willow, and oaks, and spent more time in riparian areas.Large herbivores, such as elk or deer, increased in number and foraging behavior changed significantly.In each study area the long absence of wolves or cougars resulted in a similar “cascade” of effects: Similar findings from Olympic National Park will be published later this summer. Trophic cascades involving wolves or cougars have now been demonstrated in national parks in five different North American ecosystems – Yellowstone, Yosemite, Wind Cave, Jasper (in Alberta), and Zion. In the past ten years, field studies supporting this conclusion have appeared in leading journals and been reported by the National Research Council. There is “increasing evidence that the absence of large carnivores can initiate cascading perturbations through the trophic webs.” (Soulé and Terborgh, 1999:). (A Sand County Almanac 1949)Ī consensus is growing: “Questions about trophic cascades have shifted from whether to when, where and how often.” (Pace et al. I have seen every edible tree defoliated to the height of a saddle horn. I have seen every edible bush and seedling browsed, first to anemic desuetude, and then to death. I have watched the face of many a new wolfless mountain, and seen the south-facing slopes wrinkle with a maze of new deer trails. I have lived to see state after state extirpate its wolves. Trophic cascade theory can be traced to Aldo Leopold’s observations more than 60 years ago in the Southwest: “Trophic” is defined as “the food relationship of different organisms in a food chain.” The term for this phenomenon is a “trophic cascade,” defined as the “progression of indirect effects by predators across successively lower trophic levels.” (Estes et al., Encyclopedia of Biodiversity, 2001). The scientific evidence is that ecosystems unravel when wolves and other “keystone” predators are removed. Wolf advocates romanticize them as symbols of the wild.īut if we prize our dogs in part because of how useful they are – for herding, guarding, retrieving, guiding, and so forth – then our view of wolves must change. Like nearly all animals other than pets, wolves have been “objectified.” They have been “objects of scientific inquiry” and “objects of interest to people bound up in the natural world with them,” as well as “objects of hatred for livestock raisers.” (Barry Lopez, Of Wolves and Men, 2004: 203). The suggestion probably seems ridiculous, considering “wolves were hunted and killed with more passion and zeal than any other animal in U.S. Laramie – Could anyone be unfamiliar with the expression “Man’s best friend?”īut does everyone know that the beloved household dog is descended from wolves? Indeed, recent genetics research suggests that all domestic dogs originated from wolves in East Asia about 15,000 years ago.
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