Ever Here of These?<\/h3>\nWhat are Trophic Cascades?<\/strong><\/h2>\nTrophic (pronounced with the long oh sound) cascades occur when predators in a food web suppress the abundance or alter the behavior of their prey, thereby releasing the next lower trophic level from predation. That in turn affects lower trophic levels. The video takes a look at what has happened in Yellowstone National Park when the top predators, in this case wolves, are successfully reintroduced<\/em><\/strong> into an ecosystem. The results seem to have been astounding. Aldo Leopold is generally credited with first describing the mechanism of a trophic cascade, based on his observations of overgrazing of mountain slopes by deer after human extermination of wolves….<\/p>\nI urge everyone to click here<\/a> and watch the 4 minute, 33 second video. I have watched it several times and you will probably wind up doing the same thing. The quality of the video clips is pretty much so-so but the narration by George Monbiot is first rate: the guy gas a great voice. But it is the message that steals the show…. <\/p>\nThe video appears to have been done under the auspices of an organization named Sustainable Man. I did some web surfing and wound up at the Sustainable Human website here<\/a>. It has the same logo that appears at beginning of the video but then things get a bit mysterious. The website is quite interesting. If I am understanding correctly the guy running it and the blog is the son of a former mayor of San Francisco, Art Agnos. I could not find any connection to or mention of the “How Wolves Change Rivers” video. Christopher James Herman Agnos’s Life Resume, is however, quite an interesting read. You can find it here.<\/a><\/p>\nI searched around a bit more on the web and found some interesting stuff on Wikipedia here<\/a>. The entry there includes this:<\/p>\nThe gray wolf, after being extirpated in the 1920s and absent for 70 years, was reintroduced to the Park in 1995 and 1996. Since then a three-tiered trophic cascade has been reestablished involving wolves, elk (Cervus elaphus), and woody browse species such as aspen (Populus tremuloides), cottonwoods (Populus spp.), and willows (Salix spp.). Mechanisms likely include actual wolf predation of elk, which reduces their numbers, and the threat of predation, which alters elk behavior and feeding habits, resulting in these plant species being released from intensive browsing pressure. Subsequently, their survival and recruitment rates have significantly increased in some places within Yellowstone’s northern range. This effect is particularly noted among the range’s riparian plant communities, with upland communities only recently beginning to show similar signs of recovery.<\/em> See the video!<\/p>\nThe WyoFile site here<\/a> included this useful material in an excellent article by Deb Donahue:<\/p>\nThe scientific evidence is that ecosystems unravel when wolves and other \u201ckeystone\u201d predators are removed.<\/p>\nThe term for this phenomenon is a \u201ctrophic cascade,\u201d defined as the \u201cprogression of indirect effects [caused] by predators across successively lower trophic levels.\u201d (Estes et al., Encyclopedia of Biodiversity, 2001). \u201cTrophic\u201d is defined as \u201cthe food relationship of different organisms in a food chain.\u201d<\/p>\n
Trophic cascade theory can be traced to Aldo Leopold\u2019s observations more than 60 years ago in the Southwest:<\/p>\n
I have lived to see state after state extirpate its wolves. 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 seen every edible bush and seedling browsed, first to anemic desuetude, and then to death. I have seen every edible tree defoliated to the height of a saddle horn. (A Sand County Almanac 1949)<\/p>\n
A consensus is growing: \u201cQuestions about trophic cascades have shifted from whether to when, where and how often.\u201d (Pace et al. 1999). There is \u201cincreasing evidence that the absence of large carnivores can initiate cascading perturbations through the trophic webs.\u201d (Soul\u00e9 and Terborgh, 1999:). In the past ten years, field studies supporting this conclusion have appeared in leading journals and been reported by the National Research Council.<\/p>\n
Trophic cascades involving wolves or cougars have now been demonstrated in national parks in five different North American ecosystems \u2013 Yellowstone, Yosemite, Wind Cave, Jasper (in Alberta), and Zion. Similar findings from Olympic National Park will be published later this summer.<\/p>\n
In each study area the long absence of wolves or cougars resulted in a similar \u201ccascade\u201d of effects:<\/p>\n
\u2022 Large herbivores, such as elk or deer, increased in number and foraging behavior changed significantly.
\n\u2022 These animals over-browsed preferred plants, especially deciduous trees and shrubs like cottonwood, aspen, willow, and oaks, and spent more time in riparian areas.
\n\u2022 As a consequence, \u201crecruitment\u201d 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.
\n\u2022 Long-term loss of streamside vegetation caused major changes in channel morphology and floodplain function.
\n\u2022 Loss of berry-producing shrubs, and young aspens and cottonwoods, led to changes in the diversity and abundance \u2013 and sometimes the outright loss \u2013 of other species, including beaver, amphibians, and songbirds.
\n\u2022 The disappearance of top predators triggered an explosion of smaller \u201cmesopredators,\u201d such as coyotes, which led to further cascading effects.<\/em><\/p>\n
Make the blog interactive and teach me something…<\/strong><\/h2>\nIf you get half as interested in learning about trophic cascades as I did, please feel free to share any insights. Please also let us know if you think that there any exaggerations in the video…<\/p>\n
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Trophic (pronounced with the long oh sound) cascades occur when predators in a food web suppress the abundance or alter the behavior of their prey, thereby releasing the next lower trophic level from predation. That in turn affects lower trophic levels. The video takes a look at what has happened in Yellowstone National Park when the top predators, in this case wolves, are successfully reintroduced<\/em><\/strong> into an ecosystem. The results seem to have been astounding. Aldo Leopold is generally credited with first describing the mechanism of a trophic cascade, based on his observations of overgrazing of mountain slopes by deer after human extermination of wolves….<\/p>\n I urge everyone to click here<\/a> and watch the 4 minute, 33 second video. I have watched it several times and you will probably wind up doing the same thing. The quality of the video clips is pretty much so-so but the narration by George Monbiot is first rate: the guy gas a great voice. But it is the message that steals the show…. <\/p>\n The video appears to have been done under the auspices of an organization named Sustainable Man. I did some web surfing and wound up at the Sustainable Human website here<\/a>. It has the same logo that appears at beginning of the video but then things get a bit mysterious. The website is quite interesting. If I am understanding correctly the guy running it and the blog is the son of a former mayor of San Francisco, Art Agnos. I could not find any connection to or mention of the “How Wolves Change Rivers” video. Christopher James Herman Agnos’s Life Resume, is however, quite an interesting read. You can find it here.<\/a><\/p>\n I searched around a bit more on the web and found some interesting stuff on Wikipedia here<\/a>. The entry there includes this:<\/p>\n The gray wolf, after being extirpated in the 1920s and absent for 70 years, was reintroduced to the Park in 1995 and 1996. Since then a three-tiered trophic cascade has been reestablished involving wolves, elk (Cervus elaphus), and woody browse species such as aspen (Populus tremuloides), cottonwoods (Populus spp.), and willows (Salix spp.). Mechanisms likely include actual wolf predation of elk, which reduces their numbers, and the threat of predation, which alters elk behavior and feeding habits, resulting in these plant species being released from intensive browsing pressure. Subsequently, their survival and recruitment rates have significantly increased in some places within Yellowstone’s northern range. This effect is particularly noted among the range’s riparian plant communities, with upland communities only recently beginning to show similar signs of recovery.<\/em> See the video!<\/p>\n The WyoFile site here<\/a> included this useful material in an excellent article by Deb Donahue:<\/p>\n The scientific evidence is that ecosystems unravel when wolves and other \u201ckeystone\u201d predators are removed.<\/p>\n The term for this phenomenon is a \u201ctrophic cascade,\u201d defined as the \u201cprogression of indirect effects [caused] by predators across successively lower trophic levels.\u201d (Estes et al., Encyclopedia of Biodiversity, 2001). \u201cTrophic\u201d is defined as \u201cthe food relationship of different organisms in a food chain.\u201d<\/p>\n Trophic cascade theory can be traced to Aldo Leopold\u2019s observations more than 60 years ago in the Southwest:<\/p>\n I have lived to see state after state extirpate its wolves. 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 seen every edible bush and seedling browsed, first to anemic desuetude, and then to death. I have seen every edible tree defoliated to the height of a saddle horn. (A Sand County Almanac 1949)<\/p>\n A consensus is growing: \u201cQuestions about trophic cascades have shifted from whether to when, where and how often.\u201d (Pace et al. 1999). There is \u201cincreasing evidence that the absence of large carnivores can initiate cascading perturbations through the trophic webs.\u201d (Soul\u00e9 and Terborgh, 1999:). In the past ten years, field studies supporting this conclusion have appeared in leading journals and been reported by the National Research Council.<\/p>\n Trophic cascades involving wolves or cougars have now been demonstrated in national parks in five different North American ecosystems \u2013 Yellowstone, Yosemite, Wind Cave, Jasper (in Alberta), and Zion. Similar findings from Olympic National Park will be published later this summer.<\/p>\n In each study area the long absence of wolves or cougars resulted in a similar \u201ccascade\u201d of effects:<\/p>\n \u2022 Large herbivores, such as elk or deer, increased in number and foraging behavior changed significantly. If you get half as interested in learning about trophic cascades as I did, please feel free to share any insights. Please also let us know if you think that there any exaggerations in the video…<\/p>\n Be sure to like and follow BAA on Facebook by clicking on the logo link upper right. Tanks a stack!<\/p>\n We want and need to keep providing you with the latest free information, photography and Photoshop lessons, and all manner of related information. Show your appreciation by making your purchases immediately after clicking on any of our B&H or Amazon Affiliate links in this blog post. Remember, B&H ain’t just photography! Click on the logo link above and check out the specials, or use the search box on the top left of the page for your general shopping pleasure. <\/p>\n B&H orders placed at this time will be processed after they reopen at 9:00 AM on Wednesday, October 7, 2015. They are currently closed for the Succos holiday. <\/p>\n Those who prefer to support BAA by shopping with Amazon may use this link: <\/p>\n
\n\u2022 These animals over-browsed preferred plants, especially deciduous trees and shrubs like cottonwood, aspen, willow, and oaks, and spent more time in riparian areas.
\n\u2022 As a consequence, \u201crecruitment\u201d 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.
\n\u2022 Long-term loss of streamside vegetation caused major changes in channel morphology and floodplain function.
\n\u2022 Loss of berry-producing shrubs, and young aspens and cottonwoods, led to changes in the diversity and abundance \u2013 and sometimes the outright loss \u2013 of other species, including beaver, amphibians, and songbirds.
\n\u2022 The disappearance of top predators triggered an explosion of smaller \u201cmesopredators,\u201d such as coyotes, which led to further cascading effects.<\/em><\/p>\nMake the blog interactive and teach me something…<\/strong><\/h2>\n
Facebook<\/h3>\n
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