Friday, July 15, 2011 2:16:17 AM
Decline of predatory species throws food chains out of whack, report says
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As predatory [and certain large herbivore] species dwindle, food chains are thrown out of balance. The loss of large animals such as wolves and sharks has far-reaching implications, a new study says.
http://www.washingtonpost.com/national/health-science/as-predatory-species-dwindle-food-chains-are-thrown-out-of-balance/2011/07/14/gIQA70HxEI_gallery.html
By Darryl Fears, Published: July 14[, 3022]
The decline of large predators such as big cats, wolves, sharks and giant whales may be “humankind’s most pervasive influence on the natural world,” causing prey animals to swell in population and throw food chains out of balance, a new report says.
Humans have touched off the world’s latest mass extinction, according to the report, published Thursday in the journal Science, and the consequences are being felt on land and in water systems as large predators vanish.
“Recent research suggests that the disappearance of these animals reverberates further than previously anticipated,” says the report, “Trophic Downgrading of Planet Earth [ http://www.sciencemag.org/content/333/6040/301.abstract ].” In addition to creating an overabundance of prey, the dwindling number of predators contributes to the spread of disease, wildfires and invasive species.
The decline of wolves in Yellowstone Park is cited as an example of what can happen. Elk and deer in the park once flourished on willow trees and saplings, threatening a crucial part of the forest on which other creatures rely.
The report also mentions the slaughter of lions and leopards by hunters and herders in parts of sub-Saharan Africa. As a result of the killings, disease-carrying olive baboons have thrived without their top predators and inched closer to food crops and people.
The decimation of sharks along the U.S. Atlantic Coast has allowed their main prey, the cow-nosed ray, to proliferate and dine heavily on the threatened Chesapeake Bay oyster.
A reduction of big herbivores such as buffalo and wildebeest in East Africa through hunting is also a problem, the report says. Their demise has led to increases in plants that fuel giant wildfires in the dry season.
Americans don’t have to visit federal parks or sub-Saharan Africa or plunge into seas to see the consequences, said Ellen K. Pikitch [ http://www.somas.stonybrook.edu/people/pikitch.html ], a co-author of the report and a professor at Stony Brook University in New York. Many experience the problem every day in their own back yards.
“People who live in North America know it’s hard to grow a garden because deer will eat it,” said Pikitch, a marine biologist. “The lack of wolf populations throughout North America has led to an expansion of the deer population.
“You may hate wolves. You might think they’re dangerous. But without them, the land changes,” Pikitch said. “Deer carry ticks. We humans become more susceptible to diseases such as Lyme disease.”
Wildlife advocates say efforts to protect one species of predator in the United States were set back when the Obama administration signed a bill in April that removed 1,300 wolves from the endangered species list in northern Rocky Mountain states. It was the first time Congress had taken a species off the endangered list. The law allows limited hunting of the animals to begin this summer.
Other studies have examined the collateral damage caused by the near-extinction of large predators and herbivores. But the report in Science is the first to tie together the impact on land animals as well as salt and freshwater marine life, Pikitch said. It was conducted by an international team of 24 scientists and funded primarily by the Institute for Ocean Conservation Science at Stony Brook.
Much of the science in this area of study has focused on the threat to life at the bottom of the food chain, theorizing that small animals and plants are important because so many creatures rely on their survival.
Although “bottom-up” research is fundamental and important, the report says, “top-down” research deserves wider consideration “if there is to be any real hope for understanding and managing the workings of nature.”
The report acknowledges that top-down research of the food chain is difficult to conduct, noting that it can take decades to measure the effects of the disappearance of large predators.
“The irony .?.?. is that we often cannot unequivocally see the effect of large apex consumers until after they have been lost” and the ability to restore the species has also been lost, the report says.
Large predators, or apex species, include animals that people adore, such as otters, and others not so popular, such as vultures.
On the Pacific Coast, from Alaska to the southern tip of California, sea otters were hunted in the 1900s to near-extinction for their pelts. Their absence started a chain of events that nearly eliminated the kelp forests that nurture all manner of marine life on the coast.
Sea otters feed on sea urchins, which dine on kelp. Without otters, the sea urchin population exploded. The kelp forest started to disappear. When sea otter populations elsewhere were re-introduced to a few areas along the coast, the kelp started to rebound.
A telling consequences of the absence of large predators can be found on the Scottish island of Rum, where wolves have been gone for more than 250 years and red deer thrive, the report says. The once forested island is now treeless.
© 2011 The Washington Post
http://www.washingtonpost.com/national/health-science/decline-of-predators-such-as-wolves-throws-food-chains-out-of-whack-report-says/2011/07/14/gIQAaeY1EI_story.html [with comments]
===
Loss of large predators, top consumers disrupts ecosystems
The large predators include lions, wolves, killer whales and sharks.
July 14, 2011
The decline of large predators and other "apex consumers" at the top of the food chain has disrupted ecosystems all over the planet, an international team of scientists reports tomorrow (July 15) in Science [ http://www.sciencemag.org/content/333/6040/301.abstract ].
The study reviewed research on a wide range of terrestrial, freshwater and marine ecosystems and concluded that "the loss of apex consumers is arguably humankind's most pervasive influence on the natural world."
The “top down” ecological effects of losing these large animals have been underestimated compared to the “bottom up” effects of environmental changes, said Distinguished Professor of Biology Tom Schoener of the UC Davis Department of Evolution and Ecology, one of the authors of the review. The lead author is James Estes, professor of ecology and evolutionary biology at UC Santa Cruz.
“There are enormous implications for all aspects of ecology, from species diversity to effects on the air, water and soil, to the emergence of human diseases and the prevalence of wildfires,” Schoener said.
The decline of apex consumers has been most pronounced among the big predators, such as wolves and lions on land, killer whales and sharks in the oceans, and large fish in freshwater ecosystems. But dramatic declines have also occurred in populations of large herbivores, such as elephants and bison. These big animals are essentially invulnerable to predators — except for humans.
Apex consumers are also difficult to study and not amenable to the laboratory experiments that have guided a lot of thinking in ecology. But accumulating evidence from the field shows that the loss of apex consumers from an ecosystem triggers an ecological phenomenon known as a "trophic cascade," a chain of effects moving down through lower levels of the food chain.
Estes, Schoener and their co-authors cite several examples in their review, including:
•The destruction of wolves in Yellowstone National Park led to over-browsing of aspen and willows by elk, and restoration of wolves has allowed the vegetation to recover.
•The reduction of lions and leopards in parts of Africa has led to population outbreaks and changes in behavior of olive baboons, increasing their contact with people and causing higher rates of intestinal parasites in both people and baboons.
•A rinderpest virus epidemic decimated the populations of wildebeest and other ungulates (hooved animals) in the Serengeti, resulting in more woody vegetation and increased frequency and size of wildfires, before the virus was eradicated in the 1960s.
•Dramatic changes in coastal ecosystems have followed the collapse and recovery of sea otter populations; sea otters maintain coastal kelp forests by controlling populations of kelp-grazing sea urchins.
•The decimation of sharks in an estuarine ecosystem caused an outbreak of cow-nosed rays and the collapse of shellfish populations on which the rays feed.
Despite these and other well-known examples, the extent to which ecosystems are shaped by such interactions has not been widely appreciated.
"There's been a tendency to see it as idiosyncratic and specific to particular species and ecosystems," Estes said.
For example, Schoener points out that some ecologists have viewed trophic cascades as an issue largely for ocean systems, but the review discusses many examples from land.
Schoener’s own work has looked at the impact of a small predator, although large in its own world — lizards on small islands. He has found, for example, that removing the lizards from an island ecosystem can lead to increased damage to plants, because insects that eat the plants (and would normally be eaten by the lizards) multiply.
The review’s findings have profound implications for conservation. "To the extent that conservation aims toward restoring functional ecosystems, the re-establishment of large animals and their ecological effects is fundamental," Estes said. "This has huge implications for the scale at which conservation can be done. You can't restore large apex consumers on an acre of land. These animals roam over large areas, so it's going to require large-scale approaches."
The paper's co-authors include 24 scientists from institutions in six countries. Support for the study was provided by the Institute for Ocean Conservation Science, Defenders of Wildlife, White Oak Plantation, U.S. National Science Foundation, NSERC Canada and NordForsk.
About UC Davis
For more than 100 years, UC Davis has engaged in teaching, research and public service that matter to California and transform the world. Located close to the state capital, UC Davis has more than 32,000 students, more than 2,500 faculty and more than 21,000 staff, an annual research budget that exceeds $678 million, a comprehensive health system and 13 specialized research centers. The university offers interdisciplinary graduate study and more than 100 undergraduate majors in four colleges — Agricultural and Environmental Sciences, Biological Sciences, Engineering, and Letters and Science. It also houses six professional schools — Education, Law, Management, Medicine, Veterinary Medicine and the Betty Irene Moore School of Nursing.
Media contact(s):
•Tom Schoener, Evolution and Ecology, (530) 752-8319, twschoener@ucdavis.edu
•Andy Fell, UC Davis News Service, (530) 752-4533, ahfell@ucdavis.edu
Copyright © The Regents of the University of California, Davis campus
http://www.news.ucdavis.edu/search/news_detail.lasso?id=9942
View Photo Gallery
As predatory [and certain large herbivore] species dwindle, food chains are thrown out of balance. The loss of large animals such as wolves and sharks has far-reaching implications, a new study says.
http://www.washingtonpost.com/national/health-science/as-predatory-species-dwindle-food-chains-are-thrown-out-of-balance/2011/07/14/gIQA70HxEI_gallery.html
By Darryl Fears, Published: July 14[, 3022]
The decline of large predators such as big cats, wolves, sharks and giant whales may be “humankind’s most pervasive influence on the natural world,” causing prey animals to swell in population and throw food chains out of balance, a new report says.
Humans have touched off the world’s latest mass extinction, according to the report, published Thursday in the journal Science, and the consequences are being felt on land and in water systems as large predators vanish.
“Recent research suggests that the disappearance of these animals reverberates further than previously anticipated,” says the report, “Trophic Downgrading of Planet Earth [ http://www.sciencemag.org/content/333/6040/301.abstract ].” In addition to creating an overabundance of prey, the dwindling number of predators contributes to the spread of disease, wildfires and invasive species.
The decline of wolves in Yellowstone Park is cited as an example of what can happen. Elk and deer in the park once flourished on willow trees and saplings, threatening a crucial part of the forest on which other creatures rely.
The report also mentions the slaughter of lions and leopards by hunters and herders in parts of sub-Saharan Africa. As a result of the killings, disease-carrying olive baboons have thrived without their top predators and inched closer to food crops and people.
The decimation of sharks along the U.S. Atlantic Coast has allowed their main prey, the cow-nosed ray, to proliferate and dine heavily on the threatened Chesapeake Bay oyster.
A reduction of big herbivores such as buffalo and wildebeest in East Africa through hunting is also a problem, the report says. Their demise has led to increases in plants that fuel giant wildfires in the dry season.
Americans don’t have to visit federal parks or sub-Saharan Africa or plunge into seas to see the consequences, said Ellen K. Pikitch [ http://www.somas.stonybrook.edu/people/pikitch.html ], a co-author of the report and a professor at Stony Brook University in New York. Many experience the problem every day in their own back yards.
“People who live in North America know it’s hard to grow a garden because deer will eat it,” said Pikitch, a marine biologist. “The lack of wolf populations throughout North America has led to an expansion of the deer population.
“You may hate wolves. You might think they’re dangerous. But without them, the land changes,” Pikitch said. “Deer carry ticks. We humans become more susceptible to diseases such as Lyme disease.”
Wildlife advocates say efforts to protect one species of predator in the United States were set back when the Obama administration signed a bill in April that removed 1,300 wolves from the endangered species list in northern Rocky Mountain states. It was the first time Congress had taken a species off the endangered list. The law allows limited hunting of the animals to begin this summer.
Other studies have examined the collateral damage caused by the near-extinction of large predators and herbivores. But the report in Science is the first to tie together the impact on land animals as well as salt and freshwater marine life, Pikitch said. It was conducted by an international team of 24 scientists and funded primarily by the Institute for Ocean Conservation Science at Stony Brook.
Much of the science in this area of study has focused on the threat to life at the bottom of the food chain, theorizing that small animals and plants are important because so many creatures rely on their survival.
Although “bottom-up” research is fundamental and important, the report says, “top-down” research deserves wider consideration “if there is to be any real hope for understanding and managing the workings of nature.”
The report acknowledges that top-down research of the food chain is difficult to conduct, noting that it can take decades to measure the effects of the disappearance of large predators.
“The irony .?.?. is that we often cannot unequivocally see the effect of large apex consumers until after they have been lost” and the ability to restore the species has also been lost, the report says.
Large predators, or apex species, include animals that people adore, such as otters, and others not so popular, such as vultures.
On the Pacific Coast, from Alaska to the southern tip of California, sea otters were hunted in the 1900s to near-extinction for their pelts. Their absence started a chain of events that nearly eliminated the kelp forests that nurture all manner of marine life on the coast.
Sea otters feed on sea urchins, which dine on kelp. Without otters, the sea urchin population exploded. The kelp forest started to disappear. When sea otter populations elsewhere were re-introduced to a few areas along the coast, the kelp started to rebound.
A telling consequences of the absence of large predators can be found on the Scottish island of Rum, where wolves have been gone for more than 250 years and red deer thrive, the report says. The once forested island is now treeless.
© 2011 The Washington Post
http://www.washingtonpost.com/national/health-science/decline-of-predators-such-as-wolves-throws-food-chains-out-of-whack-report-says/2011/07/14/gIQAaeY1EI_story.html [with comments]
===
Loss of large predators, top consumers disrupts ecosystems
The large predators include lions, wolves, killer whales and sharks.
July 14, 2011
The decline of large predators and other "apex consumers" at the top of the food chain has disrupted ecosystems all over the planet, an international team of scientists reports tomorrow (July 15) in Science [ http://www.sciencemag.org/content/333/6040/301.abstract ].
The study reviewed research on a wide range of terrestrial, freshwater and marine ecosystems and concluded that "the loss of apex consumers is arguably humankind's most pervasive influence on the natural world."
The “top down” ecological effects of losing these large animals have been underestimated compared to the “bottom up” effects of environmental changes, said Distinguished Professor of Biology Tom Schoener of the UC Davis Department of Evolution and Ecology, one of the authors of the review. The lead author is James Estes, professor of ecology and evolutionary biology at UC Santa Cruz.
“There are enormous implications for all aspects of ecology, from species diversity to effects on the air, water and soil, to the emergence of human diseases and the prevalence of wildfires,” Schoener said.
The decline of apex consumers has been most pronounced among the big predators, such as wolves and lions on land, killer whales and sharks in the oceans, and large fish in freshwater ecosystems. But dramatic declines have also occurred in populations of large herbivores, such as elephants and bison. These big animals are essentially invulnerable to predators — except for humans.
Apex consumers are also difficult to study and not amenable to the laboratory experiments that have guided a lot of thinking in ecology. But accumulating evidence from the field shows that the loss of apex consumers from an ecosystem triggers an ecological phenomenon known as a "trophic cascade," a chain of effects moving down through lower levels of the food chain.
Estes, Schoener and their co-authors cite several examples in their review, including:
•The destruction of wolves in Yellowstone National Park led to over-browsing of aspen and willows by elk, and restoration of wolves has allowed the vegetation to recover.
•The reduction of lions and leopards in parts of Africa has led to population outbreaks and changes in behavior of olive baboons, increasing their contact with people and causing higher rates of intestinal parasites in both people and baboons.
•A rinderpest virus epidemic decimated the populations of wildebeest and other ungulates (hooved animals) in the Serengeti, resulting in more woody vegetation and increased frequency and size of wildfires, before the virus was eradicated in the 1960s.
•Dramatic changes in coastal ecosystems have followed the collapse and recovery of sea otter populations; sea otters maintain coastal kelp forests by controlling populations of kelp-grazing sea urchins.
•The decimation of sharks in an estuarine ecosystem caused an outbreak of cow-nosed rays and the collapse of shellfish populations on which the rays feed.
Despite these and other well-known examples, the extent to which ecosystems are shaped by such interactions has not been widely appreciated.
"There's been a tendency to see it as idiosyncratic and specific to particular species and ecosystems," Estes said.
For example, Schoener points out that some ecologists have viewed trophic cascades as an issue largely for ocean systems, but the review discusses many examples from land.
Schoener’s own work has looked at the impact of a small predator, although large in its own world — lizards on small islands. He has found, for example, that removing the lizards from an island ecosystem can lead to increased damage to plants, because insects that eat the plants (and would normally be eaten by the lizards) multiply.
The review’s findings have profound implications for conservation. "To the extent that conservation aims toward restoring functional ecosystems, the re-establishment of large animals and their ecological effects is fundamental," Estes said. "This has huge implications for the scale at which conservation can be done. You can't restore large apex consumers on an acre of land. These animals roam over large areas, so it's going to require large-scale approaches."
The paper's co-authors include 24 scientists from institutions in six countries. Support for the study was provided by the Institute for Ocean Conservation Science, Defenders of Wildlife, White Oak Plantation, U.S. National Science Foundation, NSERC Canada and NordForsk.
About UC Davis
For more than 100 years, UC Davis has engaged in teaching, research and public service that matter to California and transform the world. Located close to the state capital, UC Davis has more than 32,000 students, more than 2,500 faculty and more than 21,000 staff, an annual research budget that exceeds $678 million, a comprehensive health system and 13 specialized research centers. The university offers interdisciplinary graduate study and more than 100 undergraduate majors in four colleges — Agricultural and Environmental Sciences, Biological Sciences, Engineering, and Letters and Science. It also houses six professional schools — Education, Law, Management, Medicine, Veterinary Medicine and the Betty Irene Moore School of Nursing.
Media contact(s):
•Tom Schoener, Evolution and Ecology, (530) 752-8319, twschoener@ucdavis.edu
•Andy Fell, UC Davis News Service, (530) 752-4533, ahfell@ucdavis.edu
Copyright © The Regents of the University of California, Davis campus
http://www.news.ucdavis.edu/search/news_detail.lasso?id=9942
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