Navigation Links
Loss of large predators caused widespread disruption of ecosystems
Date:7/15/2011

The decline of large predators and other "apex consumers" at the top of the food chain has disrupted ecosystems across the planet.

The finding is reported by an international team of scientists in a paper in this week's issue of the journal Science.

The study looked at research results from a wide range of terrestrial, freshwater and marine ecosystems and concluded "the loss of apex consumers is arguably humankind's most pervasive influence on the natural world."

According to lead author James Estes, a marine ecologist and evolutionary biologist at the University of California, Santa Cruz, large animals were once ubiquitous across the globe. They shaped the structure and dynamics of ecosystems.

Their decline, largely caused by humans through hunting and habitat fragmentation, has far-reaching and often surprising consequences, including changes in vegetation, wildfire frequency, infectious diseases, invasive species, water quality and nutrient cycles.

Plummeting numbers of apex consumers are most pronounced among the big predators, such as wolves on land, sharks in the oceans, and large fish in freshwater ecosystems. There also are dramatic declines in populations of many large herbivores, such as elephants and bison.

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.

The research, funded in part by the National Science Foundation (NSF), "highlights the unanticipated effects of trophic cascades on Earth systems, including far-reaching processes such as biogeochemical cycles," said David Garrison, director of NSF's Biological Oceanography Program.

"The removal of predators like sharks and sea otters, bass and wolves has consequences," said Garrison, "not only for these species, but for all of us."

"The top-down effects of apex consumers in an ecosystem are fundamentally important, but it is a complicated phenomenon," Estes said. "They have diverse and powerful effects on the ways ecosystems work, and the loss of these large animals has widespread implications."

Estes and co-authors cite a wide range of examples in their review, including:

  • The extirpation of wolves in Yellowstone National Park led to over-browsing of aspen and willows by elk; restoration of wolves allowed the vegetation to recover.
  • Dramatic changes in coastal ecosystems 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.

Despite these and other well-known examples, the extent to which such interactions shape ecosystems was not widely appreciated, scientists say.

"There's been a tendency to see it as idiosyncratic and specific to particular species and ecosystems," Estes said.

One reason for this is the top-down effects of apex predators are difficult to observe and study.

"These interactions are invisible unless there is some perturbation that reveals them," Estes said. "With these large animals, it's impossible to do the kinds of experiments that would be needed to show their effects, so the evidence has been acquired as a result of natural changes and long-term records."

Estes has studied coastal ecosystems in the North Pacific for several decades, conducting research on the ecological roles of sea otters and killer whales. In 2008, he and co-author John Terborgh of Duke University organized a conference on trophic cascades, which brought together scientists studying a wide range of ecosystems.

The recognition that similar top-down effects occur in many different systems was a catalyst for the current paper.

The study's findings have profound implications for conservation.

"To the extent that conservation aims to restore functional ecosystems, the reestablishment 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."


'/>"/>

Contact: Cheryl Dybas
cdybas@nsf.gov
703-292-7734
National Science Foundation
Source:Eurekalert  

Related biology news :

1. Lack of large-scale experiments slows progress of environmental restoration
2. Complete Genomics launches, becomes worlds first large-scale human genome sequencing company
3. Yale journal finds nanomaterials may have large environmental footprint
4. Research uncovers new steps on pathway to enlarged heart
5. Paradigm Tactical Products to be Largest Distributor of Metal/Radiation Detection Wands in United States
6. Less than one month to opening of world’s largest global congress on osteoporosis
7. Small satellite takes on large thunderstorms
8. Pollution at home lurks unrecognized, instead attributed to large-scale environmental disasters
9. Researchers solve piece of large-scale gene silencing mystery
10. Tips for making a green holiday from the worlds largest scientific society
11. Large DNA stretches, not single genes, shut off as cells mature
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Loss of large predators caused widespread disruption of ecosystems
(Date:5/20/2016)... MINNEAPOLIS , May 20, 2016  VoiceIt ... technology partnership with VoicePass. By working ... user experience.  Because VoiceIt and VoicePass take slightly ... two engines increases both security and usability. ... expressed excitement about this new partnership. ...
(Date:5/3/2016)... , May 3, 2016  Neurotechnology, a provider ... MegaMatcher Automated Biometric Identification System (ABIS) , ... multi-biometric projects. MegaMatcher ABIS can process multiple complex ... any combination of fingerprint, face or iris biometrics. ... SDK and MegaMatcher Accelerator , which ...
(Date:4/26/2016)... , April 27, 2016 ... "Global Multi-modal Biometrics Market 2016-2020"  report to their ... , The analysts forecast the global ... of 15.49% during the period 2016-2020.  ... of sectors such as the healthcare, BFSI, transportation, ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... ... June 23, 2016 , ... ... announce the launch of their brand, UP4™ Probiotics, into Target stores nationwide. The ... is proud to add Target to its list of well-respected retailers. This list ...
(Date:6/23/2016)... SPRING, Md. , June 23, 2016 A ... collected from the crime scene to track the criminal down. ... and the U.S. Food and Drug Administration (FDA) uses DNA ... Sound far-fetched? It,s not. The ... genome sequencing to support investigations of foodborne illnesses. Put as ...
(Date:6/23/2016)... Prostate Cancer Foundation (PCF) is pleased to announce 24 new Young Investigator ... Members of the Class of 2016 were selected from a pool of 128 ... About the Class of 2016 PCF Young Investigators ... ... ...
(Date:6/23/2016)... ... June 23, 2016 , ... Supplyframe, the ... the Supplyframe Design Lab . Located in Pasadena, Calif., the Design Lab’s ... how hardware projects are designed, built and brought to market. , The Design ...
Breaking Biology Technology: