Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study Suggests Predators Are Vital to Health of Ecosystems

04.12.2001


The question of which forces control terrestrial ecosystems lies at the heart of a long-standing debate among ecologists. One theory, the so-called bottom-up theory, suggests that plant defense mechanisms exert control by limiting food availability for herbivores. Top-down theorists, however, suggest that predators limit the numbers of herbivores and hence their impact on the vegetation. Now new findings in the current issue of the journal Science that describe animal communities isolated for 15 years weigh in on the side of predators as crucial to controlling an ecosystem.



An international team of 11 authors studied a dozen predator-free islands isolated since 1986 by rising water in a hydroelectric impoundment in Venezuela. Two of the large islands, together with two mainland sites, served as control systems. The smaller islands, the authors write, are "highly aberrant, consisting of a suite of consumers without predators." As such, they provide a unique opportunity to test top-down control.

The researchers found highly inflated numbers of consumer animals on some of the islands as compared with the mainland—including 35 times more rodents, 25 times more howler monkeys, 10 times more iguanas and 100 times more leafcutter ants. "This is very strong evidence for top-down regulation," says lead author John Terborgh of Duke University. "If predators are gone, then the number of these consumers explodes." Hinting at the complexity of ecosystem control, however, the reproductive rates of the howler monkey on one island did exhibit bottom-up control, in that the birth rate was one quarter of that found on a less-populated island.


The lack of predators has been troublesome for the plants on the islands. "The vegetation is in a state of collapse," Terborgh notes. "Plant species that can survive under this massive onslaught by herbivores are the ones that are incredibly tough and terribly toxic." Such observations serve as warnings, the authors conclude, "because large predators which impose top-down regulation have been extirpated from most of the continental U.S. and, indeed, much of the earth’s terrestrial realm."

Sarah Graham | Scientific American
Further information:
http://www.sciam.com/news/120301/3.html

More articles from Ecology, The Environment and Conservation:

nachricht Despite government claims, orangutan populations have not increased. Call for better monitoring
06.11.2018 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Increasing frequency of ocean storms could alter kelp forest ecosystems
30.10.2018 | University of Virginia

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>