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 Safeguarding sustainability through forest certification mapping
27.06.2017 | International Institute for Applied Systems Analysis (IIASA)

nachricht Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

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: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>