Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Big vegetarian mammals can play a critical role in maintaining healthy ecosystems

18.01.2007
Removing large herbivorous mammals from the African savanna can cause a dramatic shift in the relative abundance of species throughout the food chain, according to scientists from Stanford University, Princeton University and the University of California-Davis. Their findings were published in the Jan. 2 edition of Proceedings of the National Academy of Sciences (PNAS).

In the study, the research team used large electric fences to exclude cattle, elephants, zebras and other herbivorous mammals from experimental plots on a ranch in central Kenya from May 2004 to December 2005. During that time, the scientists monitored changes in the populations of trees, beetles, lizards and other plant and animal species.

"All of the species studied increased in abundance in the absence of large plant-eating mammals," said lead author Robert Pringle, a graduate student in the Department of Biological Sciences at Stanford. These results are examples of what ecologists call cascading effects, he added.

Although elephants and zebras do not interact directly with insects, they share plants as a food source, Pringle noted. Previous studies have shown that when elephants and zebras are experimentally removed or hunted out, plant matter accumulates and insect populations increase.

"With an increase in insects comes an increase in the insects' predators, such as lizards," Pringle said. "Thus, the actions of a few dominant species ripple throughout the ecosystem."

The authors also found that the strength of the cascading effects varied considerably across the landscape, and that it was possible to predict where the effects would be weak or strong in terms of "primary productivity"-the transformation of solar energy into plant tissue during photosynthesis. Plants in areas of high primary productivity grow faster, making more energy available throughout the food chain. The study revealed that cascading effects are weaker in places where productivity is high, probably "because more productive plant communities absorb the impacts of herbivory and buffer the remainder of the community," the authors wrote.

"For years, ecologists debated whether cascading effects occurred in terrestrial environments, and even then, most studies centered around the activities of top carnivores, such as wolves," Pringle said. "While top predators are undeniably important to ecological function, this new study shows that large herbivores can also play critical roles."

Extinctions, past and present

The PNAS study is timely for several reasons, he added: "Large herbivorous mammals are declining throughout Africa and worldwide, and have already gone extinct in many places. Our results suggest that these declines are likely to have complicated, and often unanticipated, consequences for the entire ecosystem."

North America is one place where mammoths, giant sloths, camels and other large herbivores once were common. But most of these mega-fauna species were eliminated during the Pleistocene epoch that ended about 10,000 years ago, raising questions about how these extinctions affected ecological processes. According to the authors, the cascading effects demonstrated in the experiment may have been important "in the history and evolution of ecosystems that today are bereft of large herbivores, and that although many of these cascades went extinct at the end of the Pleistocene along with the large herbivores that caused them, their legacies may well remain."

In 2005, another team of scientists made headlines by advocating a program of "Pleistocene re-wilding"-introducing large mammals from Africa and elsewhere into North America to simulate the lost Pleistocene fauna. Pringle made clear that his team's results do not speak to the wisdom of re-wilding. Nevertheless, he said, the new study should serve as a reminder that "the ecology we observe today is a product of history," and that humans have long played a leading role in that history.

"Humanity faces a lot of important decisions about how to manage Earth's ecosystems in the next few decades," he said. "By studying the ecology of places like Africa, where large mammals still exist, we can get glimpses of how life used to be organized in places like Europe and North America, and those inferences help explain phenomena that would otherwise seem strange. Snapshots of ecological history, even if from another continent, can help guide us to more robust conclusions about today's ecosystems and their conservation management."

Mark Shwartz | EurekAlert!
Further information:
http://www.stanford.edu

More articles from Ecology, The Environment and Conservation:

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht International network connects experimental research in European waters
21.03.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

Fingerprint' technique spots frog populations at risk from pollution

27.03.2017 | Life Sciences

Big data approach to predict protein structure

27.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>