Generalists among predators are better for the stability of foodchains in ecosystems
Written by Dr. H. P. Bustami
Tuesday, 11 August 2009
The tiger. The protection of big allrounders like tiger, wolf or lion may play a key role in ecosystem stabiltiy (photo: U.S. Fish and Wildlife Service)
Computer models can contribute to the understanding of complex systems
in nature. Ecosystems belong to complex systems which are influenced by
numerous correlated factors. Food chains for example are part of
ecosystems and difficult to investigate in all with the methods of
field ecology. It is known that food webs are stable over long time
periods, the interactions between different species (predators and
prey) are constant. Yet when ecologists try to calculate models of such
correlations they face some obstacles: they have to reduce usually many
factors to get reasonable scientific output from their models. So still
conclusions drawn from results are still constrained. Now scientists
from Austria, Germany and the US revealed fundamental legalities of
stability in ecosystems: the more diversified the prey species are on
which a predator at the top of a food chain feeds the more stable is
the ecosystem in which it lives. Accordingly a food chain is most
stable if the prey species in the center of a food web or a food chain
have various predators. The scientists used a new method developed by
a workgroup of the Max-Planck-Institute of the Physics of Complex
Systems.
The newly developed calculation method allows to integrate the impact of numerous factors which lead to the complexity of ecosystems. Together with their Austrian and US-American colleagues they could reveal several more fundamental functionalities of ecosystems: " Big predator species stabilize the biocoenosis they live in when they hunt for many different prey animals", explains Ulf Dieckmann, one of the engaged scientists.
Considering the important role of predation for a habitat the protection of endagered big predators like the tiger in India, the lion in Africa or the wolf in the temperate zones (i.e. North America, Europe and Nothern Asia) gets a new dimension: it might play a key role in preserving vast areas of the left natural landscapes on our planet.
Other interesting findings are that obviously smaller ecosystems react very different from larger ones. There are different rules working in both systems. These and other interesting new findings that the international teams found out provide for the first time clear biological coherences which cannot be predicted that precisely with "conventional" methods of field biology. The new calculation method can also be applied to the simulation of other complex systems like gene regulation or human metabolism.
Yet classic field biology will remain: only what has been shown and proved outside in nature eventually can be included into a computer model. No computer will be able to stay outside in nature and wait patiently for the next animal to come in sight. So also in the future human researchers will not be replaced by computer chips.
Source: - Thilo Gross, Lars Rudolf, Simon A. Levin, Ulf Dieckmann Generalized Models Reveal Stabilizing Factors in Food Webs Science (2009), 10.1126/science.1173536
