Rivet-Popper Hypothesis

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The rivet-popper hypothesis , also known as the rivet hypothesis , rivet hypothesis or niche complement hypothesis, is a hypothesis on the relationship between biodiversity , in particular species diversity , of ecosystems and their function . The hypothesis was, in the form of a metaphorical fable, by the American researchers Paul R. Ehrlich and Anne H. Ehrlich in their book Extinction: The Causes and Consequences of the Disappearance of Species(German: The silent death) invented. It is not a scientific hypothesis in the strict sense that could become the subject of a research program, but rather an illustrative linguistic image with heuristic use. Predictions or tests of the connection between biodiversity and function are extremely difficult and practically impossible in the field, so that the connections are more theoretically derived.

formulation

The fable told by the Ehrlichs in the introduction to their book reports (here based on the German version) of a mechanic from a fictional airline who is seen unscrewing screws from the wing of an airplane. When confronted, he justifies himself that airplanes have a large margin of safety, so that a few screws more or less do not matter, and he can sell them for a good price. After the (rhetorical) question of whether you would like to fly with such an airline, they compare the screws in the airplane with the types of the “spaceship earth” as an ecosystem. When humans cause some of these to become extinct , not much bad seems to happen at first. Gradually, however, the functionality would be lost until it finally breaks down.

In the original English version, there was no talk of screws, but of rivets (English: rivet ) that are pulled (English: popping ), which is where the name comes from.

classification

The relationship between the number of species and the functioning of an ecosystem is still controversial in ecology . A distinction is usually made between four possible hypotheses, of which the rivet hypothesis is one. Alternative hypotheses would be:

  • Null hypothesis : There is no connection whatsoever between species number and function.
  • Redundancy Hypothesis: A minimum number of species are required for the function. Once this has been achieved, additional species are redundant and their absence has no significant effects. For this hypothesis, in order to also use an airplane metaphor in direct comparison, the essential key types were compared with the pilots, the remaining (redundant) types with the passengers of an airplane. The hypothesis goes back to the ecologist Brian Walker, who conducts research in Australia.
  • Idiosyncrasy hypothesis. What happens when species are lost depends on the individual case. General predictions are impossible.

The connection has been intensively researched to this day. Most scientists are currently of the opinion that the null hypothesis (no correlation) cannot apply to the data. But the rivet hypothesis is also criticized because it suggests a linear relationship. In fact, it seems more likely that species each form groups with a similar function, which are called "functional groups" or guilds in ecology . Species within a guild are considered to be interchangeable to a certain extent. According to this, many species would actually be redundant, but above a certain threshold the system collapse would become more and more likely. Paul Ehrlich and Brian Walker themselves said in an article that there is basically no big difference between their concepts. The individual redundant types would be a kind of insurance against the failure of the system; although they are not absolutely necessary for the functioning of the system, they increase security.

literature

  • Paul Ehrlich & Anne Ehrlich: Extinction: The Causes and Consequences of the Disappearance of Species. Random House, New York, 1981.
  • German: The silent death: The extinction of plants and animals. from the American by Engelbert Schramm. S. Fischer, Frankfurt a. M. 1983

Individual evidence

  1. ^ Shahid Naeem: Biodiversity, Ecosystem Functioning and Ecosystem Services. Chapter VI.2 in Simon A. Levin (editor): The Princeton Guide to Ecology. Princeton University Press, 2009. ISBN 978-0-691-12839-9
  2. ↑ John H. Lawton: The role of species in ecosystems: Aspects of ecological complexity and biological diversity. Pages 215 to 230 in: Takuya Abe, Simon A. Levin, Masahiko Higashi (editors): Biodiversity: An Ecological Perspective. Springer, 2012. ISBN 978-1-4612-1906-4 . on p. 216
  3. ^ Brian H. Walker (1992): Biodiversity and Ecological Redundancy. Conservation Biology 6 (1): 18-23. online at JSTOR
  4. ↑ Stefan Scheu: Biological diversity and ecosystem functions. In: Matthias E. Hummel, Hans-Reiner Simon, Jürgen Scheffran (editor): Biodiversity conflict field: Preservation of biological diversity - interdisciplinary problems. IANUS work report 7, 1999, Darmstadt.
  5. ^ Paul Ehrlich & Brian Walker (1998): Rivets and Redundancy. BioScience 48 (5): 387.