YIELD (Maximum sustainable) 1)4)5)
The concept of maximum sustainable yield is generally equilibrium-centered, i.e. based on the postulate that the population or system considered merely fluctuates between permanently stable limits, which will not be crossed.
However, as stated by C.S. HOLLING: "An equilibrium-centered view is essentially static and provides little insight into the transient behavior of systems that are not near the equilibrium. Natural, undisturbed systems are likely to be continually in a transient state; they will be equally so under the influence of man. As man's number and economic demands increase, his use of resources shifts equilibrium states and moves populations away from equilibria" (1976, p.73).
No vegetal, animal or human population exists isolated from its environment, partially made of other species. Thus, some disturbance affecting an apparently unrelated system, may well in due time propagate itself to the population under research. And it could do so in unforeseen ways, triggering wide divergences from the former equilibrium. It may for example lead the population under review to cross an instability threshold and, as a result, introduce bifurcations and a chaotic behavior. This explains why, for instance, overfishing of one species, followed by a population crash, may lead to a permanently depleted population: the global equilibrium has been permanently altered in a way detrimental to the species under focus.
Such situations start now to appear in widely different systems under the pressure of massive abuse by man.
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To cite this page, please use the following information:
Bertalanffy Center for the Study of Systems Science (2020). Title of the entry. In Charles François (Ed.), International Encyclopedia of Systems and Cybernetics (2). Retrieved from www.systemspedia.org/[full/url]
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