POPULATIONS (Stability of mixed)
| Collection | International Encyclopedia of Systems and Cybernetics |
|---|---|
| Year | 2004 |
| Vol. (num.) | 2(2) |
| ID | ◀ 2588 ▶ |
| Object type | General information |
Heterogeneous populations of a same species, or numerous different species within an ecological system are more stable than homogeneous ones.
R. MARGALEF states: “The greater the number of avenues by which energy may flow through a complex system, the stabler it is” and “… a community exhibiting great stability… is comparable to a system easily convertible within a series of equivalent systems” (1958, p.61).
MARGALEF insists on the importance of “high indices of diversity” — an idea akin to ASHBY's variety — and gives a number of examples in ecosystems.
However, the concept seems quite more general, as it could be applied to any kind of networks, as for example neural or social ones.
The number of avenues through which energy may flow is also reminiscent of BENARD's and PRIGOGINE's dissipative structures, as well as LOTKA's model of the world engine.
At least two different effects can affect the stability of a population:
- Over exploitation- as in the case of hunting or fishing for example, can lead to an excessive reduction of some specific population. In such cases, other species can invade the niche left more or less vacant and the species cannot anymore recuperate, or even maintain itself. This may be caused by decreasing genetic variety or by an excessive rarefaction of individuals.
- Some strong perturbation in the environment - as for example a destructive hurricane-may have a similar effect by damaging the habitat of the species, either for some more or less extended period , or definitively.
The subject is now considered in ecology through patch -dynamics.