Stability of Eco-System: Mechanisms, Theories and Models!
There are a number of theories, mechanisms and models to explain stability of eco-system.
1. Homeostatic Mechanisms:
There is in built self-regulating mechanism, known as homeostatic mechanism. In a natural ecosystem through which any change in the eco-system is counter balanced by responses of the system to the change and ultimately eco-system or ecological stability is restored when there happens a rapid increase or decrease in the population of a species in the ecosystem and this change is regulated in such a way that the population returns to its normal position through self-regulating mechanisms within the system. These mechanisms are known as homeostatic mechanisms.
The above concept can nicely be explained with an example. Suppose the population of insects in a specific area increases significantly beyond optimal level due to favourable climate. Then food supply of the region falls short of the demand of increased population resulting in a competition among the insects for food. So, many insects die of starvation and thus the insect population is brought back to its original value and stability is restored.
2. Diversity or Stability Theory:
This theory of eco-system states that ecosystem diversity and complexity increase the stability of population in an eco-system. A number of scientists have proposed this theory in a number of ways. Some of the ideas may be given as below:
(a) According to E.S. Elton (1958), increase in the diversity of food webs promotes eco-system stability because increased food web diversity enhances resilience of the system to outside invasions of the exotic organisms and reduces the fluctuation in the population within a given ecosystem.
(b) According to R. Ii. MacArthur (1955), the ecosystem stability increases with increase in number of links in the food webs because a large number of interacting feeding links provides alternative channels for energy flow and thus, is generated a wide variety of adjustments of the population to environmental stresses in eco-system.
(c) According E. P. Odum, the high species diversity of a mature eco-system representing a climax community related to natural eco-system stability because as the community succession operates, the homeostatic increases due to more protection available to the members of the community against external environmental change.
3. Models:
There are two models to explain stability of ecosystem.
Equilibrium model:
According to this model, the ecosystem always tends towards stability. Whenever the community of an eco-system is disturbed due to external environmental stress, it quickly returns to its original state by some adjustment.
Non-equilibrium model:
According to this model, ecosystem stability is rarely attained because disturbances caused by frequent external environmental changes do not allow developing ordered state of species assemblages in an eco-system.