Revised 24 May 2019
All ecosystems have developmental stages corresponding to that of a single organism - birth, early rapid growth, followed by maturity. Each developmental stage brings and ecosystem closer to steady state, a state of homeostasis in which there is a dynamic equilibrium interaction between the ecosystem and its physical environment.
Succession is a natural process where organisms within the same ecosystem succeed one another by maximising their energy inflow until a highly stable climax ecosystem develops. During this succession stage, energy and nutrients are added to the ecosystem with the result that the net ecosystem production is high. The ratio of gross production P to respiration R is greater than 1 and the food chains of the ecosystem are linear.
As an ecosystem approaches climax, the Gross Production to Respiration Ratio (P/R ratio) approaches 1, the net ecosystem production approaches 0, and the food chains of the ecosystem tend to be woven into food webs. A climax ecosystem is stable and in a condition of internal self-regulation where feed-back mechanisms enables the ecosystem to return to equilibrium following any stress of change in climate, energy, and nutrient resources.
There is a relationship between diversity or complexity and the stability of an ecosystem. Increasing the complexity of an ecosystem may or may not increase the stability of the system. The development of a high degree of diversity can favour the collection of energy and provides flexibility in cases where there are changes in the relative availability of energy resources. On the other hand, the energy required for organising diversity is large and can be either an aid or a drain on energy. During the succession stage there is a low diversity of species, but a high level of diversity of special adaptations within the species. At climax there tends to be a high level of species diversity. A careful evaluation of an ecosystem should be made before any change in diversity is considered and implemented.
Humans are omnivores who can eat both plants and meat. We are now no longer hunters and gatherers. Instead, we are now essentially grazers who either feed off grain directly or indirectly through the breeding of animals which we eat. Agriculture is an attempt to increase the P/R ratio for human consumption by preventing the natural process of succession and decreasing diversity. Humankind has been able to crop a high yield from an unstable agricultural ecosystem by feeding in energy in the form of fertilizers and insecticides. Monoculture systems of growing crops, building dams and roads, and pollution threaten the homeostasis of ecosystems. Environmental impact assessments of proposed developments should use an eco-energetic approach to establish whether proposed development will result in runaway instabilities in the surrounding ecosystem.