Sison, M. (2008). On Clements' The Climax Concept

The Climax Concept by Frederic Clements (Clements 2004) speaks about the climax of successions. Successions are the gradual and orderly process of ecosystem development brought about by changes in community composition. A climax community is a stable group of plants and animals at the end of this successional process. Clements says that there is only one climax for a climatic region. That is, the vegetation profile is due to the climate; it is a response to it, and an indicator of it.

The climax is a stable and self-perpetuating end stage. That is to say that the plants and animals in a climax interact among themselves and with their environment in such a way that the populations of the characteristic organisms are maintained, much as the quantities of gases or liquids are maintained at steady state under conditions of equilibrium.

The factors that give rise to the specific mix of organisms, aside from the organisms themselves, are the climatic conditions of moisture and temperature, and the soil. Thus, under conditions of high moisture, high temperature, and thin soil a region may be dominated by trees characteristic of a rainforest, whereas the same climate but with nutrient-rich soil might be dominated by plants characteristic of swamps.

Climax communities remain stable in the absence of interference. Thus, a disaster such as a volcanic eruption may turn a rainforest into a desolate wasteland; in time, however, a rainforest will be established in the same area.

Over very long periods of time and even in the absence of disasters, however, climaxes are not stable. Ice ages that occur in cycles of hundreds of thousands of years, for example, cause major extinction events that transform the biotic landscape; they are also involved in the emergence of new species. It is thought, for example, that the ancestors of humans emerged from rainforests in Africa that experienced a drastic reduction in precipitation following a long-term geological change and which resulted in the transformation of rainforests into grasslands. Nonetheless, given that moisture, temperature, and soil do not change appreciably, the climax community will remain what it is.

Thus, climaxes are stable; a change in the climax, observed in the short term by changes in the floral and faunal profile, generally signals a change in climate. This is particularly significant today where we are concerned about assessing the effects of human-induced climatic changes.

(Mariel Sison is a student of the University of Asia and the Pacific. m.sison@yahoo.com)

References
Clements, F. (2004). The climax concept. In Keeping Things Whole: Readings in Environmental Science (C. Tickell, J. Coulson, D. Whitfield, A. Preston, Eds.), The Great Books Foundation, USA., pp. 81-85.