Insects as Regulators of Ecosystem Processes

I. Development of the Concept

II. Ecosystems as Cybernetic Systems

A. Properties of Cybernetic Systems

B. Ecosystem Homeostasis

C. Definition of Stability

D. Regulation of Net Primary Productivity by Biodiversity

E. Regulation of Net Primary Productivity by Insects

III. Summary

INSECTS, AND OTHER ORGANISMS, INEVITABLY AFFECT THEIR ENVIRONMENT through spatial and temporal patterns of resource acquisition and redistribution. Insects respond to environmental changes in ways that dramatically alter ecosystem conditions, as discussed in Chapters 12-14. These effects of organisms do not necessarily provide cybernetic (stabilizing) regulation. However, the hypothesis that insects stabilize ecosystem properties through feedback regulation is one of the most important and revolutionary concepts to emerge from research on insect ecology and should be considered in making pest management decisions in natural ecosystems.

The concept of self-regulation is a key aspect of ecosystem ecology. Vegetation has a documented role in ameliorating variation in climate and biogeo-chemical cycling (Chapter 11), and vegetative succession facilitates recovery of ecosystem functions following disturbances. However, the concept of self-regulating ecosystems has seemed to be inconsistent with evolutionary theory (emphasizing selection of "selfish" attributes) (e.g., Pianka 1974), with variable successional trends following disturbance (e.g., H. Horn 1981) and with the lack of obvious mechanisms for maintaining homeostasis (e.g., Engelberg and Boyarsky 1979).

The debate over the self-regulating capacity of ecosystems, and especially the role of insects, is somewhat reminiscent of debate on the now-recognized importance of density-dependent feedback regulation of population size (Chapter 16) and is a useful example of how science develops. The outcome of this debate has significant consequences for how we manage ecosystems and their biotic resources. Although controversial, this concept is an important aspect of insect ecology, and its major issues are the subject of this chapter.

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