Control theory for ecosystem. At this point it would be well to review the elementary concepts of cybernetics, which is the science of controls. Control in any system, whether a simple temperature – regulating home – heating system or a complex ecosystem, depends on feedback, which occurs when output (or part of it) feedback as input. Referring back to figure 1-3, if we were to draw a curving line from the output arrow back to the input arrow, we would have added a ‘’feedback loop’’ to the system diagram. When the feedback input is positive (like compound interest, which is allowed to become part of the principal), the quantity grows. Positive feedback is thus ‘’deviation accelerating’’ and, of course, is necessary for the growth and survival of young organisms and young ecosystems, as pointed out in post 6. However, to achieve and orderly growth that does not ‘’boom and bust’’ there must also be negative feedback, or ‘’deviation – countering’’ input, especially as limits are approached.

natural ecosystems studying

        In studying natural ecosystems we are impressed with the numerous and intricate negative feedback mechanisms that have evolved, as, for example, the controls on foliage – eating insects in forest, as described in post 1. Man’s fuel powered urban and agricultural systems have been, until recently at least, under the influence of strong positive feedback with economic and political policies providing strong forcing functions for a quantitative growth. Many people have assumed that negative feedback will automatically develop, as saturation is approached, and, therefore, it is not necessary for us to plan very far ahead or worry about the future. Such an attitude is completely untenable when growth is rapid; negative feedback must be established will before limits are to prevent dangerous overshoots.