The "Balance of Nature" and "Population Control"

Abstract

The notion that nature is in some sort of "balance" with respect to population size, or that populations in general show relatively little fluctuation in size, is demonstrably false. The thesis of Hairston, Smith, and Slobodkin that "populations of producers, carnivores, and decomposers are limited by their respective resources in the classical density-dependent fashion" is based on a series of assumptions about these trophic levels which are, in all probability, false. Even if the assumptions are true, this conclusion does not follow from them. A realistic basis for building models dealing with the changes of numbers in populations would include the following propositions: All populations are constantly changing in size. The environments of all organisms are constantly changing. Local populations must be recognized and investigated if changes in population size are to be understood. The influence on population size of various components of environment varies with population density, among species, among local populations, and through time.