The 'abundance biomass comparison' (ABC) method is a means of detecting the effects of anthropogenic perturbations on assemblages of organisms that is underpinned by the r- and i-selection theory (see r-Strategist/i-Strategists). Under stable conditions of infrequent disturbance the competitive dominants in the climax community are i-selected or conservative species with a large body size and long life span, and are usually of low abundance so that they are not dominant numerically but are dominant in terms ofbiomass. Frequently disturbed assemblages are kept at an early suc-cessional stage and comprise r-selected or opportunistic species characterized by small body size, short life span and high abundance. The ABC method exploits the fact that when an assemblage is perturbed the conservative species are less favored in comparison with the opportunists, and the distribution of biomass among species behaves differently from the distribution of numbers of individuals among species.

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