Assessing Biodiversity and Ecological Stability

Abstract

Letter: Jocelyn Kaiser, in her News Focus article "Rift over biodiversity divides ecologists" (25 Aug., p. 1282), repeats the conventional wisdom that Robert May's theoretical work in the 1970s showed that diversity works against stability. The centerpiece of May's work involved Monte Carlo samples of models--the larger the system and the stronger the interactions among populations, the smaller the proportion of the sample that would be stable. Complex ecological systems are generally not, however, the outcome of some sampling process, but arise through development over time with the addition, growth, decline, and elimination of populations. Several modeling studies in the 1970s and 1980s showed that, whereas stable systems may be extremely rare as a fraction of the systems being sampled, they can be readily constructed over time by the addition of populations from a pool of populations or by elimination of populations from systems not at a steady state (1). Both sides of the debate reviewed by Kaiser about whether biodiversity enhances ecosystem function depend, conceptually, on a sampling view of ecological complexity. The developmental view would be preferable for any serious consideration of the implications of human interventions within ecosystems.