Divergence, Sensitivity, and Nonequilibrium in Ecosystems

Abstract

Contemporary theoretical debate in ecology and biogeography is often focused on equilibrium vs. nonequilibrium behavior in ecosystems and on the nature and source of ecosystem dynamics. It is suggested that these debates be recast in terms of the way ecosystems develop and respond to disturbances, rather than in terms of concepts often imported from mathematics, physics, and other fields. Using nonlinear dynamical systems theory, it is shown that key theoretical implications can be cast in terms of geoecologically significant phenomenologies such as divergent evolution, sensitivity to initial conditions and small disturbances, historical contingency, and path dependence. Examples show these phenomena are widely observed in ecosystems. Ecological and biogeographical theory can be problematized from within geography and ecology rather than fuzzy, abstract concepts such as equilibrium, self-organization, “balance of nature,” or chaos. Complexity, sensitivity, variability, nonsteady states, and other concepts often associated with nonequilibrium or complexity-theory frameworks have manifestations that are evident in observable ecological phenomena, in addition to theory and models.