Measuring the Inertia and Resilience of Ecosystems

The resilience of natural ecosystems is a property of keen interest to both theoretical and applied ecologists. Resilience, in this context, refers to the degree, manner, and pace of restoration of initial structure and function in an ecosystem after disturbance. It is an important ecological characteristic, reflecting ultimately the nature and complexity of homeostatic processes in an ecosystem. Discussions of the concept of ecosystem resilience are relatively recent, and a variety of terms has been proposed for properties of resilience. The ability of a natural ecosystem to restore its structure following acute or chronic disturbance (natural or human-induced) is here termed resilience, consistent with the use of Clapham (1971). This same set of properties is subsumed under the term by May (1973), Holling (1973), and Orians (1975) and termed elasticity by Cairs and Dickson (1977). Given the definition of resilience above, it would seem useful to limit stability to the pattern of fluctuations in a relatively unimpacted ecosystem over time, a usage consistent with the first eight properties of discussed by Whittaker (1975a). Traditionally, fluctuations in ecosystem structure have referred to variations in population densities of component species, but in theory other measures of ecosystem structure or function (e.g., biomass, net primary production, nutrient stocks, species richness) could be used. Since different properties of ecosystem structure and function will not necessarily vary at parallel rates, however, the ecosystem parameters chosen for study will have a