ECOLOGICAL STABILITY

'Ecological Stability' can take on any connotation in a continuum ranging from resilience (returning quickly to a previous state) to constancy (lack of change) to persistence (simply not going extinct). The precise definition depends on the ecosystem in question, the variable or variables of interest, and the overall context. In the context of conservation ecology, stable populations are often defined as ones that do not go extinct. Researchers using mathematical models of system dynamics will usually mean Lyapunov stability.

Contents

Types of Ecological Stability

Constancy and Persistence

Resistance, and Inertia

Resilience, Elasticity and Amplitude

Types of Ecological Stability

Due to the inconsistent usage of the term 'stability' in ecological literature, many have proposed using more specific terms.

Constancy and Persistence

Observational studies of ecosystems use 'constancy' to describe systems that remain unchanged. A similar concept is 'persistence' in which specific quantities are ignored, only whether or not the variable—usually population size—is non-zero.

Resistance, and Inertia

These terms deal with a system's response to some perturbation. A perturbation is any externally imposed change in conditions, usually happening in a short time period. 'Resistance' is a measure of how little the variable of interest changes in response to external pressures. 'Inertia' implies, as it does in physics, that the system is changing at some rate that is relatively constant in the face of external fluctuations.

Resilience, Elasticity and Amplitude

'Resilience' is the tendency of a system to return to a previous state after a perturbation. 'Elasticity' and 'Amplitude' are measures of resilience. Elasticity is the speed with which a system returns. Amplitude is a measure of how far a system can be moved from the previous state and still return. Here, ecology borrows the idea of neighbourhood stability and a domain of attraction from dynamical systems theory.