Ecological stability in a stochastic world
Karen Abbott, Case Western Reserve University
Sudden, persistent changes in ecosystem state or configuration, known in ecology as regime shifts, are difficult to predict and a cause of great concern. A large, stable prey population may suddenly collapse to an alternative low-density state in response to a stochastic perturbation, for example, or stochasticity may trigger outbreaks in pest populations that were previously stably suppressed. To explain phenomena like these, ecologists have drawn heavily on deterministic theory that emphasizes the nonlinearities that give rise to multiple stable states and marginalizes the complex role of stochasticity in driving transitions between states. My lab group has recently developed a mathematical formalism -- the quasi-potential -- that allows us to quantify the explicit contributions of both deterministic and stochastic drivers of sudden regime shifts. More broadly, the quasi-potential provides a way to quantify ecosystem stability in a global sense, rather than the highly localized measures of stability typically used in ecology. Given the pervasive influence of large perturbations in nature, this global view promises to yield improved insights into the factors that stabilize or destabilize ecological systems.