space and equilibrium: shifting viewpoints. [28

Abstract: The classical view of ecological systems has been one that assumes a state of equilibrium and stability; this is encapsulated in the ‘balance of nature ’ paradigm. Over the last 30 years ecologists and biogeographers have rejected the view that ecological systems are inherently stable or at some sort of equilibrium. Instead a nonequilibrium view, emphasizing the role of chance events such as disturbance in ecological dynamics, has become dominant. Alongside this change, the way in which the roles of space and spatial heterogeneity in ecological dynamics are viewed has shifted. Classical ecological theory tended to ignore spatial dynamics and heterogeneity and focused instead on temporal pattern. Over the last 20 years this view has also changed and the importance of spatial pattern has been emphasized. Through the explicit consideration of space and spatial pattern it has been shown that spatial heterogeneity may act to either stabilize or destabilize ecological systems and processes. This paper reviews these two changes in the way ecological systems are conceptualized and explores how they are inter-related. Advances in our understanding of the role of space and the nature of equilibrium in ecological systems are discussed within the context of both modelling and empirical studies, as are the problems involved with experimentally testing the large body of spatial theory developed. Key words: disturbance; equilibrium; landscape ecology; scale; spatial models; spatial pattern; succession