Resilience, panarchy and ecosystem dynamics

Lance Gunderson
Department of Environmental Studies
Emory University


Ecological Thresholds Meetin
g
November 4-5, 2002

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Abstract

Almost thirty years ago, C. S. Holling introduced the word resilience into the ecological literature as a way of helping to understand the non-linear dynamics observed in ecosystems. Ecological resilience was defined as the amount of disturbance that an ecosystem could withstand without changing self-organized processes and structure (defined as alternative stable states). Other authors consider resilience as a return time to a stable state following a perturbation. Two definitions recognize the presence (or not) of multiple stable states (or stability domains), and hence resilience is the property that mediates transition among these states. Transitions among alternative states have been described for many ecosystems, including semi-arid rangelands vegetation, wetlands, lakes, coral reefs, and forests. These transitions appear to have a some similarities, involving interactions among variables operating at different spatial/temporal scales. The transitions also occur as human activities erode resilience through mining of natural capital, changing critical pathways/connections, or through stabilization of key variables (for management purposes). Ecological resilience provides an ecological buffer that protects the system from the failure of management actions that are taken based upon incomplete understanding, and allows managers to affordably learn and change.