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Wednesday, September 17, 2008

Marten Scheffer: Thresholds for catastrophic shifts in nature and society

Global change implies gradual changes in climate, pollution or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can sometimes be interrupted by sudden drastic switches to a contrasting state. Similar dramatic shifts punctuating longer quiet periods have occurred in the earth’s climate system and are common in the dynamics of human societies. It is becoming clear that such shifts may often correspond to a phenomenon that is known in mathematical terms as a ‘catastrophic bifurcation’. This has far reaching implications. For instance, they can appear without obvious early warning signals, and the resulting change can be difficult to reverse.

Understanding how such transitions come about in complex systems such as human societies, ecosystems and the climate system is a major challenge. However, in a time where pressures on such systems steadily increase, insight the mechanisms for catastrophic shifts may help predicting such transitions, or even managing systems for enhanced resilience against unwanted shifts.


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