Science - September 4, 2009

Scheffer identifies warning signs of major transitions

Different systems - from the brain to finance - send out similar warning signals before the onset of a major transition.

Epilepsy and financial market clashes therefore have more in common than meets the eye. Spinoza prize winner Prof. Marten Scheffer of the Aquatic Ecology and Water Quality Management Group has hit upon universal warning signals in a system. These signals precede a major transition, a so-called tipping point. Scheffer says that very different kinds of system resemble one another as they approach such a tipping point. His findings appear today in the scientific journal Nature. 'Every system has tipping points, whether it's the brains, an ecosystem or a financial system', explains Scheffer, while USA Today waits on another line. 'Systems can be different and yet send out the same warning signals before a transition.' His co-author Dr. Egbert van Nes, who is in the same chair group, says that the application of these signals is both new and promising.
An example of a general warning signal before a transition is a slow recovery after disruption, called a 'critical slowing down'. Another warning signal preceding a critical transition is 'flickering'. Van Nes: 'Flickering is when disruptions cause a system to oscillate between two equally balanced situations, such as from 'cultivated' to 'desert' and vice versa, or from a clear to a murky state in a lake.' A third signal is when fluctuations in a system slow down but become bigger. It's as if today looks more and more like yesterday. The elements in a system will increasingly resemble one another. This principle is evident in the transformation of an area into a desert. Patches of vegetation look more and more alike just before the critical transition into desert landscape.  Something similar happens in an epilepsy attack: the brain cells display notable synchronic activity just before the attack. When a financial system nears a tipping point, its elements - people - also become copycats. 'In an uncertain financial market situation, traders do what other traders do', explains Scheffer. 'When things start sliding, everyone follows and panic breaks out.' 

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