Act Talk - Vasilis Dakos: Expecting the unexpected

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Large scale catastrophic shifts have been documented for ecosystems, climate systems, oceanic circulation patterns and socio-economic systems. Such shifts may be related to loss of resilience, in the sense that the basin of attraction of the present state of a system is shrinking and the probability that a small disturbance can tip the system into the basin of attraction of a contrasting state increases. Recent theoretical findings suggest that the shrinking of the basin of attraction has fundamental effects on the dynamical behavior of the system. Such effects appear to change with a consistent way as the system approaches the point where the catastrophic transition takes place. Apparently, being able to decipher these effects into measurable quantities of some sort of leading indicators can enhance our ability to assess the risk of upcoming catastrophic shifts, or to manage systems for enhanced resilience to such transitions.

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Act Talk - Vasilis Dakos: Expecting the unexpected

  1. 1. Vasilis DakosAquatic Ecology and Water Quality Management GroupWageningen University, The Netherlandsvasileios.dakos@wur.nl, (www.aew.wur.nl/UK/)Expecting the unexpected:Leading indicators of regime shiftsNordwijk March 2010
  2. 2. [transitions]Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  3. 3. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsClear lakes get turbidScheffer and Carpenter, 2003algae dominated statemacrophyte dominated state
  4. 4. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsCod in North Atlantic crashes
  5. 5. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsdeMenocal et al, 2000The Sahel turned into desert
  6. 6. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsEarth climate systems shift
  7. 7. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsFinancial markets collapse
  8. 8. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsAveragejourneytimeWe get stuck in traffic jams
  9. 9. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsHumans get epileptic seizures
  10. 10. Can we foresee if a system approaches a transition?Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  11. 11. Can we foresee if a system approaches a transition?Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsEven if we do not understand the system?
  12. 12. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsSame shift different causes:Small changes big surprisesBig changes big surprisesCritical transitionIt depends…Scheffer 2009
  13. 13. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsCritical Transitions workshop 2007
  14. 14. Early Warning Signalsfor critical transitionsas Indicators of ResilienceVasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  15. 15. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  16. 16. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsScheffer and Carpenter, 2003Why should we expect early-warning signals?Bifurcation pointEigenvalue goes to zero
  17. 17. Critical slowing down prior to a transitionVan Nes & Scheffer, 2007Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsWhat does the “eigenvalue goes-to-zero” mean?
  18. 18. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsConsequences of critical slowing down
  19. 19. Indicators of transitions in timeVasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  20. 20. Indicators of transitions in timeRising varianceCarpenter & Brock, 2006Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  21. 21. Indicators of transitions in timeGuttal & Jayaprakash, 2008Increasing skewnessVasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  22. 22. Held & Kleinen, 2004Indicators of transitions in timeIncreasing autocorrelation at-lag-1Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  23. 23. Indicators of transitions in spaceVasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  24. 24. Indicators of transitions in spacepattern formationRietkerk et al, 2004Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
  25. 25. Indicators of transitions in spaceKéfi et al, 2007Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsIncreasing grazingTruncated power law
  26. 26. SpatialVarianceSpatialSkewnessIndicators of transitions in spaceGuttal & Jayaprakash, 2008SpatialMeanVasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsoverexploitedunderexploited
  27. 27. Dakos et al, early onlineVasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsIndicators of transitions in spaceIncreasing spatial correlationTurbid stateClear state
  28. 28. Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsThe indicators seem to work well on models…
  29. 29. 23 juni 2005Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsDo the indicators work in reality?But…
  30. 30. 23 juni 2005Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsSlowing down precedes ancient climate shiftsShutdown of thermohaline circulationModel prediction Dataend of Younger DryasDakos et al, 2008
  31. 31. 23 juni 2005Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsSlowing down precedes ancient climate shiftsDakos et al, 2008…more examples
  32. 32. 23 juni 2005Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsIncreasing variance precedes epileptic attacksMcSharry et al, 2003; Scheffer et al, 2009
  33. 33. 23 juni 2005Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsIncreased spatial variance prior to community reorganizationLitzow et al, 2008
  34. 34. Indirect estimates of resilience(indication of proximity to transition not predictive tools)Tools for verifying past regime shifts(indication in establishing a sudden change as a critical transition)Limitations in their estimation in real systems(data length, data resolution, scale issues)Practical applicability: may work better in spatial than temporalcontextVasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsFew concluding points
  35. 35. How can we identify false positives? (need for proceedures toincrease statistical power)What kind of monitoring schemes that can capture the indicatorsdo we need to design?Can we develop empirical tests for the indicators next tomonitoring for probing the resilience of the system?Are they only relative measures? Or could an one-time samplingestimate indicate how much fragile the system is?How much early is early enough?Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsChallenges
  36. 36. 23 juni 2005vasileios.dakos@wur.nlThank you for your attention!Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shiftsScientists Seek Warning Signs for Catastrophic Tipping PointsNordwijk March 2010

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