Vasilis Dakos

Aquatic Ecology and Water Quality Management Group Wageningen University, The Netherlands vasileios.dakos@wur.nl, (www.aew.wur.nl/UK/)

Expecting the unexpected:Leading indicators of regime shifts

Nordwijk March 2010

[transitions]

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Clear lakes get turbid

Scheffer and Carpenter, 2003

algae dominated state

macrophyte dominated state

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Cod in North Atlantic crashes

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

deMenocal et al, 2000

The Sahel turned into desert

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Earth climate systems shift

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Financial markets collapse

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Ave

rage

jour

ney

time

We get stuck in traffic jams

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Humans get epileptic seizures

Can we foresee if a system approaches a transition?

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Can we foresee if a system approaches a transition?

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Even if we do not understand the system?

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Same shift different causes:

Small changes big surprisesBig changes big surprises

Critical transition

It depends…

Scheffer 2009

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Critical Transitions workshop 2007

Early Warning Signals

for critical transitions

as Indicators of Resilience

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts Scheffer and Carpenter, 2003

Why should we expect early-warning signals?

Bifurcation point

Eigenvalue goes to zero

Critical slowing down prior to a transition

Van Nes & Scheffer, 2007

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

What does the “eigenvalue goes-to-zero” mean?

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Consequences of critical slowing down

Indicators of transitions in time

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Indicators of transitions in time

Rising variance

Carpenter & Brock, 2006

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Indicators of transitions in time

Guttal & Jayaprakash, 2008

Increasing skewness

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Held & Kleinen, 2004

Indicators of transitions in time

Increasing autocorrelation at-lag-1

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Indicators of transitions in space

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Indicators of transitions in space

pattern formation

Rietkerk et al, 2004

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Indicators of transitions in space

Kéfi et al, 2007

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Increasing grazing

Truncated power law

Spatial Variance

Spatial Skewness

Indicators of transitions in space

Guttal & Jayaprakash, 2008

Spatial Mean

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

overexploited

underexploited

Dakos et al, early online

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Indicators of transitions in space

Increasing spatial correlation

Turbid state

Clear state

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

The indicators seem to work well on models…

23 juni 2005

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Do the indicators work in reality?

But…

23 juni 2005

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Slowing down precedes ancient climate shifts

Shutdown of thermohaline circulation

Model prediction Data

end of Younger Dryas

Dakos et al, 2008

23 juni 2005

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Slowing down precedes ancient climate shifts

Dakos et al, 2008

…more examples

23 juni 2005

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Increasing variance precedes epileptic attacks

McSharry et al, 2003; Scheffer et al, 2009

23 juni 2005

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Increased spatial variance prior to community reorganization

Litzow et al, 2008

� Indirectestimates 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)

�Limitationsin their estimation in real systems (data length, data resolution, scale issues)

�Practical applicability:may work better in spatial than temporal context

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Few concluding points

�How can we identify false positives? (need for proceedures to increase statistical power)

�What kind of monitoring schemesthat can capture the indicators do we need to design?

�Can we develop empirical tests for the indicators next to monitoring for probing the resilience of the system?

�Are they only relativemeasures? Or could an one-timesampling estimate indicate how much fragile the system is?

�How much early is early enough?

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Challenges

23 juni 2005

vasileios.dakos@wur.nl

Thank you for your attention!

Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts

Scientists Seek Warning Signs for Catastrophic Tipping Points

Nordwijk March 2010