1. Expectations of ecosystem regime shifts Benjamin Planque and Ulf Lindstrøm

2. ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05 Ecosystem regime shifts sudden, high-amplitude, infrequent events, which persist over decadal to multidecadal time scales and are evident on multiple trophic levels (Lees et al., 2006) Regime shifts in the North Pacific (Hare and Mantua, 2000)

3. ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05 A simple SDF model for the Barents Sea ecosystem Super complex Non-linear Adaptive Not fully observable Poster A:19 Simple and linear Stochastic (trophic flows) Constrained (physiology, life history, mass-balance)

4. ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05 SDF output: biomass time series

5. ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05 Ecosystem regime shift detection 3000y SDF simulation Conventional regime shift detection algorithem (Principal Component Analysis + Change point analysis) At least 10y between regime shifts Output: Frequency of regime shifts

6. ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05 regime shift detection: results PC1 variance explained: 30% Frequency of regime shift detection: 18y -1

7. ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05 Conclusions Regime/trophic shifts are observed in real systems The Stochastic Dynamic Food-web model shows that these are expected features of ecosystems, given few reasonable assumptions… … and without exceptional events in the climate forcing In the Barents Sea, the null expectation is that substantial changes in ecosystem structure and functions occur every few decades

8. ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05

9. Temporal changes in ecosystems to measure resilience Resilience ~ the ability to maintain structure and function substantial changes in structure or function ~ Lack of resilience Peterson et al., 1998