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Expectations of ecosystem regime shifts
Benjamin Planque and Ulf Lindstrøm
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)
ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05
A simple SDF model for the Barents Sea ecosystem
Super complexNon-linearAdaptiveNot fully observable
Poster A:19
Simple and linearStochastic (trophic flows)Constrained (physiology,
life history, mass-balance)
ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05
SDF output: biomass time series
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
ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05
regime shift detection: results
PC1 variance explained: 30%Frequency of regime shift detection: 18y-1
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
ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05
ICES ASC 2012 – Bergen – Planque and Lindstrøm - A:05
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
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