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