Observing, understanding, and utilizing resilience mechanisms of ecological systems

Transcription

1 Observing, understanding, and utilizing resilience mechanisms of ecological systems Volker Grimm, Department of Ecological Modelling Page 1

2 DICTIONARY DEFINITIONS of RESILIENCE The ability to recover quickly from depression or discouragement The ability to recover quickly from illness, change, or misfortune Strength of character An act of springing back The property of a material that enables it to resume its original shape or position after being bent, stretched, or compressed Page 2

3 RESILIENCE IS APPEALING BECAUSE We can relate it to ourselves/organisms Organisms/systems must have stability/buffer mechanisms, otherwise they would not exist These mechanisms have a certain capacity A single stressor, or multiple stressors, can exceed this capacity Then, functioning of the organisms/system might get lost All this means to view ecosystems as selfdefined entities, BUT THEY ARE NOT! Page 3

4 WHAT ARE WE TALKING ABOUT? What is resilience? Wrong question! What, exactly, do we mean by resilience, and how and for what do we want to use this concept? We are talking about: Complex systems including adaptive agents, self-organized, self-similar over time Resilience is one of myriads of stability concepts in ecology but it has become the dominant one Page 4

5 STABILITY CONCEPTS IN ECOLOGY A terminological morass: Page 5

6 STABILITY CONCEPTS IN ECOLOGY Page 6

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8 STABILITY CONCEPTS IN ECOLOGY Essentially, there are three different stability properties Resistance: Staying essentially unchanged despite the presence of disturbances Recovery: Returning to the reference state (or dynamics) after a temporary disturbance Persistence: Persistence through time of an ecological system Page 8

9 Three stability properties Resistance: Changes in state variables are buffered, i.e. they change not as much as assumed based on the fluctuations of drivers. Recovery: State variables return back to their initial range of values after temporary changes based on disturbances. Persistence: The analysed system is defined by a set of characteristic spatial-temporal patterns of state variables on explicitly defined scales. It exists as identifiable unit over long time periods.

10 HOLLING s RESILIENCE "Resilience determines the persistence of relationships within a system and is a measure of the ability of these systems to absorb changes of state variables, driving variables, and parameters, and still persist. In this definition resilience is the property of the system and persistence or probability of extinction is the result. Holling combines resistance, recovery, and persistence into one concept: resilience However: This mixes two different kinds of stability concepts Page 10

11 ANALYTIC VS. SYNTHETIC STABILITY CONCEPTS Distinguish between synthetic and analytic stability concept Synthetic: Persistence Holistic: applies to the entire system Analytic: Recovery, resistance Reductionistic: applies to specific ecological situations, defined by state variables, scales, disturbance (Grimm and Wissel 1997) Page 11

12 ANALYTIC SYNTHETIC linear threshold H: full resistance I: limited resistance, full recovery J: limited resistance, no recovery K: no resistance, no recovery multi-stable Oliver et al Scheffer et al. 2001

13 DILEMMA Synthetic: persistence Holling s resilience Exploring and speaking about resilience will lead us to comprehensive understanding of ecologies Analytic: resistance, recovery We can only achieve myriads of more or less unrelated stability assessments of very limited explanatory power (state variables, scales, disturbances) Page 13

14 SOLUTIONS IN AN IDEAL WORLD Synthetic: Clearly define the system! But: Nobody wants to hear this, because it is very difficult, and depends on our questions or purpose Analytic: Explore recovery and resistance for a wide range of ecological situations (variables, scales, disturbances)! But: Infeasable for real ecoystems Page 14

15 Weise et al., in preparation Page 15

16 RESILIENCING Verbing : Shift from property (resilience) to action (resiliencing) forces us to focus on resilience mechanisms. This leads to asking better questions. Focus on services acknowledges the normative aspect of dealing with resilience Resiliencing: restoring, maintaining, or developing both ecological and socioecological resilience mechanisms at all relevant levels of organization and spatial and temporal scales. Building/promoting resilience: Biggs et al. 2012, Chapin et al. 2009, Desjardins et al. 2015, Oliver et al. 2015, Spears et al. 2015

17 THREE TIME HORIZONS AND DECISION CONTEXTS Figure: Hanna Weise.

18 Three time horizons and decision contexts Reactive Actions clear Knowledge sound Stakeholder acceptance high Uncertainty low or irrelevant Adjustive Actions scientifically clear Unspecific knowledge Stakeholder awareness high, acceptance often low Uncertainty high, but known Provident Actions unclear No knowledge about new systems No stakeholder awareness Uncertainty unknown

19 Time horizon: Short Intermediate Long Decision context Perceived urgency Stakeholder acceptance Uncertainty

20 Time horizon: Short Intermediate Long Recovery Focus Resistance Ecosystem service(s) Ecosystem processes Biodiversity as service Biodiversity as mechanism

21 AGENDA REGARDING RESILIENCING Compile examples of lock-ins of resilience mechanisms due to actions in certain contexts and time frames Compile resilience mechanisms and relate them to the three types of resiliencing INSTALL the memes /ideas: THERE IS NO ONE-SIZE-FITS ALL RESILIENCE WHATSOEVER! WE NEED TO FOCUS ON MECHANISMS of resistance and recovery and how they generate persistence Page 21

22 TAKE HOME MESSAGES Holling s resilience combines the three concepts: resistance, recovery, and persistence Analytic concepts (resistance, recovery) are reductionistic (variables, scales, disturbance) Synthetic concept (persistence) is holistic (entire system) A possible way out of this dilemma: resiliencing Three different time horizons and decision contexts for resiliencing: reactive, adjustive, provident There is no one-size-fits-all resilience, or resiliencing Page 22

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