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Estimating Resilience, Estimating Resilience, Thresholds and Regime Thresholds and Regime
ChangeChange
Estimating Resilience, Estimating Resilience, Thresholds and Regime Thresholds and Regime
ChangeChange
Jan SendzimirInternational Institute ofApplied Systems Analysis
Laxenburg, [email protected]
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Review Resilience Regime Shifts Surrogates of Resilience
– Methods to find surrogates– Examples of application
Summary
OutlineOutline
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Ecological SuccessionSouth-eastern North America
(After E.P. Odum 1971 Fundamentals of Ecology)
Premise: system tends toward stable equilibrium
Vegetation characteristic of different successional stages
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Response of charophyte vegetation in the shallow Lake Veluwe to increase and subsequent decrease of the phosphorus concentration. Red dots represent years of the forward switch in the late 1960s and early 1970s. Black dots show the effect of gradual reduction of the nutrient loading leading eventually to the backward switch in the 1990s.
PercentOf LakeCoveredBy Macro-Phytes
Hysteresis1 2
3
4
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5, 6…25
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Defining Resilience
• Size of the Stability Domain• Amount of change a system can
undergo and still retain the same controls1 on function and structure
• Degree to which system can: • Self-organize
• Learn and adapt
1 – set of reinforcing relations and feedbacks
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Resilience:Three Levels of Meaning
Metaphor related to sustainability A property of dynamic models A quantity measurable in field
studies
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Adaptive CycleGraphic Metaphor for Dynamism of
Resilience
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Panarchy
a hierarchy of adaptive systems related by cross-scale interactions.
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Resilience as MetaphorGuiding how we define its aspects
Panarchy -A Cross-scale Nested Set of Adaptive Cycles
Crown
Tree
Stand
ForestThese aspects change depending on the temporal, social, and spatial scale at which one measures.
To assess resilience in terms of a hierarchal context,
measure the resilience of what to what.
Resilience at one scale can be subsidized by resilience at a broader scale in space and/or time.
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Stability Landscape View of Evolution
Shift from one domain to the next as the relations and feedbacks change
As it changes, a system
modifies its own possible states.
Here a smaller and smaller
perturbation can shift the
equilibrium from one stability
domain to another.
Finally the stability domain
disappears and the system
spontaneously changes state.
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Review Resilience Regime Shifts Surrogates of Resilience
– Methods to find surrogates– Examples of application
Summary
OutlineOutline
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Regime Shift Examples
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Regime shifts at different speeds
Lake water quality
Stylized trajectories through time of the fast (---) and slow ( ) variables in lakes (thick blue lines) and rangelands (thin red lines) under high levels of phosphate inflow (lakes) and grazing (rangelands).
Sediment Phosphorus
Shrubs
Grass
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Regime Shift DatabaseFive Classes
Class 1. No linkage, externally driven change in ecological or social systems
Class 2. No linkage, internally driven change in the ecological or social systems
Class 3: Linked social–ecological systems, with a threshold change in only one system
Class 4: Linked social–ecological systems with reciprocal influences, but a shift in only one system
Class 5: Linked social–ecological systems with reciprocal influences, shifts in both the ecological and social systems
Walker, B. and J. A. Meyers. 2004. Thresholds in ecological and social–ecological systems: a developing database. Ecology and Society 9(2): 3. [online] URL: http://www.ecologyandsociety.org/vol9/iss2/art3
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Regime Shifts–9 Categories
Walker, B. and J. A. Meyers. 2004. Thresholds in ecological and social–ecological systems: a developing database. Ecology and Society 9(2): 3. [online] URL: http://www.ecologyandsociety.org/vol9/iss2/art3
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Clear Water RegimeControlling Processes
Phosphorus inputs from basin– Agric Methods (intensity & history)
• Fertilizer type & application rate• Field size and shape• Buffer strips on field margins• Equipment size & use frequency
Soil Deposition related to soil type Rain events (duration, frequency, intensity)
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Turbid Water RegimeControlling Processes
Phosphorus recycling from lake bottom– Ecological components
• Bethos sediment type• Macrophyte / algae ratio• Ratio bottom feeders / predators• Zooplankton that eat algae
Physical components– Storm events (intensity & frequency)– Lake shape and depth
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Review Resilience Regime Shifts Surrogates of Resilience
– Methods to find surrogates– Examples of application
Summary
OutlineOutline
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Factors that challenge how we assess
resilience Context (indicators vary with it)
– a web of relations that can change with time, spatial pattern, and the specifics of the local ecology and/or society.
Direct observation very difficult– events are rare, evidence may be
dispersed in time and space. Manipulation impossible or unethical.
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Resilience “Surrogate”
Contextual complexity– mandates that multiple models and
multiple estimators be used in conjunction to measure different aspects of resilience.
Indicator – too narrow a term– to reflect this more systematic
approach
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Estimating Resilience Surrogates
Interactive balancing between observation and modeling
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Assessing R SurrogatesA Stepwise methodology
Step 1 – Assess and define “problem”– - What aspect of the system should be resilient and to
what?
Step 2 – ID feedback processes– - What variables are changing?
– - What drivers create change? – - What feedbacks reinforce or damp change?
Bennett, E.M., Cumming, G.S., Peterson, G.D. (2005). "A Systems Model Approach to Determining Resilience Surrogates for Case Studies." Ecosystems 8:pp. 945–957.
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Assessing R SurrogatesA Stepwise methodology
Step 3 – Model the System Structure– What are the key elements and how are they
connected?– - Feedback loops and related key variables.
Step 4 – Use model to identify Resilience surrogates
» - What is the threshold value of the state variable and how far is it from the threshold?
» How fast is the state variable moving toward or away from the threshold?
Bennett, E.M., Cumming, G.S., Peterson, G.D. (2005). "A Systems Model Approach to Determining Resilience Surrogates for Case Studies." Ecosystems 8:pp. 945–957.
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Review Resilience Regime Shifts Surrogates of Resilience
– Methods to find surrogates– Examples of application
Summary
OutlineOutline
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Assessing Resilience:a potential qualitative
approach
Australian rangeland ranchingBalancing the interaction between
your economic initiative:debt/income ratioyour ecological constraints: shrub/grass ratio
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Variance – evidence of approaching regime
shift?System Variance evident as Regime shift
approached
Ocean-circulation Spectra shifted to lower frequencies
Shallow lake Variance increase in Individual macrophytes
Terrestrial landscape mosaic
Spatial variance of patches increased near threshold to percolation
Field Data from lakesWhole lake manipulation by artificial forcing with added phosphorus
exhibited increases in variance in phytoplankton biomass (Cottingham et al. 2000), and measures of variance in phosphorus recycling rates foretold threshold crossings
one to two years in advance (Carpenter 2003).
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Rising Variance of Phosphorus – a signal of approaching regime shift
Carpenter, S.R., Brock, W.A. 2006. Rising variance: a leading indicator of ecological transition. Ecology Letters 9: 311–318.
28Increasing variance as threshold approached
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Variance of P: Dynamic Simulation
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Possible Mechanism
Fast Variable (Phosphorus in water)
– relaxes to equilibrium after small shocks.
Slow variables (Phosphorus in sediments) – SV change slow change in two
attractors making regime shift more likely Variance (SD) in Fast variable increases
In some types of systems, increased variability may occur over a wide zone ofconditions near a transition, while in other types of systems the zone of increased variability may be so narrow as to be useless for empirical purposes.
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Resilience Surrogates already proposed by social scientists
Organizational and institutional flexibility for dealing with uncertainty and change.
Social capital (including trust and social networks)
Social memory (including experience for dealing with change) Folke, C. (2006). "Resilience: The emergence of a perspective for social-ecological systems analyses." Global Environmental Change in press
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SummaryCollaborating in assessing resilience
Methods– A version of Bennett et al. 2004
Resources– Database of regime changes– Review of resilience surrogates
already proposed by social scientists.
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Resilience Indicator Fish Population Dynamics
Model
Rates ofBirth andMortality(per year)
Fish Population Density (number per ha.)
birth
birth
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