Estimating Resilience, Thresholds and Regime Change Jan Sendzimir International Institute of Applied...

Estimating Resilience, Estimating Resilience, Thresholds and Regime Thresholds and Regime

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Estimating Resilience, Estimating Resilience, Thresholds and Regime Thresholds and Regime

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Jan SendzimirInternational Institute ofApplied Systems Analysis

Laxenburg, Austriasendzim@iiasa.ac.at

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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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