Estimating Resilience, Thresholds and Regime Change

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Estimating Resilience, Thresholds and Regime
Change

• Jan Sendzimir
• International Institute of
• Applied Systems Analysis
• Laxenburg, Austria
• sendzim_at_iiasa.ac.at

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Outline

• Review Resilience
• Regime Shifts
• Surrogates of Resilience
• Methods to find surrogates
• Examples of application
• Summary

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Ecological SuccessionSouth-eastern North America
Premise system tends toward stable equilibrium
Vegetation characteristic of different
successional stages
(After E.P. Odum 1971 Fundamentals of Ecology)
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Hysteresis
Percent Of Lake Covered By Macro- Phytes
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5, 625
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.
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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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ResilienceThree 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
To assess resilience in terms of a hierarchal
context, measure the resilience of what to what.
These aspects change depending on the temporal,
social, and spatial scale at which one measures.
Forest
Stand
Tree
Crown
Resilience at one scale can be subsidized by
resilience at a broader scale in space and/or
time.
Panarchy -A Cross-scale Nested Set of Adaptive
Cycles
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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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Outline

• Review Resilience
• Regime Shifts
• Surrogates of Resilience
• Methods to find surrogates
• Examples of application
• Summary

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Regime Shift Examples
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Regime shifts at different speeds
Shrubs
Sediment Phosphorus
Grass
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).
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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 socialecological systems, with a
  threshold change in only one system
• Class 4 Linked socialecological systems with
  reciprocal influences, but a shift in only one
  system
• Class 5 Linked socialecological systems with
  reciprocal influences, shifts in both the
  ecological and social systems

Walker, B. and J. A. Meyers. 2004. Thresholds in
ecological and socialecological systems a
developing database. Ecology and Society 9(2)
3. online URL http//www.ecologyandsociety.org/
vol9/iss2/art3
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Regime Shifts9 Categories
Walker, B. and J. A. Meyers. 2004. Thresholds in
ecological and socialecological 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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Outline

• Review Resilience
• Regime Shifts
• Surrogates of Resilience
• Methods to find surrogates
• Examples of application
• Summary

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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 8pp. 945957.
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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 8pp. 945957.
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Outline

• Review Resilience
• Regime Shifts
• Surrogates of Resilience
• Methods to find surrogates
• Examples of application
• Summary

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Assessing Resiliencea potential qualitative
approach
Australian rangeland ranching Balancing the
interaction between your economic
initiativedebt/income ratio your 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 lakes Whole 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 311318.
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Increasing 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 of conditions 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 of Birth and Mortality (per year)
birth
birth
Fish Population Density (number per ha.)
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