Resilience “Surrogate”

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Estimating Resilience,
Thresholds and Regime Change
Jan Sendzimir
International Institute of
Applied Systems Analysis
Laxenburg, Austria
[email protected]
Outline
 Review Resilience
 Regime Shifts
 Surrogates of Resilience
– Methods to find surrogates
– Examples of application
 Summary
2
Ecological Succession
South-eastern North America
Premise: system tends toward stable equilibrium
Vegetation characteristic of different successional stages
(After E.P. Odum 1971 Fundamentals of Ecology)
3
Hysteresis
Percent
Of Lake
Covered
By MacroPhytes
28
1
27
2
3
26
5, 6…25 4
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.
4
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
5
Resilience:
Three Levels of Meaning
 Metaphor related to sustainability
 A property of dynamic models
 A quantity measurable in field studies
6
Adaptive Cycle
Graphic Metaphor for Dynamism of Resilience
7
Panarchy
a hierarchy of adaptive systems
related by cross-scale interactions.
8
Resilience as Metaphor
Guiding how we define its aspects
To assess resilience in terms of a hierarchal context,
measure the resilience of what to what.
Forest
Stand
Tree
Crown
Panarchy -A Cross-scale Nested
Set of Adaptive Cycles
These aspects change
depending on the
temporal, social, and
spatial scale at which
one measures.
Resilience at one scale can
be subsidized by resilience
at a broader scale in space
and/or time.
9
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.
10
Outline
 Review Resilience
 Regime Shifts
 Surrogates of Resilience
– Methods to find surrogates
– Examples of application
 Summary
11
Regime Shift Examples
12
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).
13
Regime Shift Database
Five 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
14
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
15
Clear Water Regime
Controlling 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)
16
Turbid Water Regime
Controlling 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
17
Outline
 Review Resilience
 Regime Shifts
 Surrogates of Resilience
– Methods to find surrogates
– Examples of application
 Summary
18
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.
19
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
20
Estimating Resilience
Surrogates
Interactive balancing between observation and modeling
21
Assessing R Surrogates
A 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.
22
Assessing R Surrogates
A 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.
23
Outline
 Review Resilience
 Regime Shifts
 Surrogates of Resilience
– Methods to find surrogates
– Examples of application
 Summary
24
Assessing Resilience:
a potential qualitative approach
Australian rangeland ranching
Balancing the interaction between
your economic initiative:debt/income ratio
your ecological constraints: shrub/grass ratio
25
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).
26
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.
27
Increasing variance as threshold approached
28
Variance of P:
Dynamic Simulation
29
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
30
variability may be so narrow as to be useless for empirical purposes.
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
31
Summary
Collaborating 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.
32
Resilience Indicator
Fish Population Dynamics Model
Rates
of
Birth
and
Mortality
(per year)
birth
birth
Fish Population Density (number per ha.)
33
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