Resilience: Exploring Stability and Change in the Dynamics of Systems Jan Sendzimir International Institute of Applied Systems Analysis Laxenburg, Austria

Resilience:Resilience: Exploring Stability and Change in Exploring Stability and Change in

the Dynamics of Systems the Dynamics of Systems

Resilience:Resilience: Exploring Stability and Change in Exploring Stability and Change in

the Dynamics of Systems the Dynamics of Systems

Jan Sendzimir

International Institute of

Applied Systems Analysis

Laxenburg, Austria

[email protected]

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Ecological SuccessionSouth-eastern North America

(After E.P. Odum 1971 Fundamentals of Ecology)

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The result of acentury of fire suppression in North America?

More than 180 million hectaresextremely vulnerableto fire.

Vulnerability

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Sudden Collapse of the Oldest, Richest Fishery on

Earth

Northwest Atlantic Cod Harvest (1895 – 1993)

AnnualCatchOf Cod(1000 tons)

1900 tons

90 tons25 yearsMore than 400 years

2003 – after 10 years, no sign of recovery

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Catastrophic Examples ofSudden Shifts and Flips

Catastrophic Examples ofSudden Shifts and Flips

Coral Reefscoral vs. algae

Arid Landscapesshrubland vs. grassland

Shallow Lakeseutrophic vs. clear

North Florida Forest– longleaf pine savanna & fire vs.

hardwood forest without fire

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Shallow Lake dynamics Resilience Theory

– Stability Landscapes• Visual descriptions of systems dynamics

– Boreal Forest Case Study– Factors Influencing Resilience

• Control of disturbance• Regulation of Renewal

Australian Rangeland Case Study– Managing for resilience

Summary

OutlineOutline

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Lake EutrophicationThe flip from clear to turbid water

Some lakes remain clear for decades until onesummer storm churns up the sediments, and itremains turbid for decades, despite all “cures.”

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Eutrophicationcan proceedslowly for decadesas a natural enrich-ment that fills lakes.Human waste canaccelerate the processto a few years.

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Possible ways in which ecosystem equilibrium states can vary with conditions such as nutrient loading, exploitation or temperature rise.

In a and b, only one equilibrium exists for each condition.

ConventionalModels ofRelations betweenEcosystem StatesAnd Conditions

Clean

Turbid

Poor Enriched

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Response of charophyte vegetation in the shallow Lake Veluwe to increase of the phosphorus concentration in the 1960s.

Phosphorus in Water

PercentOf LakeCoveredBy Macro-Phytes

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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

Hysteresis

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If the equilibrium curve is folded backwards (c), three equilibria can exist for a given condition. Equilibria on the dashed middle section are unstable and represent the border between the basins of attraction of the two alternative stable states on the upper and lower branches.

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Summary

OutlineOutline

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Resilience Theory Invert the normal pessimism

– “If the world really is collapsing, why do so many ecosystems persist?”

Develop common tools to study the decline, collapse or persistence of ecological, economic and social systems.

You are resilient if your identity persists:– In the face of shock or disturbance the same set

of organizing processes remain to control the behavior and appearance of a resilient system.

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Lynx-Hare Phase Space

revealing a simple symmetry within complex fluctuations

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State Space Views of Ecosystem Dynamics

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Landscape and State Space Views of “Industrial Optimism”

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Stability Landscape Viewof “Ecological Pessimism”

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Stability Landscape View of Multiple Stable States

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Stability Landscape View of Evolution

Shift from one domain to the next as the rules 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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If the equilibrium curve is folded backwards (c), three equilibria can exist for a given condition. Equilibria on the dashed middle section are unstable and represent the border between the basins of attraction of the two alternative stable states on the upper and lower branches.

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Figure 3 External conditions affect the resilience of multi-stable ecosystems to perturbation. The bottom plane shows the equilibrium curve as in Fig. 2. The stability landscapes depict the equilibria and their basins of attraction at five different conditions. Stable equilibria correspond to valleys; the unstable middle section of the folded equilibrium curve corresponds to a hill. If the size of the attraction basin is small, resilience is small and even a moderate perturbation may bring the system into the alternative basin of attraction.

Shallow lake dynamics from clear to turbid and back

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Resilience

“…the amount of change or disruption that will cause an ecosystem to switch from being maintained by one set of mutually reinforcing processes and structures to an alternative set of processes and structures.”

– G. Peterson 2000

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Ecosystem ResilienceDynamic Exchanges between

Stability and Disturbance

Stability is recognized for its contributions to productivity and bio-geochemical cycles.

Like ‘invigorating’ gymnastics, disturbances contribute to diversity, structure and resilience.

The engine of evolution and resilience.– Not disturbance alone– Nor stability alone– But the cycling between them

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Collapse of ResilienceCollapse of Resilience Surprise from Cross-scale Interactions

– Occasionally Natural systems develop to a stage of “over-maturity” where elements are over-connected.

– They become accidents waiting to happen. – Then collective activities of small scale

processes can “cascade upward” and cause the system to flip to another system type.

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Summary

OutlineOutline

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Global Geographical Distribution of Taiga Forest

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Spruce Budworm in Boreal Forest in New Brunswick, Canada

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SpruceBudwormAdults andLarvae

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Simulated Dynamics of Boreal ForestBudworm and Foliage Surface Area

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Forest Growth Changes the Rules:Feedback becomes more likely

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The Dynamics of Change:Paradoxical Twins

Unpredictable Change - Surprises Smooth, continuous change suddenly

interrupted by reversal or collapse.

Predictable Change - Return Times Fires, Floods, Pest Outbreaks

How do we reconcile these contradictions?

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System Dynamicsfocus attention on destruction and re-organization

as well as growth and conservation

“The adaptive cycle …a useful metaphor not a testable hypothesis.”

(Carpenter et al. 2001)

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Summary

OutlineOutline

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Ecological ResilienceEcological ResilienceMeasures system integrity as the capacity to absorb disruption and remain the same kind of ecosystem.

Emerges from cross-scale interactions

Depends upon:Control of DisturbanceRegulation of Renewal

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What Promotes Resilience?

Control of Disturbance

– Disturbance Frequency and Intensity

– Technical Restrictions

– Chesapeake Shellfish Fishery

– Herbivore grazing/browsing

– Fire or logging in forests

– Development in floodplain– Local rain cycle in river basins

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What Promotes Resilience?Control of Disturbance

– Capacity to Absorb Disturbance– Landscape morphometry

– Room for the River Program - Rhine river

– Habitat availability

– Ability to migrate (connectivity of landscape)

– Spatial Heterogeneity (mangroves, eel grass)

– Processing and Cycling of Resources– Cross-scale functional reinforcement– Within-scale functional diversity

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What Promotes Resilience?Regulation of Renewal (or

Regenerative potential)

–Stored Resources

–Soil depth, organic content, seed bank

–Water (aquifer, lake, river)

–Nutrients in biomass

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What Promotes Resilience?Regulation of Renewal

–Facility of Response–Recolonization distance

–Proximity of Youth (Kobe Earthquake)

–Biodiversity

–Cross-scale functional diversity

–Capacity to adapt, to generate novelty, to innovate

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What Promotes Resilience?Regulation of Renewal (Regenerative potential)

–Availability of Information

–Viability of cultural information transfer - Cultural Capital–Language (Norway surrenders to English)

–Customs (education, discourse)

–Politics and institutions

–Human Memory & Population Age Structure– Cree People and Caribou (Birkes)

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Summary

OutlineOutline

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Australian Rangelands

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Geographical Distribution ofAustralian Rangelands

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For Ecosystems with threshold effects and multiple stable states

Supply of ecosystem services– Can arise from many combinations of state

variables.– Depend more on the stability domain the system is

in than any particular combination of state variables.

Management strategy– Sustain or enlarge the stability domain (system

configuration) rather than emphasize a particular state or variable to maximize production.

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Ecosystem Dynamics and Services in Australian Rangelands

Ecosystem services (livestock products)– Depend on amount of grass which

depends on amount of shrubs– When shrub cover (area) exceeds a

threshold, there is not enough grass to sustain a fire that will control the shrubs.

– The system moves on an undesirable trajectory toward a Shrub stability domain.

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Management for Resilience inAustralian Rangelands

Possible trajectories of a 2-variable system through time. The positions of the dashed lines on the axes represent critical threshold levels. (Walker, B. et al. 2002)

Ratio Woody vegetation / Grass

Ratioof

Debt Income

More grass More shrubs

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Expanding the Domain of Desirable Options

Biophysical axis – increase the proportion of perennial

species in the grass sward, control grazing pressure

Socio-economic axis – increasing access to alternative (external)

sources of income • (game farming, tourism).

Not maximization of one goal: profit or biodiversity.

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Summary

Phase Space and Stability Landscapes visually describe system dynamics.

Resilience theory allows us – to describe how different variables

influence system dynamics at different scales.

– to manage for how a system moves and retains its integrity as opposed to single goals.

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Sources of UncertaintyComplexity

Feedbacks, delays in system interactions– Completely confuse conventional models

• Causation: Life is a series of events• Change: proceeds smoothly and monotonically

Changing structure - shifting relationships

• synergy

1. EDC’s have many counter-intuitive properties:

• threshold assumption and non-monotonic effects

• exposure during early ontogeny (sensitive periods)

• transgenerational effects

2. Integrating behavioral and evolutionary ecology

• limitations of using inbred strains

• limitations of tests in artificial conditions

e.g., increase susceptibility to predation and infection

Old Standards of toxicology in Jeopardy

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Sources of Uncertainty:Complexity

Changing structure - shifting relationships– Ecosystems have more than one

equilibrium, each determined by a different set of key processes

– Shifts in dominance of key processes cause shifts from one equilibrium to another.

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Phosphorusin Soil

Phosphorusin Water

Phosphorusin Sediment

Biomass inAlgae

Biomass in Macrophyte

s

P Input to Soil P diffusion Soilto Lake

PSedimentation

P Resuspension& Recycling

P Neutralization

P flushed out

P Burial

P Burial fraction

Wind StormWater Mixing

-

SedimentationFraction

-

Algal Bloom&Turbidity

P NeutralizationFraction

P Flush Fraction

Lake Depth &Morphometry

Biomass &Nutrients

Max PRecycleRate

P Direct Inputto Lake

Bottomfeeder Fish

PhytoplanktivoresShallow Lake Model Different sets ofProcesses dominateTo maintain eachStability domain.

Turbid Algal state processes

Clear water Macrophyte state processes

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Ways of explaining reality

Events

Patterns, Trends

Systemic Structures

Mental Models

What just happened?

What’s been happening?Have we been here or some place similar before?

What are the forces at play contributing to these patterns?

What about our thinking allows this situation to persist?

New challenges for toxicologyFrom Endocrine Disruptor Chemicals

1. EDC’s have many counter-intuitive properties:• threshold assumption and non-monotonic effects

dosage

effect

Toxic

Non-Toxic

ConventionalAssumption

ObservedDose-Effect Relations

• Synergy At a certain dosage, Chemical A is safe by itself but toxic in combination with Chemical B

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Why Panarchy Theory?

Rationalize the interplay between:– Predictable and unpredictable– Evolutionary change and persistence

Explore the world where different variables are nested inside of one another and change at different scales in space and time.

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PanarchyA Cross-scale Nested Set of Adaptive Cycles

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Why Panarchy Theory?To Account for Dynamics

Within a level– Adaptive cycle describes the engine of

novelty, Creative Destruction, and renewal or reorganization.

Between levels– Revolt – the cascade upward of tiny events– Remember – the context of the next larger

level at climax constrains the next smaller level in times of renewal

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Cross-Scale Interatcions:Revolt and Remember

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Surprise in Florida Bay

Florida Bay

A B

Sea grassSea grassClear WaterClear Water

Muddy WaterMuddy WaterAlgae BloomsAlgae Blooms

Documents

Resilience: Exploring Stability and Change in the Dynamics of Systems Jan Sendzimir International Institute of Applied Systems Analysis Laxenburg, Austria