Introduction to Ecological Resilience Jan Sendzimir International Institute of Applied Systems Analysis Laxenburg, Austria [email protected].

Introduction to Introduction to Ecological ResilienceEcological Resilience

Introduction to Introduction to Ecological ResilienceEcological Resilience

Jan SendzimirInternational Institute ofApplied Systems Analysis

Laxenburg, [email protected]

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Surprise in Florida Bay

Florida Bay

A B

Sea grassSea grassClear WaterClear Water

Muddy WaterMuddy WaterAlgae BloomsAlgae Blooms

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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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Adaptive CycleGraphic Metaphor for Dynamism of Resilience

Dynamic systems do not tend toward a stable equilibrium, but cycle through four phases (r K )

These definitions emerged from the need to characterize regimes common to resource management systems.

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Resilience Theory

Develop common tools to study the development, decline, and collapse or persistence of socio-ecological 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 structure of a resilient system.

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Ecological Resilienceis related to the…

• Size of the Stability Domain• Amount of change a system can

undergo and still retain the same controls on function and structure

• Degree to which system can: • Self-organize

• Learn and adapt

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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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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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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

Figure from Scheffer et al. 2001 Nature Vol. 413 pp. 591-596.

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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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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. Figure from Scheffer et al. 2001 Nature Vol. 413 pp. 591-596.

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Examples ofMultiple Stable States

Examples ofMultiple Stable States

Coral Reefs– coral vs. algae

Arid Landscapes– shrubland vs. grassland

Shallow Lakes– eutrophic vs. clear

North Florida Forest– longleaf pine savanna &

fire vs. hardwood forest without fire

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Stability Landscape View of

Multiple “Stable” States

An ecosystem may have multiple stability domains. Within each domain many configurations are

possible with the same set of processes organizing structure and function

PotentialEnergy

Ecosystem State

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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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External conditions affect the resilience of multi-stable ecosystems to perturbation.

The bottom plane shows the equilibrium curve. 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.

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Resilience as Metaphor

Simple story to communicate complex ideas– Explain consequences of equilibrium-

based sciences and derivative policies Not as a testable hypothesis

– Theory itself is rarely tested directly As a generator of concepts useful

in generating testable hypotheses

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Resilience as MetaphorGuiding how we define its aspects

Panarchy -A Cross-scale Nested Set of Adaptive Cycles

Water P

Lake Sediment P

Soil P

GeomorphologyThese 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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Resilience:Three Levels of Meaning

Metaphor related to sustainability A property of dynamic models A quantity measurable in field

studies

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Slow Variable(Sediment Phosphorus)

Fast Variable(Water Phos-

phorus)

Resilience of clear water state to large runoff events,.

Plot of system equilibria on axes of fast (water P) and slow (sediment P) variables

In theory and in the model, resilience is tracked as the size of the attractor for the clear water condition.Higher R Lower R

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ResilienceAs a property of dynamic

models Resilience within & between

scales1

Surface waters & non-point source pollution2.

Rangeland management3

Fire-driven forest dynamics41 - Peterson G, Allen CIR, Holling CS. 1998. Ecological resilience, biodiversity, and scale. Ecosystems 1:6–18. 2 - Carpenter SR, Caraco NF, Correll DL, Howarth RW, Sharpley, AN, Smith VH. 1998. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecol Appl 8:559–68. 3 - Janssen MA, Walker BH, Langridge J, Abel N. 2000. An adaptive agent model for analysing co-evolution of management and policies in a complex rangeland system. Ecol Model 131:249–68. 4 - Peterson GD. 1999. Contagious disturbance and ecological resilience [dissertation]. Gainesville (FI): University of Florida.

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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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ResilienceAs a property of dynamic

models Are system-specific. Not all are measurable in the field May be possible to calculate them

in the model.

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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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In practice, resilience could be tracked by monitoring the slowly changing variables that control the attractor for the clear water condition.

Soil P affects the persistence of clear water in 2 ways: 1. Resilience (shape of attractor)2. Probability distribution of disturbances (major runoff events)

Status of 9 Indicator Variables during the Adaptive Cycle

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Using Model Insights to identify R Indicators

Ecological– Soil P, Animal stocking densities, Built area

Institutional– Best practices

• Education, enforcement or innovation

Economic – Markets for water quality, soil runoff

Social– Networks to facilitate appropriate action– Power asymmetries between interest groups

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Resilience:Three Levels of Meaning

Metaphor related to sustainability A property of dynamic models A quantity measurable in field

studies