Presentation on theme: "Resilience: Exploring Stability and Change in the Dynamics of Systems Jan Sendzimir International Institute of Applied Systems Analysis Laxenburg, Austria."— Presentation transcript:
Resilience: Exploring Stability and Change in the Dynamics of Systems Jan Sendzimir International Institute of Applied Systems Analysis Laxenburg, Austria
2 Ecological Succession South-eastern North America (After E.P. Odum 1971 Fundamentals of Ecology)
3 The result of a century of fire suppression in North America? More than 180 million hectares extremely vulnerable to fire. Vulnerability
4 Sudden Collapse of the Oldest, Richest Fishery on Earth Northwest Atlantic Cod Harvest (1895 – 1993) Annual Catch Of Cod (1000 tons) 1900 tons 90 tons 25 yearsMore than 400 years 2003 – after 10 years, no sign of recovery
5 Catastrophic Examples of Sudden Shifts and Flips 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
6 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 Outline
7 Lake Eutrophication The flip from clear to turbid water Some lakes remain clear for decades until one summer storm churns up the sediments, and it remains turbid for decades, despite all “cures.”
8 Eutrophication can proceed slowly for decades as a natural enrich- ment that fills lakes. Human waste can accelerate the process to a few years.
9 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. Conventional Models of Relations between Ecosystem States And Conditions Clean Turbid Poor Enriched
10 Response of charophyte vegetation in the shallow Lake Veluwe to increase of the phosphorus concentration in the 1960s. Phosphorus in Water Percent Of Lake Covered By Macro- Phytes
11 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. Percent Of Lake Covered By Macro- Phytes Hysteresis
12 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.
13 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 Outline
14 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.
16 Lynx-Hare Phase Space revealing a simple symmetry within complex fluctuations
17 State Space Views of Ecosystem Dynamics
18 Landscape and State Space Views of “Industrial Optimism”
19 Stability Landscape View of “Ecological Pessimism”
20 Stability Landscape View of Multiple Stable States
21 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.
22 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.
23 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
24 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
25 Ecosystem Resilience Dynamic 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
26 Collapse 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.
27 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 Outline
28 Global Geographical Distribution of Taiga Forest
29 Spruce Budworm in Boreal Forest in New Brunswick, Canada
30 Spruce Budworm Adults and Larvae
31 Simulated Dynamics of Boreal Forest Budworm and Foliage Surface Area
32 Forest Growth Changes the Rules: Feedback becomes more likely
33 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?
34 System Dynamics focus 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)
35 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 Outline
36 Ecological Resilience Measures system integrity as the capacity to absorb disruption and remain the same kind of ecosystem. Emerges from cross-scale interactions Depends upon: Control of Disturbance Regulation of Renewal
37 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
38 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
39 What Promotes Resilience? Regulation of Renewal (or Regenerative potential ) –Stored Resources –Soil depth, organic content, seed bank –Water (aquifer, lake, river) –Nutrients in biomass
40 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
41 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)
42 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 Outline
43 Australian Rangelands
44 Geographical Distribution of Australian Rangelands
45 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.
46 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.
47 Management for Resilience in Australian 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 Ratio of Debt Income More grass More shrubs
48 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.
49 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.
50 Sources of Uncertainty Complexity 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
52 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.
53 Shallow Lake Model Different sets of Processes dominate To maintain each Stability domain. Turbid Algal state processes Clear water Macrophyte state processes
54 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 toxicology From Endocrine Disruptor Chemicals 1. EDC’s have many counter-intuitive properties: threshold assumption and non-monotonic effects dosage effect Toxic Non-Toxic Conventional Assumption Observed Dose-Effect Relations Synergy At a certain dosage, Chemical A is safe by itself but toxic in combination with Chemical B
56 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.
57 Panarchy A Cross-scale Nested Set of Adaptive Cycles
58 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
59 Cross-Scale Interatcions: Revolt and Remember
60 Surprise in Florida Bay Florida Bay Sea grass Clear Water Muddy Water Algae Blooms