GUNDERSON, Lance et al - {2000} - Ecological Resilience—In Theory and Application
ECOLOGICAL RESILIENCE—IN THEORY AND APPLICATION
Author Information
Author: Lance H. Gunderson
Affiliation: Dept. of Environmental Studies, Emory University, Atlanta, Georgia 30322
E-mail: lgunder@emory.edu
Key Terms
Resilience
Stability
Stable States
Biodiversity
Adaptive Management
Abstract
In 1973, C. S. Holling introduced the term resilience into ecological literature to assist in understanding non-linear dynamics observed in ecosystems.
Definition of Ecological Resilience: The amount of disturbance an ecosystem can withstand without altering the self-organized processes and structures, termed alternative stable states.
Resilience is also viewed as the return time to a stable state after a perturbation.
Introduction of Adaptive Capacity: Describes processes that modify ecological resilience.
Recognition of multiple stable states (or stability domains) allows resilience to be considered as a property mediating transitions between these states.
Transitions among stable states have been documented across various ecosystems: semi-arid rangelands, lakes, coral reefs, and forests.
Maintaining ecological resilience serves as a buffer against management failures and enables managers to learn and adapt in dynamic environments.
Introduction
The term resilience has appeared in various meanings over three decades since its introduction.
Importance of Resilience Definitions: Different interpretations lead to varying policies and management actions.
The review is structured into three sections:
Conceptual Overview: Reviews resilience definitions and examples from modeling and field experiments.
Resilience in Relation to Ecosystem Properties: Discusses resilience's interaction with other ecosystem characteristics.
Management Implications: Explores how ecological resilience informs management strategies for complex human-nature systems.
Resilience, Stability, and Adaptive Capacity
Two Definitions of Resilience:
Holling outlines two aspects of stability concerning resilience.
Stability as a persistence near equilibrium represents efficiency and predictability.
Resilience indicates dynamic system behavior far from equilibrium (i.e., ability to absorb disturbances without changing state).
Global Equilibrium:
Resilience defined as time for a system to return to equilibrium after disturbance; implies existence of a single global equilibrium state (engineering resilience concept).
Emphasis on designing systems for optimal functionality assumes that system behavior is predictable and manageable.
Multiple Equilibria:
Resilience emphasizes conditions far from equilibrium, allowing systems to experience disturbances and switch between regimes or stability domains.
Definition of Ecological Resilience: The limit of disturbance a system can absorb before transitioning to a different stable state.
Multiple examples of ecosystems with alternative stable states (e.g., grass-dominated vs. woody-dominated ecosystems, clear vs. turbid lakes) illustrate this resilience framework.
Heuristic Models to Explain Resilience
Ball and Cup Heuristic:
The ball represents system states, while the cup depicts stability domains.
Engineering Resilience: Determined by the slope of the cup's sides (shaping return time).
Ecological Resilience: Characterized by multiple cups signifying different stable states and the width of stability domains defines resilience.
Adaptive Capacity
The alteration of key variables influencing stability domains leads to human-induced ecosystem state changes.
Key variables change at slow rates, impacting stability (e.g., nutrient levels in wetlands, species compositions).
Adaptive Capacity Concept: Refers to the ecosystem's ability to remain within a stability domain while the structure and rules defining stability are altered.
Ecosystem Dynamics and Stable States
Literature evaluates transitions among stability domains across ecosystems, addressing whether multiple stable states exist and what facilitates transitions.
Importance of human activities in altering resilience and stability of ecosystems (e.g., transitions in lake systems, wetlands, and savanna rangelands).
Shallow Lakes
Distinctions between clear (rooted macrophytes) and turbid (planktonic algae) water states
Nutrient cycling and sediment stabilization contribute to resilience in clear water states.
Turbid states maintained by physical variables and disturbances (e.g., wind-driven mixing).
Shifts between states occur through trophic relationships and hysteresis effects demonstrate the complexities of transitions.
Wetlands: The Everglades
Nutrient enrichment after agricultural activities led to significant changes in species dominance within the Everglades (transition to cattail dominance).
Resilience closely linked to soil nutrient dynamics and key ecosystem processes that variate over different temporal and spatial scales.
Semi-arid Rangelands
Alternative stable states identified between grassy and woody-covered regions, where transitions mediated by grazing pressures.
Established woody communities reduce fire frequency, further influencing stability and resilience frameworks.
Resilience in Ecosystems: Themes and Process
Resilience as an emergent property relates to self-organization of ecosystems across time affected by disturbances.
The Adaptive Cycle Model describes phases of ecosystem development:.
Exploitative Phase: Characterized by rapid colonization.
Conservation Phase: Energy and material accumulation.
Creative Destruction Phase: Disturbances release accumulated ecological capital.
Reorganization Phase: High vulnerability and potential for novel structures.
The phase of the adaptive cycle influences resilience properties, as systems can fluctuate between high resilience and collapsing states.
Resilience and Biodiversity
Discussion on biodiversity's role in ecosystem stability and resilience expands beyond simplicity of stable states.
Increasing species number influences ecosystem efficiencies; determinants are classified into 'drivers' (keystone species) and 'passengers' (species without significant ecosystem influence).
Removing critical drivers impairs ecological resilience significantly compared to 'passenger' species.
Focusing on functional diversity across scales enhances ecosystem stability and performance.
Managing for Resilience in Policy and Practice
Case histories illustrate the relationship between management, resilience, and resource crises.
Three response strategies in face of crises:
Do Nothing: Assuming the system may revert back without intervention.
Active Management: Attempting to restore to a desired state.
Adaptation: Acknowledging irreversible changes and adjusting strategies accordingly.
The effectiveness of management actions is influenced by the ecological resilience of the system.
Uncertainty, Understanding, and Resilience
20th-century management focused on control of variability to achieve a singular goal (i.e., yield maximization) led to weakened resilience over time.
Adaptive Management: An integrative framework acknowledging continuous change and uncertainties aiming for continual adaptation and learning.
Viewing management policies as hypotheses allows for structured testing and adjustment based on observed ecosystem responses.
Restoration and Maintenance of Resilience
Strategies to enhance resilience include:
Increasing system buffering capacity.
Managing processes across multiple scales.
Nurturing sources of renewal.
Institutions play a vital role in enhancing resilience through mechanisms fostering social learning, engagement, and trust.
Summary and Conclusions
Distinction between resilience in engineering (return time) and ecological resilience (disturbance absorption).
Adaptive Capacity as a crucial consideration for maintaining and restoring resilience in ecological systems based on interaction with multi-scale processes.
Acknowledgments
Supported by a grant from the MacArthur Foundation aiding the Resilience Network. Contributions recognized from various scholars and collaborators within the context of this research.