In This Article Expand or collapse the "in this article" section Multiple Stable States and Regime Shifts

  • Introduction
  • Leading Indicators
  • Lakes

Environmental Science Multiple Stable States and Regime Shifts
James Heffernan, Xiaoli Dong, Anna Braswell
  • LAST REVIEWED: 03 January 2020
  • LAST MODIFIED: 28 March 2018
  • DOI: 10.1093/obo/9780199363445-0095


Why do ecological systems (populations, communities, and ecosystems) change suddenly in response to seemingly gradual environmental change, or fail to recover from large disturbances? Why do ecological systems in seemingly similar settings exhibit markedly different ecological structure and patterns of change over time? The theory of multiple stable states in ecological systems provides one potential explanation for such observations. In ecological systems with multiple stable states (or equilibria), two or more configurations of an ecosystem are self-maintaining under a given set of conditions because of feedbacks among biota or between biota and the physical and chemical environment. The resulting multiple different states may occur as different types or compositions of vegetation or animal communities; as different densities, biomass, and spatial arrangement; and as distinct abiotic environments created by the distinct ecological communities. Alternative states are maintained by the combined effects of positive (or amplifying) feedbacks and negative (or stabilizing feedbacks). While stabilizing feedbacks reinforce each state, positive feedbacks are what allow two or more states to be stable. Thresholds between states arise from the interaction of these positive and negative feedbacks, and define the basins of attraction of the alternative states. These feedbacks and thresholds may operate over whole ecosystems or give rise to self-organized spatial structure. The combined effect of these feedbacks is also what gives rise to ecological resilience, which is the capacity of ecological systems to absorb environmental perturbations while maintaining their basic structure and function. Understanding these complex behaviors is important for managing ecological systems and their responses to environmental change.

General Overviews

In this article, we trace the history of the concept of multiple (or alternative) stable states, highlight important controversies and touch points in its development, and select focal ecosystem studies that represent the range of ecological systems and approaches to the investigation of alternative stable states. The first half of this list focuses on studies with the broadest application across diverse ecological systems. We present conceptual underpinnings in the study of multiple-state ecological systems, beginning with the introduction of the concept and ending with recent efforts to understand why some ecological systems may be more likely to possess multiple stable states. We then proceed to studies that have developed novel and widely applicable approaches to the evaluation of multiple stable state hypotheses and examine how different subdisciplines of ecology have approached inference of multiple stable states. The subsequent sections describe how theoretical and conceptual discussion of the nature of resilience in ecological and socio-ecological systems has deeply informed the development of modern approaches to adaptive management. In the second half of this article, we focus on the development of system-specific understanding of multiple stable states. Within each section, we focus on the first introductions of stable state hypotheses in each system and then trace major system-specific theoretical and empirical advances. We have made an effort to include series of papers that present competing hypotheses, observations, and interpretations, as such controversies are common in the study of multiple stable states. In assembling this article, we have included a range of approaches and scales, and tried to fairly represent disagreements over the interpretation of theory, observation, and experiment. Our article begins with the earliest explicit descriptions of multiple stable states and extends to several emerging frontiers in the study of complex ecological systems. Space limitations have prevented the inclusion of many worthy ecological studies. We encourage readers to use this article as a starting point for the wider exploration of the study of complex systems in ecology and affiliated fields such as physics, geomorphology, economics, and sociology. We also encourage readers to pursue foundational and recent studies in the areas of disturbance ecology and stability theory; a complete overview of these areas is beyond the scope of this collection. These literatures will help readers appreciate the connections of multiple stable state studies to other important topics in ecological theory and research.

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