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System collapse and resilience
In October 2017 many were alarmed when researchers reported an apparent collapse in insect populations in Germany. The researchers found that the biomass of flying insects in protected areas had fallen a remarkable 77% over the past nearly three decades. They warned of an ‘ecological Armageddon’. “If we lose the insects then everything is going to collapse,” they said.
‘Collapse’ is an evocative word. It conjures dark images failure, disorder, and loss, and it implies that something has fallen into disorder. The word collapse is frequently used in discussions about sustainability, usually in terms of risks of collapse and the need to avoid collapse. However, developing an understanding of factors that actually cause or predict collapse has been limited by inconsistent and unclear definitions of collapse.
A review of social-ecological collapses by Graeme Cumming from Australia’s James Cook University and centre researcher Garry Peterson uses ideas from resilience theory to clarify thinking about collapse. Published in Trends in Ecology & Evolution, their paper reviews the study of collapse across economics, archeology, and ecology and then suggests a new framework for studying collapse in social-ecological systems.
Understanding collapse requires the comparing different cases of collapse, however when collapse is defined inconsistently and unclearly, such comparisons are impossible, and block the development and testing of different theories of collapse.
Collapse is the shadow of resilience, consequently studying collapse is indirectly the study of what makes a system resilient
Garry Peterson, co-author
In their proposed definition of ‘collapse’, Cumming and Peterson argue it is necessary to explicitly define what is collapsing. "Not doing this basic thing leads to confused conflicts about collapse among researchers who are focusing on different aspects of a place or system," Cumming explains.
Defining collapse, requires specifying the identity of the system being studied, as this can be used determine its elements, characteristics and thresholds of change. Once the system has been identified, the authors argue that its collapse can be determined using four criteria:
The first criterion is that the identity of the system must be lost. This can occur if important components of the system disappear.
The second criterion is that this loss should happen fast. The term ‘fast’ is relative to the system being considered, so it depends on the intrinsic rates of the system’s identifying components and varies accordingly. A gradual ‘degrading’ of the system would not qualify as system collapse under the second criterion.
The third criterion is that the collapse involves substantial loss of social-ecological capital. The key word here is ‘substantial’, which will vary between systems. Using case studies, Cumming and Peterson have found that quantitative thresholds are useful for focussing attention on the trends in the system. For example, a 99% decline in the Newfoundland Cod spawner biomass represented a substantial loss of social-ecological capital and was a solid indicator of the system’s collapse.
The fourth criterion is that the consequence of the collapse must be lasting. This criterion implies that short-term perturbations in system dynamics, while interesting, do not represent system collapse. Cumming and Peterson argue that if all four criteria for collapse are met, the system will undergo dramatic change in structure, function or both. Using a systematic approach to defining system collapse is the first step in developing our understanding of it.
So how does the study of collapse help us? An agreed framework for comparing collapse allows us to develop and test general theories about mechanisms of collapse. In their paper, Cumming and Peterson propose a framework that links the systematic definition of system identity and collapse with an understanding of system structure and dynamics to allow us to develop and test theories relating to the mechanisms of collapse.
In their review of system collapse case studies, the authors identified 14 potential mechanisms that may cause collapse in social-ecological systems. They were also able to link specific collapse mechanisms with different types of system structure. While there are disagreements about the exact causes of collapse in some of the case studies, the review does demonstrate the value of combining system identity with a clear definition of collapse in future work.
As Peterson explains, “Collapse is the shadow of resilience, consequently studying collapse is indirectly the study of what makes a system resilient.”
Trade-offs between the resilience of one part of a system and the fragility of another may be unavoidable, but knowing how and where a system is fragile gives people advanced warning as well as the capacity to work to reduce the risk of failure in that part of the system. As the world changes and new disruptions of current social-ecological systems occur, a science of collapse is needed to create a resilient and sustainable future.
Cumming and Peterson use a review of 17 case studies of social-ecological system collapse to propose a systematic approach to defining system collapse. Further to this, the authors propose a framework for collapse research that allows for comparison between case studies and the development of a general theory of collapse and its mechanisms in social-ecological systems. Drawing on previous work regarding system structure by the first author, the framework is shown to be able to link specific collapse mechanisms with the pre-collapse structure of the system. The authors proceed to discuss the benefits of a systematic approach to collapse research to the theory and practice of system management.
Garry Peterson is professor in environmental sciences with emphasis on resilience and social-ecological systems at the Stockholm Resilience Centre. His research combines three themes: abrupt systemic change, how ecological changes impacts people, and using futures thinking to improve navigating surprising social-ecological change. He is head of subject for the centre’s Sustainability Science PhD programme.
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