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2012, Science
All ChangeResearch on early warning signals for critical transitions in complex systems such as ecosystems, climate, and global finance systems recently has been gathering pace. At the same time, studies on complex networks are starting to reveal which architecture may cause systems to be vulnerable to systemic collapse.Schefferet al.(p.344) review how previously isolated lines of work can be connected, conclude that many critical transitions (such as escape from the poverty trap) can have positive outcomes, and highlight how the new approaches to sensing fragility can help to detect both risks and opportunities for desired change.
Nature, 2009
Complex dynamical systems, ranging from ecosystems to financial markets and the climate, can have tipping points at which a sudden shift to a contrasting dynamical regime may occur. Although predicting such critical points before they are reached is extremely difficult, work in different scientific fields is now suggesting the existence of generic early-warning signals that may indicate for a wide class of systems if a critical threshold is approaching.
2011
Critical transitions are sudden, often irreversible, changes that can occur in a large variety of complex systems. Signals that warn of critical transitions are highly desirable, but their construction can be impeded by limited availability of data. We propose a method that can significantly reduce the amount of time series data required for a robust early warning signal by using other information about the system. This information is integrated through the framework of a generalized model. We demonstrate the applicability of the proposed approach through several examples, including a previously published fisheries model.
2014
Social ecological systems are often difficult to investigate and manage because of their inherent complexity1. Small variations in external drivers can lead to abrupt changes associated with instabilities and bifurcations in the underlying dynamics2-4. Anticipating critical transitions and divergence from the present state of the system is particularly crucial to the prevention or mitigation of the effects of unwanted and irreversible changes5-10. Recent research in ecology has focused on leading indicators of regime shift in ecosystems characterized by one state variable5,7,11,12. The case of systems with several mutually interacting components, however, has remained poorly investigated13, while the connection between network stability and research on indicators for loss of resilience has been elusive14. Here we develop a theoretical framework to analyze early warning signs of instability and regime shift in social ecological networks. We provide analytical expressions for a set of...
Many dynamical systems, including lakes, organisms, ocean circulation patterns, or financial markets, are now thought to have tipping points where critical transitions to a contrasting state can happen. Because critical transitions can occur unexpectedly and are difficult to manage, there is a need for methods that can be used to identify when a critical transition is approaching. Recent theory shows that we can identify the proximity of a system to a critical transition using a variety of so-called 'early warning signals', and successful empirical examples suggest a potential for practical applicability. However, while the range of proposed methods for predicting critical transitions is rapidly expanding, opinions on their practical use differ widely, and there is no comparative study that tests the limitations of the different methods to identify approaching critical transitions using time-series data. Here, we summarize a range of currently available early warning methods and apply them to two simulated time series that are typical of systems undergoing a critical transition. In addition to a methodological guide, our work offers a practical toolbox that may be used in a wide range of fields to help detect early warning signals of critical transitions in time series data.
Scientific Reports, 2015
Many real world systems are at risk of undergoing critical transitions, leading to sudden qualitative and sometimes irreversible regime shifts [1, 2]. Because these transitions are often detrimental, the development of early warning signals is recognized as a major challenge [3]. Recent progress [4, 5, 6] builds on a mathematical framework in which the real-world system at hand is described by a low-dimensional equation system that captures the dynamics in terms of a small number of key variables. In this framework the critical transition often corresponds to a bifurcation. Here we show that in highdimensional systems, containing many variables, we frequently encounter an additional non-bifurcative mechanism that can lead to critical transitions. We develop a simple and intuitive early warning sign and illustrate both, mechanism and warning sign, in a range of examples, including network models of epidemics [7] and cooperation [8] and epidemiological data [9, 10]. This work thus establishes a connection between critical transitions and network science and provides an early warning sign for a new type of critical transition that could be relevant for many real world systems. In particular, in the light of the perspective to move to more complex models and utilize big data sources it can be anticipated that this new type of transition will be encountered frequently in the future.
Clean Technologies and Environmental Policy, 2014
The broad implications of catastrophic regime shifts have prompted the need to find methods that are not only able to detect regime shifts but more importantly, identify them before they occur. Rising variance, skewness, kurtosis, and critical slowing down have all been proposed as indicators of impending regime shifts. However, these approaches typically do not signal a shift until it is well underway. Further, they have primarily been used to evaluate simple systems; hence, additional work is needed to adapt these methods, if possible, to real systems which typically are complex and multivariate. Fisher information is a key method in information theory and affords the ability to characterize the dynamic behavior of systems. In this work, Fisher information is compared to traditional indicators through the assessment of model and real systems and identified as a leading indicator of impending regime shifts. Evidenced by the great deal of activity in this research area, it is understood that such work could lead to better methods for detecting and managing systems that are of significant importance to humans. Thus, we believe the results of this work offer great promise for resilience science and sustainability.
Frontiers in Environmental Science, 2014
Recently, Early Warning Signals (EWS) have been developed to predict tipping points in Earth Systems. This discussion highlights the potential to apply EWS to human social and economic systems, which may also undergo similar critical transitions. Social tipping points are particularly difficult to predict, however, and the current formulation of EWS, based on a physical system analogy, may be insufficient. As an alternative set of EWS for social systems, we join with other authors encouraging a focus on heterogeneity, connectivity through social networks and individual thresholds to change.
Early warning signals (EWS) are statistical indicators that a rapid regime shift may be forthcoming. Their development has given ecologists hope of predicting rapid regime shifts before they occur. Accurate predictions, however, rely on the signals being appropriate to the system in question. Most of the EWS commonly applied in ecology have been studied in the context of one specific type of regime shift (the type brought on by a saddle-node bifurcation, at which one stable equilibrium point collides with an unstable equilibrium and disappears) under one particular perturbation scheme (temporally uncorrelated noise that perturbs the net population growth rate in a density independent way). Whether and when these EWS can be applied to other ecological situations remains relatively unknown, and certainly underappreciated. We study a range of models with different types of dynamical transitions (including rapid regime shifts) and several perturbation schemes (density-dependent uncorrel...
Complex systems inspired analysis suggests a hypothesis that financial meltdowns are abrupt critical transitions that occur when the system reaches a tipping point. Theoretical and empirical studies on climatic and ecological dynamical systems have shown that approach to tipping points is preceded by a generic phenomenon called critical slowing down, i.e. an increasingly slow response of the system to perturbations. Therefore, it has been suggested that critical slowing down may be used as an early warning signal of imminent critical transitions. Whether financial markets exhibit critical slowing down prior to meltdowns remains unclear. Here, our analysis reveals that three major US (Dow Jones Index, S&P 500 and NASDAQ) and two European markets (DAX and FTSE) did not exhibit critical slowing down prior to major financial crashes over the last century. However, all markets showed strong trends of rising variability, quantified by time series variance and spectral function at low frequencies, prior to crashes. These results suggest that financial crashes are not critical transitions that occur in the vicinity of a tipping point.
The American Journal of Psychology, 2011
Scientific Reports
Tipping point dynamics are fundamental drivers for sustainable transition pathways of social-ecological systems (SES). Current research predominantly analyzes how crossing tipping points causes regime shifts, however, the analysis of potential transition pathways from these social and ecological tipping points is often overlooked. In this paper, we analyze transition pathways and the potential outcomes that these may lead to via a stylized model of a system composed of interacting agents exploiting resources and, by extension, the overall ecosystem. Interactions between the social and the ecological system are based on a perception-exploitation framework. We show that the presence of tipping points in SES may yield counter-intuitive social-ecological transition pathways. For example, the high perception of an alarming ecological state among agents can provide short-term ecological benefits, but can be less effective in the long term, compared to a low-perception condition. This work...
Environment: Science and Policy for Sustainable Development, 2010
Ecology and Society, 2015
Recent global crises reveal an emerging pattern of causation that could increasingly characterize the birth and progress of future global crises. A conceptual framework identifies this pattern's deep causes, intermediate processes, and ultimate outcomes. The framework shows how multiple stresses can interact within a single social-ecological system to cause a shift in that system's behavior, how simultaneous shifts of this kind in several largely discrete social-ecological systems can interact to cause a far larger intersystemic crisis, and how such a larger crisis can then rapidly propagate across multiple system boundaries to the global scale. Case studies of the 2008-2009 financial-energy and food-energy crises illustrate the framework. Suggestions are offered for future research to explore further the framework's propositions.
Ecology and Society, 2020
There are many calls to use the COVID 19 crisis as an opportunity for transforming to a future trajectory that is more equitable and environmentally sustainable. What is lacking is a cohesive framework for bringing these calls together. We propose that such transitions could be informed by lessons from three decades of scholarship on abrupt and surprising change in systems of humans and nature. Over time, many social-ecological systems exhibit cycles of change consisting of sequential patterns of growth, development, crisis, and reorganization. A critical phase in the cycle is the brief period after crisis when novelty and innovation can change the future trajectory. Without being prepared for this window of opportunity, deep, systemic change may be unachievable. We propose a three-step process to identify the major drivers of the global system that need to be changed: (1) identifying what society values; (2) identifying the determinants of these valued variables; and (3) identifying the underlying drivers of the determinants and how they need to be changed. A tentative list of five such drivers are identified and discussed: (i) the economic system, (ii) homogenization, (iii) human population growth, size, and densities, (iv) consumption patterns, human ethics, and behavior, and (v) governance. They are linked to seven questions relating to how we might proceed in addressing the drivers. If response to the crisis merely reinforces the existing system, its incompatibility with the natural world and its propensity to increase inequity and conflict will likely increase fragility and lead to another version of the present calamity. If it is a deliberately transformed system that emerges its future will depend on the reorganization process, and the way the system is guided into the future. What is needed is a deliberate, fundamental cultivation of emergence to enable transformation toward better futures in order to avoid an inevitable deepening of a system that ultimately is worse for all.
Complexity, 2018
Social systems are always exposed to critical processes in which their organization, or part of it, is questioned by the society that demands solutions through different critical saliences. The traditional approach to such social crises has mainly focused on their anticipation and management, implying that the focus is on trying to deal with crises once they occur, rather than delving in their essential characteristics that seemingly depend on the adaptive nature of the system and the increase in its internal complexity. To address this issue, we propose a dual approach that utilizes both qualitative (documentary analysis) and quantitative methods (online social network analysis) in order to delve into the relationship between the complexity of the social system, its adaptation, and critical episodes. Our analysis shows how an explosive economic growth affects a social system, increasing its complexity. This complexity produces different demands from the system itself. These demands...
Bulletin of Mathematical Biology, 2018
Many complex systems exhibit critical transitions. Of considerable interest are bifurcations, small smooth changes in underlying drivers that produce abrupt shifts in system state. Before reaching the bifurcation point, the system gradually loses stability ('critical slowing down'). Signals of critical slowing down may be detected through measurement of summary statistics, but how extrinsic and intrinsic noises influence statistical patterns prior to a transition is unclear. Here, we consider a range of stochastic models that exhibit transcritical, saddle-node and pitchfork bifurcations. Noise was assumed to be either intrinsic or extrinsic. We derived expressions for the stationary variance, autocorrelation and power spectrum for all cases. Trends in summary statistics signaling the approach of each bifurcation depend on the form of noise. For example, models with intrinsic stochasticity may predict an increase in or a decline in variance as the bifurcation parameter changes, whereas models with extrinsic noise applied additively predict an increase in variance. The ability to classify trends of summary statistics for a broad class of models enhances our understanding of how critical slowing down manifests in complex systems approaching a transition.
International Journal of Forecasting, 2014
What do the behavior of monkeys in captivity and the financial system have in common?
2015
We investigate the effects of complex social network interactions on social regime shifts within a coupled socioecological system. We observe the occurrence of hysteresis between the cooperative and defective regime as we vary the resource inflow within the system. As we adjust the social network properties such as degree and topology, we notice a change in the width of the hysteresis curve. This result signifies the intimate connection between the underlying structure of the social interactions and the resiliency of the coupled socio-ecological system. In particular, we uncover a new feature of multiple regime shifts within the hysteresis curve as we introduce community structures into the complex social interactions, indicating that the presence of sub-structures in the interactions can break up the collapse or revival of a full regime shifts into multiple smaller regime shifts. Furthermore, we highlight the possibilities of making accurate early warning detections on the occurren...
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