The term ‘polycrisis’ has gained widespread currency in discussions of global affairs (e.g. Davies & Hobson, Reference Davies and Hobson2022; Tooze, Reference Tooze2022, Reference Tooze2021; UNDP, 2022; WEF, 2023). Its popularity suggests that a growing number of people believe that the world's multiple interacting crises require new ways of thinking and acting. Established approaches that address crises individually cannot contend with their increasing interconnections. But the term ‘polycrisis’ has been used in such loose and haphazard ways that it is sometimes dismissed as a counter-productive buzzword (e.g. Drezner, Reference Drezner2023; Kluth, Reference Kluth2023). While many scholars and commentators hope this new concept will generate insights, strategies, and policies that better address humanity's interwoven challenges, how it can do so remains unclear.

In the article ‘Global Polycrisis: The Causal Mechanisms of Crisis Entanglement’ (the lead article of this special issue), my co-authors and I provide substance to the polycrisis concept. The article develops a theoretical framework for polycrisis analysis and proposes an urgent polycrisis research agenda.

We define a global polycrisis as the causal entanglement of crisis in multiple global systems in ways that significantly degrade humanity's prospects. The combined harms of these entwined crises are both different than and generally greater than those the crises would produce in isolation from one another. And because it has no single underlying cause, a polycrisis requires strategies that are multi-disciplinary, systemic, and cross-sectoral, as efforts to reduce one problem can easily worsen others.

On this conceptual foundation, our framework makes three major contributions, each of which requires further scrutiny and development. After elaborating upon these three moves, I introduce three prominent debates in the growing commentary around the polycrisis concept and highlight ways in which these debates suggest promising research directions for polycrisis analysis. This commentary ultimately aims to stimulate others to contribute to the special issue ‘Polycrisis in the Anthropocene’ and help develop the field of polycrisis analysis.

1. (1) Crisis as systemic disequilibrium

In the first analytical move of our ‘Global Polycrisis’ article, my colleagues and I use critical transitions theory to propose a systems-based conceptualization of global crises. In many natural and social systems, gradual change in a key system parameter (what we call a systemic ‘stress’) erodes the feedbacks that keep the system in one dynamic equilibrium (a familiar range of properties), so that the system abruptly flips to a new equilibrium with a different set of functions, behaviors, characteristics, and feedbacks (Scheffer, Reference Scheffer2009; Scheffer et al., Reference Scheffer, Carpenter, Lenton, Bascompte, Brock, Dakos, van de Koppel, van de Leemput, Levin, van Nes, Pascual and Vandermeer2012).

A system that has left one equilibrium, however, may not immediately settle into a new equilibrium. It is this volatile interregnum that we define as a systemic crisis: an incomplete critical transition in which a global system (such as food, environment, economy, energy, security, governance, transportation, communication, or health) has left one dynamic equilibrium but not yet settled into another (nor returned to its former equilibrium) and is therefore in an unstable state of disequilibrium that generates significant human harms.

For some, this conceptualization is counterintuitive because it focusses on global systems as the entities that go into crisis (i.e. out of equilibrium) rather than those entities more commonly declared to be ‘in crisis’, such as a person, a nation, a market, or the world. By our definition, however, systemic disequilibrium must create harms for these more familiar referents to qualify as a systemic crisis.

In the current geopolitical crisis, for example, the former (albeit weak) consensus among major powers regarding the basic rules of world order – including the prohibition of international aggression, the nuclear taboo, broadly acknowledged hierarchies, and settled spheres of influence – has broken down; major powers now pursue conflicting visions of world order in an era of great technological, ecological, and social transformation. Though often characterized as crises, Russia's invasion of Ukraine and China's regional assertiveness represent, in our framework, manifestations of this more profound systemic crisis. The geopolitical system is out of equilibrium, generating instability, surprises, conflict, and major suffering.

The value-added of this conceptualization is threefold. First, characterizing crisis as systemic disequilibrium captures the non-linear character of crisis as an abrupt break from normalcy. In a pattern of ‘punctuated equilibrium’, systems get locked-in to a set of arrangements and behaviors for long periods of time, until they reach a ‘critical juncture’ at which existing structures break down and radical change becomes possible (Gould & Eldredge, Reference Gould and Eldredge1993; Pierson, Reference Pierson2004). As Vladimir Lenin once observed, ‘There are decades where nothing happens; and there are weeks when decades happen’. Our notion of systemic crisis helps explain the unevenness of change.

Second, our conceptualization of systemic crisis helps to distinguish between harms that arise from the normal functioning of a system and those that arise from the sudden disruption of normal system functioning – that is, from systemic crisis. Nineteenth century imperialism, for example, generated immense human harms, but through the regular functioning of European-dominated geopolitical and economic systems. The Second World War and the struggles for national liberation that followed also created immense human harms – but these harms stemmed from crises in those systems. Global geopolitical and economic systems eventually transitioned to a new equilibrium that included an explosion of (de jure but often not de facto) independent states, the Bretton Woods institutional order, and informal imperialism (Duara, Reference Duara2011; Galtung, Reference Galtung1971; Westad, Reference Westad2005). And this new equilibrium generated its own patterns of harms (such as proxy wars and crippling international debts) through its normal functioning.

Finally, the conceptualization of crisis as an incomplete critical transition raises specific, novel, and productive research questions about global crises:

• • What is the relevant system, where are its (albeit fuzzy, open, and shifting) boundaries, and how does it relate to other systems?

• • What range of states and behaviors constitute the normal functioning of a system's equilibrium?

• • What feedbacks once maintained an established equilibrium, and why did they cease to do so?

• • What events and behaviors indicate that a system is in a state of disequilibrium (i.e. in a systemic crisis)?

These questions can be investigated with a variety of methodologies, qualitative and quantitative. My colleagues and I believe that the answers can help inform new and more effective strategies for crisis prevention and response. They might also reveal the limitations of our systemic crisis approach insofar as it illuminates some problems and harms more than others. It is crucial to note here that any and every definition of ‘crisis’ has political implications concerning whose problems get attention, what sorts of actions are taken, and what harms are simply accepted or ignored.

1. (2) Stresses and triggers

With our second analytical move, we distinguish between the long-term stresses and fast-moving trigger events that interact with one another to push a system out of its equilibrium and into crisis. Stresses are slow-moving processes – such as increasing socio-economic inequality, climate heating, and demographic change – that gradually, over the course of years and decades, erode the resilience of a system's equilibrium. Triggers are fast-paced events – such as political uprisings, bankruptcies, or the extinction of a keystone species – that interact with stresses in timespans of seconds to weeks to push a system out of its equilibrium. Stresses create ‘systemic risks’ – possibilities for a problem in one part of a system to spread throughout the system, disrupt its overall functioning, and spill over into other systems (Renn et al., Reference Renn, Lucas, Haas and Jaeger2019). Trigger events activate those risks into cascading failures.

The distinction between stresses and triggers recognizes the multiple temporalities, scales, and causes of global crises. It is especially important because policymakers and publics alike tend to focus on the most immediate triggers of a crisis while paying too little attention to the underlying stresses that set a system up for disaster. For example, in 2023, amidst Canada's worst wildfire season on record, several politicians blamed the fires entirely on lightning strikes and irresponsible campers; they refused to acknowledge the significant role of climate change, which generated dangerously dry conditions and more frequent lightning strikes. Such ‘trigger fixation’ helps politicians shirk their responsibility to fight climate change and improve disaster prevention and response capacities; wildfires will likely grow even more devastating in the years ahead as a result (Lawrence & Homer-Dixon, Reference Lawrence and Homer-Dixon2023). The more stressed a system becomes, the more likely it is that some or other trigger event will come along and tip that system into crisis. Stresses lend trigger events their causal efficacy and therefore require close attention.

Wildfires are a fairly straightforward example, but distinguishing stresses, triggers, and crises from one another is seldom an easy task. The distinctions are often open to dispute and may (here as well) be counterintuitive. In Europe during the mid-2010s, for example, massive flows of refugees fleeing war in Syria acted, in our understanding, as the trigger of a systemic crisis in the human mobility system, as they overwhelmed camps, humanitarian responses, and borders, and suffered considerably. Underlying stresses included the economic inequality between the global north and south, unrepresentative government in the Middle East, the growth of populism and xenophobia in Europe, and the growing gap between contemporary patterns of migration and the capacities of the international migration regime.

This characterization of the European migration crisis (and other applications of the stress-trigger-crisis distinction) remains debatable. Yet historians and social scientists often make credible distinctions between structural (or ‘root’) causes and the proximate causes of significant historical episodes (such as crises). These disciplines show that diligent investigation can make defensible distinctions like those we draw in our polycrisis framework.

1. (3) Causal mapping (Domino effects and feedback loops):

Our third analytical contribution is to use stresses, triggers, and systemic crises as the elements of two types of causal maps that trace possible pathways through which global crises can emerge and interact with one another. ‘Domino diagrams’ depict the causal relationships between stresses, triggers, and crises in multiple systems as they unfold over time. The left-to-right temporal logic of these diagrams forms a causal timeline, but relationships can, consequently, only go in one direction. ‘Inter-systemic feedback diagrams’ capture the cyclical and synchronous relationships between stresses, triggers, and crises, wherein effects influence their own causes and thereby create feedback loops (for other insightful applications of causal loop diagrams, see Richards et al., Reference Richards, Lupton and Allwood2021; Thalheimer et al., Reference Thalheimer, Gaupp and Webersik2023).

By highlighting relationships between systems that are usually addressed in silos, these causal maps help reveal the processes by which crises cascade and amplify as they entangle multiple systems into a polycrisis. And where the literature on catastrophic and existential risk often focuses on threats that are (or are treated as) exogenous to global systems (such as an asteroid collision, or the emergence of super-intelligent artificial intelligence), these causal maps help to endogenize global crises within the internal workings of, and interactions between, global systems. They can help us understand how systems develop rigidities, gain and lose resilience, and create systemic risks as they grow more complex and interconnected.

To be valid and useful, however, such diagrams must make justified causal inferences about the relationships among elements. Many different methods and data sources can be used, but good causal mapping requires additional guidance to gauge the reliability of causal claims, especially as we apply polycrisis analysis to urgent policy challenges. Some of the causal relationships depicted in diagrams of the ‘Global Polycrisis’ article (such as the causes of the Covid-19 pandemic) are well-established in the scientific literature; others (such as the relationship between extreme weather events, mass climate migration, and violent conflict) remain more speculative. And our diagrams, finally, depict only positive feedbacks; the next step is to incorporate the dampening relationships and negative feedbacks that might counteract or restrain the self-reinforcing dynamics of polycrisis.