1. Polycrises of the present and past

Increasing awareness exists among academics, policy analysts, and the public that we are experiencing a global ‘polycrisis': a series of interconnected and interacting threats—climate change and ecological disasters, rising economic inequality and political polarization, violent conflict and more (cf. [1]). While the scale and global synchrony of these threats present novel challenges, these types of stressors have been an inherent part of the human experience, and have at times converged with other socio-cultural pressures; there have been polycrises in the past as today.

Analyses of our current polycrisis often overlook lessons offered by historical examples, while scholarship exploring past environmental crises typically converges on a few well-known cases of severe stress contributing to apparent societal collapse [2–8]. These studies generally focus on a single event or particular social formation, seeking to establish temporal correlations between environmental hazards and major societal transformations. While the resulting findings are of intrinsic interest, they typically do not offer insights generalizable to multiple cases from different regions and periods.1 Further, while the transformations often associated with collapse are frequently presented as the extreme outcome of ‘failures' to adapt or develop resilience against challenges, such ‘collapses’ may themselves be considered powerful adaptations required to replace maladaptive or otherwise vulnerable systems with more resilient ones. A positive development has been a recent surge in work across and between disciplines—anthropology, environmental and biophysical science, sociology, history, among others—attempting to grapple with the inherent complexity of contemporary and historical human–environmental relations, highlighting the diversity of societal responses to adverse climate and ecological shocks (cf. [12–15]). Such work has identified many open questions, not least about societal and environmental interactions at different temporal and spatial scales: why, for instance, do large-scale climate events tend to produce divergent outcomes among different societies? What are the principal forces underpinning social vulnerability? Also, why do social systems seem to oscillate between sustainability and vulnerability over long time periods?...

.... have systematically collected information about the character and consequences of over 150 past societal crises covering multiple world regions at different historical periods.3 Figure 1 illustrates the wide range of outcomes experienced by past societies. These range from more severe cases where multiple destabilizing events overlap (uprisings, civil war, mass mortality, societal collapse or fragmentation) to less disruptive examples wherein ruling classes are targeted (assassinations, elite extermination) or where only a few events co-occur,4 to a few cases where none of these happen or are not attested in the available sources.

Figure 1. Number of cases in the CrisisDB historical sample experiencing different types of unrest and instability (n = 169). Severity of consequences are calculated as a cumulative total of 13 possible outcomes. See the electronic supplementary material for details.