Cascading regime shifts within and across scales
Rocha et al.

Regime shifts are large, abrupt and persistent critical transitions in the function and structure of systems. Yet it is largely unknown how these transitions will interact, whether the occurrence of one will increase the likelihood of another, or simply correlate at distant places. Here we explore two types of cascading effects: domino effects create one-way dependencies, while hidden feedbacks produce two-way interactions; and compare them with the control case of driver sharing which can induce correlations. Using 30 regime shifts described as networks, we show that 45% of the pair-wise combinations of regime shifts present at least one plausible structural interdependence. Driver sharing is more common in aquatic systems, while hidden feedbacks are more commonly found in terrestrial and Earth systems tipping points. The likelihood of cascading effects depends on cross-scale interactions, but differs for each cascading effect type. Regime shifts should not be studied in isolation: instead, methods and data collection should account for potential teleconnections.

Minimal examples of the cascading effects. We merged pairs of regime shifts causal networks and created a response variable matrix that accounted for drivers shared, domino effects, or hidden feedbacks for all pair-wise combinations of regime shifts. For example, for drivers sharing two minimal regime shifts are depicted as causal diagrams, drivers are coloured red and variables inside feedbacks purple. The joint network is represented as a 2-mode network which allows us to study the co-occurrence of drivers across regime shifts. The response variable matrix counts the drivers shared by all pair-wise combinations of regime shifts. In the example of a domino effect two regime shifts are joined together where driver c in regime shift 2 is part of a feedback process in regime shift 1, creating a one-way dependency (orange colored link) between the two regime shifts. The response variable matrix counts all the one-way causal pathways between pair-wise combinations of regime shifts. In the example of a hidden feedback, two minimal regime shifts when joined together give rise to a new unidentified feedback of length 4 (orange circular pathway). The response variable matrix counts all hidden feedbacks that arise when merging all pair-wise combinations of regime shifts. Labelled matrices of the resulting response variables are available in the supplementary material.

Driver sharing. The distribution of drivers shared per regime shift (a) with respect to the number of drivers each one has (black points) shows that regime shifts in aquatic environments tend to have and share more drivers. (b) shows the drivers most shared. WAIS abbreviates West Antarctica Ice Sheet collapse.

https://www.biorxiv.org/content/10.1101/364620v1

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