Current Applications of The Regime Shift Concept
During the last decades, research on regime shift has grown exponentially. Academic papers reported by ISI Web of Knowledge rise from less than 5 per year prior to 1990 to more than 300 per year from 2007 to the 2011. However, the application of regime shift related concepts is still contested.
Although there is not agreement on one definition, the slight differences among definitions reside on the meaning of stability -the measure of what a regime is- and the meaning of abruptness. Both depend on the definition of the system under study, thus it is relative. At the end it is a matter of scale. Mass extinctions are regime shifts on the geological time scale, while financial crises or pest outbreaks are regime shifts that require a totally different parameters setting.
In order to apply the concept to a particular problem, one has to conceptually limit its range of dynamics by fixing analytical categories such time and space scales, range of variations and exogenous / endogenous processes. For example, while for oceanographers a regime must last for at least decades and should include climate variability as a driver, for marine biologists regimes of only five years are acceptable and could be induced by only population dynamics. A non-exhaustive range of current definitions of regime shifts in recent scientific literature from ecology and allied fields is collected in Table 1.
Table 1. Definitions of regime shifts and modifications used to apply the concept to particular research questions from scientific literature published between 2004-2009.
| Source | Definition | Modification |
|---|---|---|
| Collie et al. 2004 | “Three different types of regime shift (smooth, abrupt and discontinuous) are identified on the basis of different patterns in the relationship between the response of an ecosystem variable (usually biotic) an some external forcing or condition (control variable). The smooth regime shift is represent by a quasi-linear relationship between the response and control variables. The abrupt regime shift exhibits a nonlinear relationship between the response and control variables, and the discontinuous regime shift is characterized by the trajectory of the response variable differing when the forcing variable increases compared to when it decreases (i.e., the occurrence of alternative “stable” states)” | “”Regime shifts” are considered here to be low-frequency, high-amplitude changes in oceanic conditions that may be especially pronounced in biological variables and propagate through several trophic levels” |
| Bakun 2004 (in Collie et al. 2004) | “persistent radical shift in typical levels of abundance or productivity of multiple important components of marine biological community structure, occurring at multiple trophic levels and on a geographical scale that is at least regional in extent” | |
| Walker & Meyers, 2004 | "A regime shift involving alternate stable states occurs when a threshold level of a controlling variable in a system is passed, such that the nature and extend of feedbacks change, resulting in a change of direction (the trajectory) of the system itself. A shift occurs when internal processes of the system (…) have changed and the state of the system begins to change in a different direction, toward a different attractor." | |
| Andersen et al. 2009 | “ecological regime shifts can be defined as abrupt changes on several trophic levels leading to rapid ecosystem reconfiguration between alternative states” | |
| Cumming & Norberg, 2008 | "the ability of a system to internally switch between different self reinforcing processes that dominate how the system functions" | |
| Brock, Carpenter and Scheffer 2008 (Chap 6 in Cumming and Norberg) | “Regime shifts, substantial reorganizations of complex systems with prolonged consequences In environmental policy regime shifts raise the prospect that incremental stresses may evoke large, unexpected changes in ecosystem services and human livelihoods” | |
| Biggs et al. 2009 | “Ecological regime shifts are large, sudden changes in ecosystems that last of substantial periods of time Regime shifts entail changes in the internal dynamics and and feedbacks of an ecosystem that often prevent it from returning to a previous regime, even when the driver that precipitated the shift is reduced or removed Regime shifts typically result from a combination of gradual changes in an underlying driving variable (or set of variables), combined with an external shock, such as a storm or fire” | “We defined a regime shift as the period over which the annual increase in the planktivore (F) population exceeded 10%. In the model, regime shifts have a typical duration of ≈15 years, reflecting plausible limits on the growth rate of F” |
| Norström et al. 2009 | “Certain conditions may ultimately result in persistent alternative stable states (ASS), which are characterized by a different set of ecosystems processes, functions and feedback mechanisms...” | “we defined phase shifts as an extensive decreases in coral cover coinciding with substantial increases in some alternative benthic organism, due to a pulse or press disturbance, that have persisted >5yr. A minimum persistence time of 5 yr was used, as this is in accordance with the timeframe of studies describing cases of phase shifts from coral to macroalgal states...” |
| Scheffer (2009) | “a relatively sharp change from one regime to a contrasting one, where a regime is a dynamic ‘state’ of a system with its characteristics stochastic fluctuations and/or cycles” |
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