Turning back from the brink: Detecting an impending regime shift in time to avert it

Publication review

New research on the potential for averting regime shifts.

In the PNAS-article entitled Turning back from the brink: Detecting an impending regime shift in time to avert it, centre-affiliated researcher Reinette “Oonsie" Biggs, Stephen R. Carpenter and William A. Brock investigated whether new early warning indicators of regime shifts may provide sufficient warning to take action to avert undesirable regime shifts.

Promising new indicators
Regime shifts are notoriously difficult to predict. They often come as a surprise, and by the time society realizes what is happening it is often too late or too costly to reverse the changes.

However, society´s ability to anticipate regime shifts may be improving. Recent research indicates that changes in ecological time series (such as increased variability) can provide early warning of impending regime shifts.  

- Work is underway to improve these new indicators and to test them in actual field settings. However, no one has yet answered the question of whether such indicators would provide sufficient warning to allow the implementation of management actions to avoid undesirable regime shifts, says Biggs.

Biggs, Carpenter and Brock used a fisheries food web model to investigate this question. They explored how close an ecosystem can get to an ecological threshold and still avert a regime shift by implementing management changes. The model was also used to find out which indicators might give warning before a “point of no return", where it is too late to take action to avert an undesirable regime shift.

Rapid response is essential
The results from the model showed that if the factor responsible for a regime shift can be rapidly altered (e.g. fishing pressure), successful management action to avert a regime shift may be delayed until a regime shift is underway. However, if the driver can only be manipulated gradually (e.g. shoreline habitat restoration) management action is needed substantially before a regime shift in order to avert it.

The challenge is that large increases in the indicators (which serve as warning of an impending regime shift) only show up once a regime shift is initiated. This means that the current indicators will only be useful in averting regime shifts if 1) the factor driving the regime shift can be rapidly manipulated, and 2) if management action is taken very rapidly as soon as the indicators start flashing their warning lights.

In cases where the factor driving the regime shift can only be gradually manipulated, the indicators will usually give warning too late to allow management action to avert the regime shift.  

To improve their usefulness in averting regime shifts, Biggs et al. suggest that future research focus on defining critical indicator levels at which management action should be taken rather than detecting change in the indicators.

More proactive decision-making processes needed
Averting ecological regime shifts does not simply require better indicators, but is also dependent on developing policy processes that enable society to respond more rapidly to warnings of impending regime shifts.

- Our results highlight that in systems subject to regime shifts there is often a discrete window for policy action, after which it becomes impossible to advert a shift, says Biggs.

By the time adverse environmental effects become apparent it is often too late to avert a regime shift. Trial-and-error approaches that wait for evidence of negative environmental impacts before taking action are therefore ill-advised.  

The results from the research underscore the need for developing decision-making approaches that enable proactive intervention in averting ecological regime shifts.