OOS 9-4 - Regime shift interruptus: When do we act?

Tuesday, August 4, 2009: 9:00 AM
Blrm A, Albuquerque Convention Center
Aaron M. Ellison, Harvard Forest, Harvard University, Petersham, MA
Background/Question/Methods

Rapid progress has been made in identifying leading indicators for regime shifts in a wide variety of ecological systems and contexts. For these leading indicators to be most useful, we also need to know how far in advance, and at what cost, interventions should occur to minimize the probability of an undesirable regime shift or to maximize the probability of a desirable one. I explored various management approaches (“business-as-usual”, “rapid-and-aggressive”, and those in between) and cost-benefit analyses to simulation models of three ecological systems approaching regime shifts – grasslands under different burning and grazing management; oceanographic/climatic changes in Atlantic circulation; and Carpenter’s model of lake eutrophication. For each model, I determined how far in advance (in simulated years) a leading indicator (change in the high frequency signal in the spectral density of the modeled time series) could detect the impending regime shift. I then applied the different management approaches to the model at a range of times working backwards from the actual time of the regime shift to the time when all regime shifts could be averted. Rough costs of action were estimated based on type and duration of management interventions.
Results/Conclusions

Simulations suggest that even under the most optimistic, “rapid-and-aggressive” scenarios, management interventions need to be applied > 20 years before an impending regime shift in order to avert it. Socioeconomic constraints, political horse-trading, and short-term planning all contribute to slower and more limited management interventions that must be applied even further in advance (up to 50 years) to avoid regime shifts with negative ecological consequences. Such slower or “business-as-usual” responses have low up-front costs but large long-term (inter-generational) costs. Judicious application of the precautionary principle can reduce the probability of future regime shifts, but its application also can limit opportunities for adaptive management or additional experimentation to determine overall behavior of systems that are nearing regime shifts. Future work on detection and management of regime shifts should begin by assembling a range of stakeholders and analysts from a broad range of disciplines and focus on a combination of adaptive experimentation to determine drivers of regime shifts and effective and providing realistic sociocultural solutions to manageme regime shifts and simultaneously preserve ecological integrity.

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