MEPS 512:99-113 (2014)  -  DOI: https://doi.org/10.3354/meps10909

ABSTRACT: Ecological thresholds, associated with abrupt changes in the state and organisation of ecosystems, challenge both scientists and managers. Adaptive response to such changes, and planning for their occurrence, requires an understanding of the underlying drivers and system responses as well as appropriate monitoring. In addition to field studies, modelling can advance our ability to anticipate or deal with such major ecosystem shifts. Here, we used an existing multispecies model with smooth continuous functions that were modified to include thresholds representing 3 alternative scenarios of predator responses when prey numbers drop below a critical threshold: (I) no threshold-like response; (II) an abrupt decrease in breeding success by 90%, and (III) an abrupt halving of adult survival. Second, we analysed field observations from 3 independent marine case studies (abalone, starfish, penguins) for evidence of abrupt non-linear responses of predators to changes in abundance of principal prey. Third, we compared the model output with empirical results and tested (using both a statistical method and by fitting multispecies models) the 3 alternative response scenarios. With this approach, we found evidence for nonlinear changes in population parameters (such as survival rate) of predators as prey numbers declined below critical thresholds. As an example of the potential for this approach to inform management, we found that abundances of a range of marine predators become more variable as prey numbers decline, which may be a useful indicator that a system is approaching a tipping point.

KEY WORDS: Abrupt change · Ecological thresholds · Adaptive management · Trophodynamics · Intermediate complexity model · Non-linear responses

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Cite this article as: Plagányi ÉE, Ellis N, Blamey LK, Morello EB and others (2014) Ecosystem modelling provides clues to understanding ecological tipping points. Mar Ecol Prog Ser 512:99-113. https://doi.org/10.3354/meps10909 Export citation Share:    Facebook - - linkedIn