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Marine Ecology Progress Series

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

Ecosystem modelling provides clues to understanding ecological tipping points

Éva E. Plagányi1,*, Nick Ellis2, Laura K. Blamey3, Elisabetta B. Morello2, Ana Norman-Lopez1, William Robinson4, Miriana Sporcic1, Hugh Sweatman5

1Climate Adaptation and Wealth from Oceans Flagship, CSIRO, PO Box 2583, Brisbane, QLD 4001, Australia
2Wealth from Oceans Flagship, CSIRO, PO Box 2583, Brisbane, QLD 4001, Australia
3Marine Research (MA-RE) Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
4Marine Resource Assessment and Management, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
5Australian Institute of Marine Science, PMB3, Townsville MC, QLD 4810, Australia
*Corresponding author:

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

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