eCite Digital Repository

Exploring ecological shifts using qualitative modelling: Alternative states on Tasmanian rocky-reefs


Marzloff, MP and Dambacher, J and Little, R and Frusher, SD and Johnson, CR, Exploring ecological shifts using qualitative modelling: Alternative states on Tasmanian rocky-reefs, 18th World IMACS / MODSIM Congress, 13-17 July 2009, Cairns, Australia, pp. 2143-2149. (2009) [Refereed Conference Paper]

Copyright Statement

Copyright 2009 The Modelling and Simulation Society of Australia and New Zealand Inc. and the International Association for Mathematics and Computers in Simulation

Official URL:


Alternative stable states characterise many natural ecosystems. Subtidal rocky-reefs on the east coast of Tasmania persist in a range of different configurations, including so-called sea urchin ‘barrens’ and dense seaweed beds with a closed canopy. In creating and maintaining barrens habitat on temperate reefs, sea urchins induce major losses of production, biodiversity and physical structure. The invasive long-spined sea urchin (Centrostephanus rodgersii) is able to form barrens across its newly extended range in Tasmania. Formation of urchin barrens on the east coast has been a rising concern in recent decades, in particular because the two most valuable fisheries in the state, for blacklip abalone (Haliotis rubra) and southern rock lobster (Jasus edwardsii), are not viable on barrens. Thus, identifying triggers of barrens formation is critical in the management of these reefs. Here we explore the dynamics of Tasmanian rocky-reef communities, including testing the effects of fishing, using qualitative modelling informed by a deep empirical knowledge of interactions among species. Loop analysis offers a holistic approach to address the structure and dynamics of the system. It sacrifices precision of particular dynamics to maximize reality and generality in providing a causal understanding of complex systems. The network topology forms emergent feedback patterns that cause meta-stable properties in this rocky-reef system, and the models capture formation of urchin barrens and the mechanisms of the phase shifts. Fishing is identified as a perturbation that can reduce resilience of the system in its original highly productive seaweed-dominated state. We show that qualitative loop models can be highly valuable in identifying the kinds of system dynamics that managers need to consider in ecosystem based management, but emphasise that they are not designed to act as definitive management models for specific instantiations.

Item Details

Item Type:Refereed Conference Paper
Keywords:qualitative modelling of feedback; alternative persistent states in ecological dynamics; rocky reef community structure; Tasmania; rock lobster; sea urchin barrens
Research Division:Environmental Sciences
Research Group:Ecological applications
Research Field:Ecosystem function
Objective Division:Environmental Management
Objective Group:Terrestrial systems and management
Objective Field:Assessment and management of terrestrial ecosystems
UTAS Author:Marzloff, MP (Dr Martin Marzloff)
UTAS Author:Frusher, SD (Professor Stewart Frusher)
UTAS Author:Johnson, CR (Professor Craig Johnson)
ID Code:87804
Year Published:2009
Deposited By:IMAS Research and Education Centre
Deposited On:2013-12-09
Last Modified:2014-08-20

Repository Staff Only: item control page