Our experience in understanding ecosystem dynamics and managing threats is being applied to help reduce the threat to the Great Barrier Reef from predation by Crown-of-thorns starfish.

The challenge

Crown-of-thorns starfish threaten the Reef’s survival

The Great Barrier Reef is under severe pressure from a number of factors, including deteriorating water quality, cyclones, rising water temperatures and increasing ocean acidification due to climate change, as well as a major predator of corals, the Crown-of-thorns starfish (CoTS).

Initial coral cover on the Great Barrier Reef declined by about 50 per cent over the 30 years to 2012 and has continued to decline since that time. CoTS, which feed on hard corals, were responsible for almost half of the decline to 2012 (De’ath et al., 2012). Along with cyclones and bleaching, CoTS remain a key threat to hard corals on the reef and, therefore, a threat to the health and future of this ecologically, economically and culturally important Australian ecosystem.

Responding to the threat posed by CoTS requires that we:

  • understand the causes of CoTS outbreaks and use this understanding to prevent future outbreaks
  • design and implement management strategies that prevent or reduce the spread of existing outbreaks and which promote coral recovery.

Our response

Using ecological modelling to inform CoTS management

Crown-of-thorns starfish feeding on the last living hard corals at a site on Rib Reef, Great Barrier Reef, in January 2018.

We are leading a number of projects funded through the National Environmental Science Programme (NESP) Tropical Water Quality Hub aimed at managing the CoTS threat.

We have developed detailed ecological models to identify and describe key population and process thresholds and parameters associated with CoTS outbreaks in order to inform management decision making. These include spawning densities and thresholds for CoTS outbreaks and coral recovery.

We have also used mathematical modelling to combine detailed ecological, water quality and oceanographic data to test hypotheses for the causes of CoTS outbreaks.

Applying ecological and environmental management expertise

Effective management of CoTS outbreaks, now and in the future, requires that our management strategy design takes into account the spatial and temporal dynamics of CoTS outbreaks on the GBR, as well as the capacity and the constraints under which the control program operates. This is a complex and multi-layered problem and effective solutions require that we deal with vast areas, complex and difficult habitats, and the need to address the issues at a variety of levels simultaneously.

With funding from the NESP Tropical Water Quality Hub, and working with partners that span the entire breadth of the CoTS issue, we designed a national research strategy for managing the impact of CoTS on the Great Barrier Reef. The strategy draws on the collective experience of CoTS control operations, policy makers, and researchers to generate relevant, on-water management recommendations from established research.

Our goal is to improve the performance of the control program, both in terms of the on-water operations and the strategic decision making that guides those operations.

The team includes experts from the Association of Marine Park Tourism Operators, the Great Barrier Reef Marine Park Authority, the Department of Environment and Energy, and researchers from the Australian Institute of Marine Sciences, James Cook University, the University of Sydney and the University of Queensland.

The results

Improved knowledge and management outcomes

The project group has made some significant advances in a variety of areas:

  • developed a surveillance component for the control program, which was implemented with the support of the control program staff, and is estimated to have improved efficiency by 33 – 55% within existing budgets. This success has led to strong stakeholder support and additional funding to address this problem at regional scales.
  • identified knowledge that are gaps preventing improved control of CoTS and implemented a staged approach to filling those gaps
  • developed oceanographic models to predict dispersal of CoTS and coral larvae and from this to predict the reefs that are most at risk
  • developed decision support tools to allow flexible and strategic decisions about where and how much control effort to invest
  • described the movement potential of CoTS, allowing for improved modelling of recolonization of CoTS populations after control
  • developed data collection protocols and data entry and display tools to ensure that high quality data on the control program and its performance is being collected in order to allow assessment and improvement.

Reports and further information about the NESP projects are available:

Project 1.1: Establishing the future NESP CoTS research framework including an ecologically-based approach to the management of CoTS at multiple scales

Project 2.1.1: Integrated Pest Management of Crown-of-Thorns Starfish

Project 3.1.1: Implementation of the Crown-of-thorns research strategy: regional strategies

Project 4.1: Crown-of-thorns starfish: surveillance and life history

Interested in helping us further this research?

We seek research collaborators with complementary skills so we can work together for stronger results.

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