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Modelling ecosystem complexity

Ecosystem wide implications of reintroductions


Conservation management sometimes requires introducing threatened species or removing invasive species from ecosystems. Such drastic actions can shake up ecosystems substantially and sometimes the well-intended management creates unwanted and unexpected side-effects. It is therefore crucial that we know the potential for unwanted outcomes of such management actions.

We use a variety of mathematical and statistical techniques, combined with field data, to predict the type and likelihood of ecosystem-wide implications of translocations and eradications. The outcomes of this research help to prepare strategic monitoring plans that anticipate adverse outcomes conservation management, and trigger adaptive management actions to minimise the risk of such adverse outcomes.

We apply these novel approaches to a number of key case studies both enabling us to hone the approach and deliver support to mangers and stakeholders. Case studies include management of the Western Swamp Tortoises to new wetlands in Western Australia, the ecosystem loses and benefactors of the translocation of the ecosystem engineering Island Scrub Jay to long uninhabited islands in the Channel Islands off California’s Coast, and understanding potential changes from reintroducing a long lost carnivore into Indigenous lands within Booderee National Park.


Gloria Monsalve Bravo

Matthew Adams

Eve McDonald-Madden


Nigel Bean (Adelaide)

Kate O’Brien (UQ)

Nicki Mitchell (UWA)

Margaret Byrne (DPAW)

Parks Australia Christmas

Island Staff

David Lindenmayer (ANU)

Michael Bode (QUT)

Scott Sisson (UNSW)

Nick Dexter (Parks Australia)

Kevin Brown (Oregon State University)

Scott Morrison (TNC)

Scott Sillett (Smithsonian)

Kate Helmstedt (QUT)

Michael Bode (QUT)

Kerrie Mengersen (QUT)

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Western swamp tortoise (image: Bethany Nordstrom 


ARC Linkage grant

National Environmental Science Program (NESP)

ARC Centre for Excellence for Mathematical and Statistical Frontiers

Unintended consequences of cat eradication on Christmas Island 

Christmas Island is home to a suite of native animals found nowhere else, but also to invasive species including Asian wolf snakes, giant centipedes, feral cats and black rats. These invasive animals have contributed to many extinctions and declines of Christmas Island’s native species. The Australian Government is undertaking a range of conservation initiatives to safeguard the island’s native wildlife, including an island-wide cat eradication program. To maximise the outcomes of cat control, Parks Australia, who manage Christmas Island National Park, seek to anticipate and manage any unintended consequences.


Our research is assisting Parks Australia predict potential outcomes, particularly the potential for rat (Rattus rattus) numbers to increase following cat eradication, and whether this would impact nesting birds. Current and potential future rat impacts are uncertain for Christmas Island due to data deficiencies and because birds co-existed with (now extinct) native rodents as well as abundant land crabs – which may make them less vulnerable to rat impacts. To assess the effects of both cat and rat predation on red-tailed tropicbirds and other threatened Christmas Island species, Rosie is examining patterns of rat abundance and activity across the island, and relating this to forest bird abundance and nesting success, and to seabird nesting success. Rosie’s work is providing baseline data on the rat populations of Christmas Island and the impacts of rats on forest and seabirds, as well as developing methods for ongoing monitoring of rats during and after cat eradication.

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Interaction network for Christmas Island 


  • Rosalie Willacy

  • Eve McDonald Madden

  • Sarah Legge

  • Micha Plein


  • Samantha Flakus, Christmas Island National Park, Parks Australia

  • NESP Threatened Species Recovery Hub

  • Parks Australia, Christmas Island National Park

  • External advisors over the lifespan of the project: Dave Algar, Mark Holsworth, Sue Robinson, Janos Hennicke, Jon Woinarski


  • In-kind support from Parks Australia

  • Australia and Pacific Science Foundation

  • Birdlife Australia (Stuart Leslie Bird Research Award)

  • Australian Government – Department of Regional Development and Infrastructure

  • The Ecological Society of Australia - Holsworth Research Endowment

  • The Royal Society of Zoology, NSW (Ethel Mary Read Research Grant)

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Red tailed tropicbird, Christmas Island (image: M. Plein)

The value of model complexity for fisheries management

More than 99.8% of fisheries are assessed using single-species models. Since humans harvest multiple interacting species, not considering these interactions can lead to negative outcomes that reduce food security, eliminate human livelihoods, decrease economic production, and harm the environment. This project aims to quantify the benefits of using multi-species systems of ordinary differential equations for harvest decisions. Expected outcomes of the project include 1) guidance for fisheries scientists on when to use multi-species models for management, 2) improved decision making to reduce the risk of fishery collapse, 3) a new method for dynamic model validation in the face of limited data.



Matthew Holden

Anita Lin (Honours Student)

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Fish harvest (image: Bernard Spragg, Flikr, CCO 1.0)

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