Reconstructing lost ecosystems: A risk analysis framework for planning multispecies reintroductions under severe uncertainty

Katie A. Peterson, National Socio-Environmental Synthesis Center (SESYNC), Annapolis, MD, Megan Barnes, Saul Cowen, Leslie Gibson and Colleen Sims, Western Australia Department of Biodiversity Conservation and Attractions, Perth, Australia, Cailan Jeynes-Smith, Queensland University of Technology, Brisbane, Australia, Christopher M. Baker, School of Mathematics and Statistics, The University of Melbourne, Australia, Michael Bode, School of Mathematical Sciences, Queensland University of Technology, Brisbane, Australia

Background/Question/Methods
Reintroductions are an important tool in threatened species conservation. Increasingly, reintroduction projects are becoming more complex, often involving the translocation of multiple species. Ecological theory predicts that the sequence and timing of reintroductions will play an important role in their success or failure. Risk analyses are needed to compare and understand the potential consequences of different reintroduction strategies, and these analyses must incorporate the complexity and uncertainty of ecosystem dynamics. Here, we use ensembles of ecosystem models to compare 23 alternative reintroduction strategies on Dirk Hartog Island, in Western Australia. Following the removal of sheep, goats and feral cats, the Western Australian government is reintroducing 13 native fauna species to restore the globally important natural and cultural values of this island.
Results/Conclusions
Ensemble modelling predicts that almost all of the species (~12.5 out of 13, on average) will successfully establish in the ecosystem, regardless of which reintroduction strategy is undertaken. The project can therefore proceed with greater confidence and flexibility regarding the reintroduction strategy. However, the identity of the at-risk species varies between strategies, and depends on the structure of the species interaction network, which is quite uncertain. The model ensembles also offer insights into why some species fail to establish, predicting that most unsuccessful reintroductions will be the result of competitive interactions with extant species. An ensemble modelling approach also creates a foundation for formal adaptive management as the reintroduction process continues.