Ecosystem invasion by non-native species represents one of the biggest threats to biodiversity. Non-native species management on offshore islands is especially challenging and resource demanding for conservation. Non-native plants increase the extinction risk of native plants and animal populations. Identifying ways of improving the cost-effectiveness of managing them is therefore critical for positive conservation outcomes.
In a recent paper, led by Nathalie Butt and Amelia Wenger, we used a novel Bayesian Belief Network (BBN) model to investigate non-native plant dispersal on the approximately 550 islands along the Pilbara coast, Western Australia. Ten vertebrate species that are listed as threatened by both the IUCN and EPBC rely on island habitats in the region, including marine turtles and marsupials. We found that, annually, around 9,000 weed propagules of 16 species are arriving on these offshore islands via wind, currents, flooding, and human dispersal. We uncovered eight species on five islands that arrived only via human dispersal and could therefore be amenable to eradication and subsequent quarantine and education programs. We also identified 23 islands where at least two weed species had a greater than 50% chance of establishment, making these islands candidates for control programs. Analysing these data to identify priority species and locations for targeted management would have been infeasible with previous methods. However, with our innovative BBN we were able to establish which species and which islands were key targets for management.
Our evidence-based, tractable approach to non-native species management allows us to determine where and how to act, by indicating which actions (quarantine, surveillance, control, eradication) will be most effective in each location. Just as important, we can tell managers where management would not be cost-effective. The BBN software is generically applicable to any archipelago, and to any non-parasitic non-native species of flora or fauna, and is thus a valuable tool in invasive species management planning.