Use of expert knowledge to elicit population trends for the koala (Phascolarctos cinereus)
Adams-Hosking, C, McBride, MF, Baxter, G, Burgman, M, de Villiers, D, Kavanagh, R, Lawler, I, Lunney, D, Melzer, A, Menkhorst, P, Molsher, R, Moore, BD, Phalen, D, Rhodes, JR, Todd, C, Whisson, D & McAlpine, CA 2016, Diversity and Distributions, pp. 1-14.
Regional populations of koalas are continuing to change across Australia with evidence showing rapid declines, stable and growing populations. Despite the importance of understanding population trends for this threatened species, there are diverse opinions held by experts regarding koala abundance and, hence, the status of koala populations. Expert elicitation was used here as a method to derive estimates of koala populations and trends from a number of koala experts.
The data collected from the elicitation process was used to synthesise expert knowledge regarding koala populations into a reliable representation of the current state of knowledge. A total of 15 koala researchers underwent a structured four-step elicitation process which required participants to individually answer questions, discuss anonymously displayed answers to these questions in a face-to-face workshop, and subsequently revise initial estimates to questions. The results were aggregated to indicate a population of approximately 329,000 koalas in Australia based on estimates of mean population sizes for each bioregion and state, and an average of 24% decline over the past three generations. The percentage loss in Queensland, New South Wales, Victoria and South Australia over the past 15-21 years was calculated at 53%, 26%, 14% and 3% respectively. Uncertainties for mean population size in selected bioregions were also recorded. The authors agreed that aggregation may not be suitable where uncertainties or opposite opinions exist; rather, analysis of these results separately would be more suitable gain an insight into the reason behind these differences.
This valuable tool for data extraction and amalgamation proved that a broad agreement of results could be achieved to estimate the mean population size of koalas, as well as quantify level of uncertainty for each bioregion and state. The process of asking questions, discussing answers, then asking questions once more meant that it was not necessary for experts to show a high level of certainty before making informed estimates.
Studies utilising empirical data generally form the basis of koala literature; however, the benefit of expert elicitation shown in this study was that such a large amount of information from experts could be combined to provide an overview of koala population abundances and trends. This is crucial for updating management plans for koalas and inform actions for the protection of this species.
Summarised by Robyn Boldy
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