Experts know more than just facts: eliciting functional understanding to help prioritise weed biological control targets

Prioritising investments in classical weed biological control (biocontrol) is a common decision-making challenge: biocontrol programmes can yield substantial benefits but are typically long-term and costly, and the outcome uncertain. Experts are often relied upon to help, but their role is generally restricted to providing facts and judgements to populate an existing prioritisation model, which in turn receives little scrutiny. We developed and applied a new prioritisation framework to guide biocontrol investment decisions by livestock industries that required eliciting experts’ functional understanding (including their in-depth knowledge of the theoretical and practical drivers of weed biocontrol programmes). This consultative and transparent framework drew on expertise from most biocontrol practitioners in Australia through a structured workshop, and the literature. Each of the 75 weed taxa considered was placed in a matrix according to their impact (current or potential) and the prospects of biocontrol achieving pre-defined management goals. There was considerable knowledge uncertainty regarding potential impacts, which is of concern when making pre-emptive investments. Feasibility (likelihood of finding host-specific agents) and likelihood of success (management goals being met, assuming that host-specific agents are available) of biocontrol were both assessed as low for 51 % of taxa. Predicted barriers to successful biocontrol were diverse and idiosyncratic, suggesting that application of more quantitative prioritisation approaches would be challenging. A short-list of 13 weed taxa was identified for further consideration as biocontrol targets, based on the trade-off between potential impact and prospects for biocontrol. Research priorities emerged from the prioritisation process that would maximise investment outcomes for each taxon. Only two short-listed taxa are new targets, reflecting the maturity of the biocontrol discipline targeting weeds of livestock industries in Australia. Accessing the in-depth functional understanding of experts resulted in explicit characterisation of the barriers to successful biocontrol and if/how they might be overcome, improved characterisation of uncertainty, and provided directed guidance for investment. Such an approach would be readily applicable to analogous decision-making challenges in other sectors and countries.