On the accuracy of conservation managers' beliefs and if they learn from evidence-based knowledge: a preliminary...

Despite the significant impetus placed on the need for conservation managers to base their decisions on evidence-based findings, few studies have compared the accuracy of "evidence" versus experience-based knowledge. Furthermore we are not aware of any study that has tested the willingness of managers to change their beliefs after being exposed to evidence-based findings. Here, we tested nine managers' beliefs before-and-after being shown findings from an evidence-based study. The questions centered on the effectiveness of 'Working for Water' (WfW) in reducing invasive alien plant cover in two large catchment projects over a seven year period, as well as the managers' forecasts of WfW's effectiveness of reducing invasive alien plant cover, and the factors that underpin its effectiveness. We also assessed the financial cost of implementing the evidence-based assessment. We found that in comparison to the evidence-based findings, the managers underestimated the ineffectiveness of operations in reducing invasive alien plant cover in the one catchment and overestimated the ineffectiveness of the other catchment. All the managers whose estimates differed from the evidence-based findings were willing to change their beliefs. Surprisingly, however, when it came to forecasting WfW's effectiveness in the catchments, all the managers, with the exception of one project manager, were unwilling to reduce their optimistic estimates of the time required to control invasive alien plants from the two catchments. With regard to the drivers of effectiveness, the managers ranked their performance as the most important criterion whereas the data model emphasized variables related to site suitability for alien plant growth. Finally, we showed that it would only cost between 0.33% and 1.67% of the two projects' annual budgets to assess all sites, depending on the frequency of the monitoring. This preliminary investigation highlights how evidence-based findings alone, even if presented and explained to managers, might not result in managers learning and updating their beliefs.