WRASP: a spatial strategic weed risk analysis tool reveals important subnational variations in weed risks.
The number and diversity of introduced invasive plants, coupled with limited weed management budgets, require biosecurity managers to employ systems to prioritise weeds for management attention. To assist this process, an analytical protocol and spreadsheet tool were previously developed for post-border weed risk management (PBWRM). The popular PBWRM tool utilises a framework that ignores any spatial variation in risk factors within the geographical area of risk concern. However, invasive plants vary in risk factors such as invasiveness, potential impacts and feasibility of control as a function of spatially variable factors. Logically, the assessment of weed risks should also be spatially explicit, in order to best understand them and to target management appropriately. To address these concerns, we took the PBRWM logic and spatialised it, to allow weed managers to assess weed risks and management across geographical space. We illustrate this new spatial system using a case study of Senecio glastifolius in New Zealand, comparing the results of a spatial and an aspatial analysis of the risks it poses and the logical management options. The spatial view of risks revealed locations of higher and lower risk and suitability for management attention that were hidden by blanket, aspatial weed risk scores of the current PBWRM system. The national level risk was also significantly higher when considered in the light of the results from the spatial tool. The spatial tool, WRASP, takes its name from Weed Risk Assessment SPatial.