Modelling habitat suitability for multiple priority weed species to predict invasion hotspots for strategic management in complex landscapes

Abstract

Established invasive alien plant species require ongoing, costly management to reduce harm to agricultural and environmental values. Heterogeneous landscapes are often under threat from multiple long-established invasive plants, whose simultaneous management presents strategic and tactical challenges. Systematic monitoring of weed populations enables more strategic management by providing more detailed insights into invasion threats than the more readily available presence-only data. We leveraged six years of weed density monitoring and high-resolution environmental data to model habitat suitability for four high-priority weeds across the Australian Capital Territory. We developed habitat suitability maps for African lovegrass, Chilean needle grass, serrated tussock grass and St Johns wort. Maps were then standardised and combined to derive potential multi-species invasion hotspots at different management thresholds and explore patterns of secondary invasion threat. While some species shared environmental drivers such as elevation, each responded to distinct combinations and interactions among environmental drivers. Overall, we found approximately 71% of land had suitability for multiple weeds at various densities, but only 11% is suitable for two or more species to reach high densities. Areas suitable for most weeds often had St Johns wort as the next most suitable invader. These findings could improve management efficiency and reduce intervention challenges by focussing integrated control across species in a small number of priority areas. These findings support spatially explicit, multi-species decision-support tools for surveillance, prioritisation and strategic landscape-scale control.