Remote Sensing of Invasive Australian Acacia Species: State of the Art and Future Perspectives

Remote sensing is a rapidly advancing technology with a wide range of applications in ecosystem management. This chapter presents a literature review focusing on ecological applications of remote sensing in the context of invasions of Australian Acacia species (‘wattles’) at the global level. Of ten studied species worldwide, only half, namely A. cyclops, A. dealbata, A. longifolia, A. mearnsii and A. saligna, were studied more than once. Research hotspots are South Africa and Portugal, while large gaps exist elsewhere. The most common study objective is mapping the distribution of invasive wattles using machine learning. Novel approaches using deep learning and citizen science are still largely untapped resources, and comparative approaches to test the transferability of these novel techniques are rare. Coastal dunes and forests are frequently studied, while agroforestry systems, for example, are neglected despite a high interest in using wattles in these habitats. Beyond mapping, remote sensing is used for impact assessments, for example to map effects on nitrogen cycling and water balance, and suggestions have been made on how to include environmental heterogeneity in impact models. However, research in this field is scarce, and further studies as well as conceptual work are required. Other applications include monitoring of invasion after (bio)control, analysing the importance of land use/land cover in the invasion process and modelling invasion dynamics. Phenological information has high potential for mapping wattles, but this possibility needs to be explored further, particularly in combination with environmental impact assessments. The global nature of wattle invasions and recent technological advancements in remote sensing analyses enable both local-scale studies as well as worldwide comparisons to assess context dependency from both a (technical) remote sensing angle and an ecological perspective. We envision that the increased popularity of remote sensing studies on invasive wattles can be projected into the future to fill these research gaps and to inspire remote sensing-based monitoring systems as the backbone of invasion management.