High-resolution mapping of introduced buffel grass (Cenchrus ciliaris) in central Australia

Buffel grass (Cenchrus ciliaris) is an introduced pastoral grass that threatens arid ecosystems worldwide. Its ability to rapidly colonise new areas, outcompete native plants, invade a diversity of habitats and fuel fires make it a disaster for native biodiversity, infrastructure and remote communities. This species was implicated in the fires that devastated Lahaina, Hawai'i in 2023, and in Australia, it is one of the most significant environmental threats to semi-arid rangelands. The management of buffel grass requires detailed knowledge of its current spatial distribution, information currently lacking for most of inland Australia. We modelled and mapped buffel grass occurrence at two sites in central Australia by applying singular value decomposition to a time series of vegetation indices derived from Sentinel-2 satellite imagery. In both study areas, buffel grass could be modelled/mapped with high accuracy (≥ 85%) at the native resolution of the satellite imagery (10 m). Our study areas were much larger (up to 2800 km²) than previous attempts to map buffel grass in both Australia and overseas, and our model accuracies were either comparable or higher than previous efforts. The buffel grass maps can aid resource managers and practitioners in their control and monitoring efforts, and our method uses free, open-source software, making it more cost effective than methods using drones and/or aerial surveys.