Remote sensing applications for monitoring the spatial distribution of Bracken fern (Pteridium) in the Cathedral Peak: Drakensberg, South Africa

Bracken fern is one of the major invasive plants distributed all over the world currently threatening socio-economic and ecological systems due to its ability to swiftly colonize landscapes. The study aimed at reviewing the progress and challenges in detecting and mapping bracken fern weeds using multispectral remotely sensed data. Evidence from literature have revealed that traditional methods such as field surveys and modelling have been insufficient in detecting and mapping the spatial distribution of bracken fern at a regional scale. The applications of medium spatial resolution sensors have been constrained by their limited spatial, spectral and radiometric capabilities in detecting and mapping bracken fern. On the other hand, the availability of most of these data sets free of charge, large swath width and their high temporal resolution have significantly improved remote sensing of bracken fern. The use of commercial satellite data with high resolution have also demonstrated potential in providing fine spectral and spatial resolution capabilities that are essential in offering precise and reliable data on the spatial distribution of invasive species. However, the application of these data sets is largely restricted to smaller areas due to high acquisition costs. Studies on bracken fern classification have extensively adopted traditional classification methods such as supervised maximum likelihood classifier. Finally, since high spatial resolution sensors are expensive to acquire and have small swath width, the current study recommends that future research can also consider investigating the utility of the freely available recently launched new generation sensors such as Landsat 8 OLI with a global footprint which provides invaluable information for repeated measurement for bracken fern weeds over time and space.