A multi-scale remote sensing approach to understanding vegetation dynamics in the Nama Karoo-Grassland ecotone of South Africa

Abstract

In this paper, we propose a methodology for upscaling fractional vegetation cover (FVC) estimates derived from unmanned aerial vehicles (UAVs) to a larger area using freely available Sentinel-1/2 and Landsat-8 satellite data in the semi-arid Nama-Karoo biome of South Africa. To the best of our knowledge, such an approach is still lacking yet critical for understanding human-environment interactions, degradation, and the impacts of climate change in this vulnerable dryland ecosystem. The proposed approach utilizes ultra-high spatial resolution UAV imagery (i.e. < 5 cm) to develop a high quality FVC product. The resulting product is then used to upscale and validate satellite-based estimates of FVC. The rationale for upscaling UAV estimates to the satellite-scale is not only to cover larger areas but also to exploit historical satellite times series data, in an attempt to understand past trends and vegetation dynamics in the Nama Karoo-Grassland ecotone. The proposed method is expected to produce the first-ever high-resolution continuous maps of FVC and its changes in the above-mentioned ecosystem. Such information is of vital importance as it could help decision makers to gain a better understanding of the extent at which mechanisms such as bush encroachment, grassland expansion, or degradation are occurring in dryland ecosystems.