Potential of GIS and remote sensing in mapping land degradation: catchment of the Manyame River, Zimbabwe

The Manyame River Catchment area in Zimbabwe is experiencing severe land degradation mainly due to legal and illegal land husbandry practices. These practices are negatively impacting the sustainability of the existing ecosystems. The conditions of the land can be inferred using its vegetative cover, e.g., the Normalised Difference Vegetation Index (NDVI). Quantitative data relating to land degradation based on notable physical features such as gullies, for the Manyame River Catchment at landscape scales are poor. This study focused on the distribution and magnitude of land degradation in the Manyame River Catchment area. The study mapped out the contours of human-induced land degradation using a residual trend analysis (RESTREND) method. In particular, the study used remotely sensed data (NDVI and precipitation time series) to analyse the shifts over the period 2000–2017. The analysis used R statistical software packages (RESTREND and Kendall) and Geographic Information System (GIS) techniques to quantify the degradation trends. The results indicated extracts of those areas which experienced significant human-induced land degradation during the study period. RESTREND effectiveness was assessed using Mann–Kendall. The results of this study can be used by natural resource practitioners in monitoring, assessing, and managing environmental changes using GIS tools.