Landscape Scale land degradation mapping in the semi-arid areas of the Save catchment, Zimbabwe

ABSTRACT

This research investigates the distribution and magnitude of vegetation loss in the Save catchment. The main objective is to map and quantify human-induced land degradation in the Save catchment, using Residual trend analysis (RESTREND) method. The investigation was done using Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI time series data, and gridded precipitation datasets from Climate Research Unit, recorded between 2000 and 2015. NDVI and rainfall time series, as well as ordinary least squares regression models used in the analysis, were computed in R statistical program. Geographic Information System (GIS) techniques were used in the quantification of degradation trends. The study revealed that approximately 18% of Save catchment experienced declining residual trends whilst increasing residual trends covered 34% of the area. These trends covered 1.7 Mha and 3.1 Mha, respectively. The study calculated the statistical significance of the declining trends. The results demonstrate that about 3.6 Mha experienced significant human-induced land degradation during the study period. This area represents 39% of the Save Catchment, 4%, 13%, and 22% of which were classified as severely, moderately, and lightly degraded, respectively. The results indicate the vulnerability of Save catchment to human-induced degradation. Severe degradation was noted in the central districts of the Save Catchment, notably Bikita, Chiredzi, and most parts of Chipinge. These findings demonstrate the effectiveness of RESTREND in removing influence of precipitation changes from land degradation. Based on these results, we recommend for the use of RESTREND method in detecting land degradation that is triggered by human actions.

KEYWORDS:

• Land degradation
• landscape scale
• NDVI
• trend analysis
• RESTREND

Disclosure statement

No potential conflict of interest was reported by the authors.