Understanding the spatial distribution of eroded areas in the former rural homelands of South Africa: Comparative evidence from two new non-commercial multispectral sensors

Abstract

In this study, we determine the most suitable multispectral sensor that can accurately detect and map eroded areas from other land cover types in Sekhukhune rural district, Limpopo Province, South Africa. Specifically, the study tested the ability of multi-date (wet and dry season) Landsat 8 OLI and Sentinel-2 MSI images in detecting and mapping eroded areas. The implementation was done, using a robust non-parametric classification ensemble: Discriminant Analysis (DA). Three sets of analysis were applied (Analysis 1: Spectral bands as independent dataset; Analysis 2: Spectral vegetation indices as independent and Analysis 3: Combined spectral bands and spectral vegetation indices). Overall classification accuracies ranging between 80% to 81.90% for MSI and 75.71%-80.95% for OLI were derived for the wet and dry season, respectively. The integration of spectral bands and spectral vegetation indices showed that Sentinel-2 (OA = 83, 81%), slightly performed better than Landsat 8, with 82, 86%. The use of bands and vegetation indices as independent dataset resulted in slightly weaker results for both sensors. Sentinel-2 MSI bands located in the NIR (0.785-0.900 μm), red edge (0.698-0.785 μm) and SWIR (1.565-2.280 μm) regions were selected as the most optimal for discriminating degraded soils from other land cover types. However, for Landsat 8OLI, only the SWIR (1.560-2.300 μm), NIR (0.845-0.885 μm) region were selected as the best regions. Of the eighteen spectral vegetation indices computed, NDVI and SAVI and SAVI and Global Environmental Monitoring Index (GEMI) were ranked selected as the most suitable for detecting and mapping soil erosion. Additionally, SRTM DEM derived information illustrates that for both sensors eroded areas occur on sites that are 600 m and 900 m of altitude with similar trends observed in both dry and wet season maps. Findings of this work emphasize the importance of free and readily available new generation sensors in continuous landscape-scale soil erosion monitoring. Besides, such information can help to identify hotspots and potentially vulnerable areas, as well as aid in developing possible control and mitigation measures.

Local community involvement in nature conservation under the auspices of Community‐Based Natural Resource Management: A state of the art review

“…Nonetheless, the challenge with Landsat is that it has a medium spatial resolution of 30 m, which makes it difficult to be applied on a smaller scale (Pape, 2006). This is, however, now compensated by the new 10 m Sentinel 2 multispectral instrument at a 5‐day interval and a global footprint (Sepuru & Dube, 2018; Thamaga & Dube, 2018a, 2018b).…”

Modelling seasonal variation of gully erosion at the catchment scale

“…The Sentinel‐2 mission, launched on 23 June 2015, comprises a land monitoring constellation of two satellites (Sentinel‐2A and Sentinel‐2B) providing global optical imagery at a 5‐day interval (revisit time), using a multi‐spectral instrument (MSI) (Sepuru & Dube, 2018). The Sentinel‐2 MSI has 13 reflective wavelength (ranging from 433 to 2190 nm) spectral bands; four 10 m visible and near‐infrared bands; six 20 m red edge, near‐infrared, and shortwave infrared bands; and three 60 m bands (Drusch et al, 2012).…”

Assessment of homegarden agroforestry for sustainable land management intervention in a degraded landscape in South Africa

“…More than 20% of cultivated lands have decreasing productivity due to degradation, with 13% of the global degrading area being in Africa south of the Equator (UNEP, 2012). Land degradation is one of South Africa's most significant environmental problems (Sepuru & Dube, 2018), especially in agricultural areas; with 70% of South Africa's agricultural land classified as degraded (DEAT, 2006). The Greater Sekhukhune District Municipality in the Limpopo Province of South Africa (where this study was conducted) is one of the areas experiencing severe land degradation (DEAT, 2006; DWS, 2019).…”

“…being in Africa south of the Equator (UNEP, 2012). Land degradation is one of South Africa's most significant environmental problems (Sepuru & Dube, 2018), especially in agricultural areas; with 70% of South Africa's agricultural land classified as degraded (DEAT, 2006).…”