Wessels, Konrad JPrince, SDFrost, PEVan Zyl, D2007-02-062007-06-072007-02-062007-06-072004-05-15Wessels, KJ, et al. 2004. Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1 km AVHRR NDVI time-series. Remote Sensing of Environment, vol 91(1), pp 47-670034-4257http://hdl.handle.net/10204/1563http://hdl.handle.net/10204/1563There is a pressing need for an objective, repeatable, systematic and spatially explicit measure of land degradation. In northeastern South Africa, there are large areas of the former homelands that are widely regarded as degraded. A time-series of seasonally integrated I km, Advanced Very High Resolution Radiometer (AVHRR) normalized difference vegetation index (NDVI) data was used to compare degraded rangelands [mapped by the National Land Cover (NLC) using Landsat Thematic Mapper (TM) imagery] to nondegraded rangelands within the same land capability units (LCUs). Nondegraded and degraded areas in the same LCU (paired areas) were compared by: testing for differences in spatial mean SigmaNDVI values, calculating the relative degradation impact (RDI) as the difference between the spatial mean SigmaNDVI values of paired areas expressed as a percentage of nondegraded mean value, investigating the relationship between RDI and rainfall and comparing the resilience and stability of paired areas in response to natural variations in rainfall. The SigmaNDVI of degraded areas was significantly lower for most of the LCUs. Relative degradation impacts (RDI) across all LCUs ranged from 1% to 20% with an average of 9%. Although SigmaNDVI was related to rainfall, RDI was not. Degraded areas were no less stable or resilient than nondegraded. However, the productivity of degraded areas, that is the forage production per unit rainfall, was consistently lower than nondegraded areas, even within years of above normal rainfall. The results indicate that there has not been a catastrophic reduction in ecosystem function within degraded areas. Instead, degradation impacts were reflected as reductions in productivity that varied along a continuum from slight to severe, depending on the specific LCU3309306 bytesapplication/pdfenCopyright: 2004 Elsevier Science IncAVHRRAdvanced very high resolution radiometerNDVINormalized difference vegetation indexLCULand capacity unitsSigmaNDVIHuman-induced land degradationRangelands - South AfricaEnvironmental sciencesArticleWessels, K. J., Prince, S., Frost, P., & Van Zyl, D. (2004). Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1 km AVHRR NDVI time-series. http://hdl.handle.net/10204/1563Wessels, Konrad J, SD Prince, PE Frost, and D Van Zyl "Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1 km AVHRR NDVI time-series." (2004) http://hdl.handle.net/10204/1563Wessels KJ, Prince S, Frost P, Van Zyl D. Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1 km AVHRR NDVI time-series. 2004; http://hdl.handle.net/10204/1563.TY - Article AU - Wessels, Konrad J AU - Prince, SD AU - Frost, PE AU - Van Zyl, D AB - There is a pressing need for an objective, repeatable, systematic and spatially explicit measure of land degradation. In northeastern South Africa, there are large areas of the former homelands that are widely regarded as degraded. A time-series of seasonally integrated I km, Advanced Very High Resolution Radiometer (AVHRR) normalized difference vegetation index (NDVI) data was used to compare degraded rangelands [mapped by the National Land Cover (NLC) using Landsat Thematic Mapper (TM) imagery] to nondegraded rangelands within the same land capability units (LCUs). Nondegraded and degraded areas in the same LCU (paired areas) were compared by: testing for differences in spatial mean SigmaNDVI values, calculating the relative degradation impact (RDI) as the difference between the spatial mean SigmaNDVI values of paired areas expressed as a percentage of nondegraded mean value, investigating the relationship between RDI and rainfall and comparing the resilience and stability of paired areas in response to natural variations in rainfall. The SigmaNDVI of degraded areas was significantly lower for most of the LCUs. Relative degradation impacts (RDI) across all LCUs ranged from 1% to 20% with an average of 9%. Although SigmaNDVI was related to rainfall, RDI was not. Degraded areas were no less stable or resilient than nondegraded. However, the productivity of degraded areas, that is the forage production per unit rainfall, was consistently lower than nondegraded areas, even within years of above normal rainfall. The results indicate that there has not been a catastrophic reduction in ecosystem function within degraded areas. Instead, degradation impacts were reflected as reductions in productivity that varied along a continuum from slight to severe, depending on the specific LCU DA - 2004-05-15 DB - ResearchSpace DP - CSIR KW - AVHRR KW - Advanced very high resolution radiometer KW - NDVI KW - Normalized difference vegetation index KW - LCU KW - Land capacity units KW - SigmaNDVI KW - Human-induced land degradation KW - Rangelands - South Africa KW - Environmental sciences LK - https://researchspace.csir.co.za PY - 2004 SM - 0034-4257 T1 - Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1 km AVHRR NDVI time-series TI - Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1 km AVHRR NDVI time-series UR - http://hdl.handle.net/10204/1563 ER -