| Summary: | Thesis (MSc (Geography and Environmental Studies))--University of Stellenbosch, 2005. === Land degradation in Lesotho is undermining the finite resource on which people
depend for survival. Use of satellite imagery has been recommended for monitoring
land degradation because remotely sensed data enable monitoring of large areas at
more frequent intervals than intensive ground based research. Various techniques
have been developed for land cover change detection. In the present study, vegetation
changes were identified by image differencing, which involved finding the difference
between the earlier date NDVI image and the later date image. NDVI images are
among products that are generated from the NOAA AVHRR sensor to provide
information about the quantity of biomass on the earth’s surface. The resulting NDVI
change data showed land areas that had experienced vegetation loss, which were
identified as potentially degraded. The change data were combined with other data
sets to determine how potentially degraded areas were influenced by different
environmental variables and population pressure. These data sets included land cover,
ecological zones, elevation, soil and human and livestock populations. By integrating
NDVI data with ancillary data, land degradation was attributed to both demographic
pressure and biophysical factors. Widespread degradation was detected on the arable
parts of the Lowlands where cultivation was intensive and human settlements were
extensive. Signs of grassland depletion and forest decline were also evident and were
attributed to population expansion, overgrazing and indiscriminate cutting of trees and
shrubs for firewood. Extensive biomass decline was also associated more with soils in
the lowlands derived from sedimentary rocks than soils of basalt origin that occur
mostly in the highlands. Significant degradation was evident on gentle slopes where
land uses such as cultivation and expansion of settlements were identified as the main
causes of the degradation. There was evidence of greater vegetation depletion on
north and east-facing slopes than on other slopes. The depletion was attributed to the
fragility of ecosystems resulting from intense solar radiation. The study demonstrated
that NOAA AVHRR NDVI images could be used effectively for detecting land cover
changes in Lesotho. However, future research could focus on obtaining and using
high resolution data for detailed analysis of factors driving land degradation.
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