- Abstract Comprehensive information on the spectral reflectivity of several desert habitats and of dominant desert vegetation are presented. No previous high resolution spectral reflectance measurements were made in this semi-arid Sahara-Arabian phytogeographic zone. Due to the relative homogeneity of the region, in terms of terrain type and comprehensive sampling, the local scale surface albedo was estimated to be about 30–33 per cent. It was also possible to revisit the currently accepted hypothesis on the observed contrasts in surface reflectivity between protected and overgrazed areas. It seems that anthropogenic activities, which prevent the accumulation of crust or destroy an existing crust, rather than the overgrazing mechanism itself, are the main reasons for the sharp contrast between the protected and overgrazed surfaces.