Remote Sensing of Surface Properties. The Key to Land Degradation and Desertification Assessments

Since the International Convention on Desertification of the United Nations has come into force, the need to measure degradation processes in these areas has further increased. While standard methods for undertaking such measurements are imperfect or expensive, remote sensing with air- or space-borne sensor systems offers considerable potential. It provides a comprehensive spatial coverage, is intrinsically synoptic, collects objective, repetitive data and is thus ideally suited for monitoring environmentally sensitive areas. However, the relatively low spatial resolution provided by remote sensing satellites implies that one needs to exploit the spectral contrast between soil and vegetation and their intermediate states to develop surrogate measurements of degradation. Relationships between climate and environmental conditions, which may be of primary importance at a global scale, become problematic when local factors such as topography, lithology and soil properties determine the redistribution of water available for plant growth. Suitable remote sensing approaches must therefore concentrate on both, vegetation and soil-related assessments of ecosystems.