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The arid zone is characterised by episodic rainfall events which produce infrequent vegetation growth pulses (Pickup, 1989). This vegetation then senesces and decays, or is consumed by herbivores. The magnitude and composition of the vegetation pulse is controlled by position in the landscape (soil fertility, additional run -on) and is also affected by grazing history. However, the effect of past grazing is often very difficult to determine in spatially complex landscapes receiving seasonally variable rainfall. Ground -based monitoring systems are now well established in most states. Methods used generally recognize the importance of quantitative data and multivariate analysis techniques. However, the problem remains that point -based assessments are labour intensive and widely spaced. They often have difficulty in separating human- induced change from background natural processes (Pickup, 1989). A satellite -based approach to land assessment utilises the advantages of repetitive and complete data coverage for areas of interest. Procedures are now available for the rapid processing of digital data to provide an index of vegetation cover (Pickup et al. 1992). The results of spatial and temporal analyses that have allowed grazing impact to be determined from Landsat MSS data over large areas are described in this poster. source:Introduction