The term 'ecosystem health' is widely used by scientists, land owners and managers, and policymakers at all levels to indicate a condition that is both aesthetically and economically acceptable. However, the expression has varying meaning for different interest groups, and the criteria by which it is assessed often vary from one ecosystem to another. Before health can be judged, for any ecoystem, it is necessary to identify indicators. We propose that certain ecosystem structural and functional characteristics may be used as measurements of health. Based upon assumptions that numerous stressors affect arid ecosystem, including climate, grazing, herbicide use and recreation, and that vegetation composition and cover is a response to ecosystem stress, it is hypothesized that satellite data may be used to evaluate ecosystem response through the use of a vegetation index such as the Normalized Difference Vegetation Index (NDVI). The research objective specific to the study reported here was to statistically evaluate the suitability of a suite of metrics derived from NDVI temporal profiles for discriminating variation in response to climate between mesquite and grassland systems.