Detecting environmental change in eastern Australia: rangeland health in the semi-arid woodlands.

We examined changes in rangeland health in the semi-arid woodlands of eastern Australia at fixed sites between 1989 and 1999. Over the 11-year period there were significant declines in the quality of the vegetation, and changes in plant species were driven largely by seasonality, and to a lesser extent, amount of rainfall. Three indices of rangelands health (composition, function and stability) developed using site-based vegetation and landscape data, indicated that the majority of sites had intermediate values of the three indices, and few sites had either very low or very high values. The indices of composition and function were strongly correlated with the subjective ratings applied to each site at each measurement period. The results of this study highlight the difficulty of detecting change over extensive areas of rangeland, and of separating management-induced effects from climatic effects in an environment which experiences wide spatial and temporal variation in rainfall.