Human Impacts and Ecosystem Resilience in the Southern Andes

The shrubby vegetation of the Andean slopes of Central Chile is being subjected to a variety of perturbations caused by human activities. Some perturbations are absorbed; others significantly change the existing vegetation patterns. This paper describes and discusses the results of experiments designed to evaluate the impacts caused by the introduction of rabbits and goats, and by the increasing incidence of fire. The analysis demonstrates that type and degree of impact depends upon the type of stimulus, the relationship to other perturbations, the amount of vegetation cover, and the past history of the area under study. These characteristics are discussed in the context of ecosystem stability and instability.