In the Peruvian highlands, climate change and inadequate management are causing land degradation and collapse of the pastoral system. Our research project was aimed at assessing the impact of grazing on dry Puna ecosystem, as understanding and predicting vegetation changes in harsh environments in the face of different disturbance regimes is required for aware and effective management. The study area was the Salinas and Aguada Blanca National Reserve. Two experimental areas were selected, characterized by deep soils with gentle slopes and by shallow soils with steeper slopes.

Using an analysis of aerial photographs from 1942, 1985 and 2004 we assessed the impact of changing land tenure and land-use regimes on the cover of thicket vegetation on the Grahamstown commonage. Land-use impacts were examined by comparing plant species composition within three vegetation types between sites incorporated into commonage for different lengths of time and sites outside the commonage. Results showed that thicket cover increased by 87% between 1942 and 1985 but declined by 11% between 1985 and 2004.

Mountain ecosystems are, however, fragile and particularly vulnerable to the adverse impacts of climate change, deforestation and forest degradation, land-use change, land degradation and natural disasters.