The influence of reindeer pasturing on high mountain ecosystems in northern Norway was investigated using a landscape-ecological analysis. The most visible impacts of overgrazing are on the vegetation. In addition, soils and humus have been changed due to morphodynamic processes induced to a large extent by reindeer pasturing. Degradation of the high mountain landscapes within the last 30 years is described on 3 spatial levels: large-scale effects at specific localities, linear effects along reindeer fences, and small-scale effects on the altitudinal zonation of entire mountain systems. The structure of the ecosystem has changed completely due to reindeer pasturing, which has resulted in landscape degradation under great pasturing pressure. The processes that influence the ecosystem as a function of different pasture intensities are described and show a complex correlation and interaction between the ecofactors. These include destruction of vegetation cover, reduction of root density, erosion of humus and mineral soil horizons, reduction of soil moisture and soil stability, and changes in plant species composition. On the whole, degradation leads to a depression of the altitudinal belts, indicated by the new organization of the ecosystems. It can be concluded that reindeer herding at current levels is a destructive form of land use in the northern Norwegian high mountains and hence is not sustainable. The author believes that destruction of the natural environment could be reversed, although this is not to be expected.