Mathaj M., Jeltsch F., Köchy, M. (2006)
Large parts of the Mediterranean that are too dry for conventional agriculture are used as rangeland for sheep and goats. Climate change effects on precipitation are likely to change the relative proportion of shrub and herbaceous cover, which will have consequences for the sustainable maximum stocking rate (SMS) in these areas. We used a spatially explicit model to simulate grazing and browsing by small livestock in five typical eastern Mediterranean valley landscapes ranging in humidity from arid (100 mm mean annual precipitation, MAP) to mesic (800 mm MAP). The landscapes comprise the three habitats wadi, north and south slope. Five climate change scenarios from -20% to +20% MAP were explored with the model.
Both shrub and herbaceous cover increased approximately logarithmically with MAP. Competition between shrubs and herbs, increasing with MAP, and facilitation of herbs, decreasing with increasing MAP, caused a more linear growth of herbs. In each landscape habitat (wadi, north slope, south slope) SMS increased linearly with relative change of MAP. The rate of increase rose with the humidity of the site. These strong linear relationships allow to suggest a simple algorithm for projecting SMS with only MAP as input parameter.