Surface processes strongly the quality of the critical zone to sustain a tree cover. Conventionally, the availability of water and sufficient temperatures are considered to be the controlling factors for the presence of vegetation and the development of a , grass, shrub or forest cover. However, in environments with high rates of surface processes, such as deserts and high alpine regions, the lack of a stable regolith determines whether and which type of vegetation cover forms. Climate and environmental change will affect the interaction between surface processes, regolith and vegetation in the 21. Century and thus lead to the alteration of perennial vegetation cover. In environments with a strong influence of surface processes, the extent of trees and shrubs may develop in the opposite direction of the changes of conventional geo-ecologic indices. For example, in alpine environments enhanced mass wasting processes due to an increase of temperatures may lead to a decline in the tree line. Similarly, more runoff during extreme events can increase soil erosion in drylands, destroying the critical zone for plant growth. In this project, the current change of vegetation cover in selected borderline ecotones of the European Alps, the Canadian Rocky Mountains, the Negev Desert in Israel and the highlands of Tenerife are examined.