The session will present the state of the art of observational, experimental and modelling approaches used to study the impacts of global change drivers (climate, land use, atmospheric N deposition, elevated CO2 and biotic invasions) on alpine ecosystems. The session brings together workers on long-term projects from many parts of the world (North and South America, Asia and Europe). Long-term experimental manipulation and observation-based studies focusing on ecosystem structure and function will be presented first, followed by ecosystem level integration of trace gas flux observations; modelling studies will lead up to a panel discussion and synthesis (one or two talk-slot length). The session will begin with presentations of two long-term experimental warming experiments in alpine tundra: the first will introduce an IR warming experiment on Niwot Ridge, and the second report on work carried out on experimental warming and grazing by using open-top chambers on the Tibetan Plateau. Then the role of land use in the shaping of structure and functioning of Himalayan Kobresia sedge heaths will be discussed, followed by a talk on long-term impacts of grazing management on alpine pastures in the Pyrenees. An overview of the impacts of N deposition on the Niwot Ridge tundra structure and functioning will be followed by a talk about the Swiss alpine free-air CO2 enrichment experiment. An overview of observed alien species in alpine ecosystems worldwide will close the first part. In the scond part, speakers will discuss the ecosystem level integration of CO2 and H2O exchanges observed on Niwot Ridge, and below-ground organisms and processes along and their importance in the light of global change drivers. Finally, a talk about modelling approaches applied to alpine ecosystems will close the organised part of the session. Two additional slots are left free for the conference organisers to add additional talks, or allow a moderated panel discussion and synthesis.