This chapter will inventory the reasons why mountains are important to humankind, before reviewing how mountain environments have evolved in the past, prior to the more recent decades where direct anthropogenic activities have been accelerating change. The chapter will then review some of the natural and human drivers of environmental change before summarizing, in the fourth part, the possible or plausible changes that many mountain domains are likely to face in the future, because of the multiple stress factors imposed by human activities. Finally, the chapter will close with a brief review of cross-cutting issues and possible adaptation and mitigation strategies.