This chapter discusses tourism’s impacts on global environmental change. Tourism affects four key Earth-system processes under threat: biodiversity loss, freshwater availability, land-use change, and climate change. On a global scale, tourism impacts on climate change are most significant. However, on a local or regional scale, tourism can be a considerable driver of change in the other processes, sometimes to an extent of global proportions. The various components of tourism act differently in these processes. Tourism mobility as a whole is generally the most problematic. The causes of tourism impacts are explored per system process and mitigation priorities are addressed. Mitigation of impacts is essential, also for the sustainable development of tourism. Strategy development needs an integrated approach, as measures to solve one issue can be counterproductive for other processes and goals.