Because of its generally low density of humans and few settlements, the circumpolar boreal forest is often viewed as an untouched wilderness. However, archeological evidence indicates that humans have inhabited the region since the continental glaciers disappeared 8,000–12,000 years ago. This paper discusses the ecological impacts that humans have had on the boreal forest ecosystem through their activities in prehistoric, historic, and recent times and argues that the boreal forest has always been a cultural landscape with a gradient of impacts both spatially and temporally. These activities include hunting, trapping, herding, agriculture, forestry, hydroelectric dam projects, oil and natural gas development, and mining. In prehistoric times, human impacts would generally have been more temporary and spatially localized. However, the megafaunal extinctions coincident with arrival of humans were very significant ecological impacts. In historic times, the spread of Europeans and their exploitation of the boreal's natural resources as well as agricultural expansion has altered the composition and continuity of the boreal forest ecosystem in North America, Fennoscandia, and Asia. Particularly over the last century, these impacts have increased significantly (e.g., some hydroelectric dams and tar sands developments that have altered and destroyed vast areas of the boreal forest). Although the atmospheric changes and resulting climatic changes due to human activities are causing the most significant changes to the high-latitude boreal forest ecosystem, any discussion of these impacts are beyond the limits of this paper and therefore are not included.