Human concerns about the effects of climate change on forests are related to the values that forests provide to human populations, that is, to the effects on ecosystem services derived from forests. Service values include the consumption of timber products, the regulation of climate and water quality, and aesthetic and spiritual values. Effects of climate change on ecological systems are expected to change service flows, people's perception of value, and their decisions regarding land and resource uses. Thus, social systems will adapt to climate changes, producing secondary and tertiary effects on the condition of forests throughout the world. This chapter explores how social systems might interact with changing climate conditions in determining the future of forested ecosystems in the United States.