This paper compares transient carbon fluxes to and from forests during climatic change in a pure natural model of ecosystem adjustment and also in a model that captures the human response to these changes. Both models incorporate forest dieback and regeneration, forest redistribution, and changes in ecosystem production during climatic change. The natural model predicts that forested ecosystems in the United States will release 2.5 to 6.3 Pg carbon during the next 7 decades under climatic change. The model including human response shows that markets will mitigate, and even reverse, these fluxes by managing some forests for timber and storing carbon in wood products.