This paper examines the permanence of agricultural land afforestation under stylized carbon markets at the regional level in the US. Attention is focused on Southern and Midwest regions which historically have experienced a relatively large amount of land-use change between the agriculture and forest sectors. The Forest and Agriculture Sector Optimization Model–Greenhouse Gases model is used to examine responses between sectors as part of the regional afforestation policy analysis. Main findings suggest that most of afforested area in the Midwest regions remains unharvested by mid-21th century but a significant percentage of afforested area in the Southern regions shifts back to agricultural uses by this time. We also simulated a policy where carbon sequestration credits paid for afforestation are reduced 40% relative to other mitigation actions. A permanence value reduction for afforestation further promotes the harvesting of afforested stands in the Southern regions. Also, it has an impact not only on grassland pasture but also on high productive cropland. Results of this analysis are robust to lower permanence value reduction rates for higher carbon prices and can serve as upper bound of impacts for lower carbon prices.