Refining estimates of U.S. reforestation opportunities for climate mitigation: updated algorithms and analyses

Reforestation has substantial potential for carbon sequestration in the conterminous United States. My inspection of the results of a recent novel study of potential reforestation in the US revealed potentially important issues in some locations related to harvested forests and productive cropland. Here, I describe a study that refined the methods to address these issues and included an assessment of the albedo impact of reforestation. One update to improve identifying forest harvest caused substantial decreases in sequestration potential. In addition, five different approaches were developed for updating the estimate of marginal cropland, allowing for variability in the definition of “marginal”. Sequestration potential increased or decreased, depending on approach. Because these updates were somewhat offsetting, the summed sequestration potential for the US was about 86% of the original results. At state and finer scales, substantial increases and decreases occurred. Geographic patterns were similar to the original study, with highest potential in the eastern US and coastal western US. These areas of high sequestration would be less affected by the modified albedo following reforestation than other areas. The refinements described here likely result in greater accuracy and higher confidence in some locations and situations of potential reforestation actions in the US.