Most analyses to date of options for mitigating the risk of global climate change have focused on reducing emissions of carbon dioxide and other greenhouse gases (GHGs). Much less attention has been given to the potential for storing (or “sequestering”) significant amounts of carbon in forests and other ecosystems as an alternative means of offsetting the effect of future emissions on GHG concentrations in the atmosphere. The tendency to overlook sequestration opportunities can lead to incorrect and overly pessimistic conclusions about both the cost and feasibility of addressing global climate change in the decades ahead.
To remedy that gap, and to inform U.S. policymaking, the Pew Center asked economists Robert Stavins of Harvard University and Kenneth Richards of Indiana University to synthesize and expand upon available studies of forest-based carbon sequestration in the United States. They analyze the true opportunity costs of using land for sequestration, in contrast with other productive uses, and examine the multiple factors that drive the economics of storing carbon in forests over long periods of time. These factors include forest management practices for different tree species and geographical regions; the costs of land and competing prices for agricultural products; the ultimate disposition of forest materials, including the potential for fire damage as well as harvesting for use in different kinds of end products; the specific carbon management policy employed; and the effect of key analytical parameters, including in particular the discount rate applied to future costs and benefits. The authors then adjust the findings from major recent studies of forest sequestration to reflect consistent assumptions in each of these areas and use the normalized results to establish a likely range for the overall scope and likely costs of large-scale carbon sequestration in the United States.
Their conclusions are striking. Estimated costs for sequestering up to 500 million tons of carbon per year—an amount that would offset up to one-third of current annual U.S. carbon emissions—range from $30 to $90 per ton. On a per-ton basis, these costs are comparable to those estimated for other climate change mitigation options such as fuel switching or energy efficiency. A sequestration program on this scale would involve large expanses of land and significant upfront investment; as such, it would almost certainly require a phased approach over a number of years and careful attention to policy details to ensure efficient implementation. Nevertheless, the results of this study indicate that sequestration can play an important role in future mitigation efforts and must be included in comprehensive assessments of policy responses to the problem of global climate change.
The Pew Center and the authors are grateful to Ralph Alig, Ronald Sands, and Brent Sohngen for helpful comments on previous drafts of this report. A future Pew Center domestic policy report will focus on design aspects of a domestic mitigation program that includes sequestration. Insights from this report and from companion papers in the Pew Center’s Economics series are being utilized to develop a state-of-the-art assessment of the costs to the United States of taking action to address climate change.