The Unintended Climate Consequences of Carbon Sequestration in North American Forests

Abstract

Planting forests is one of few readily available and proven approaches to mitigating climate change through the sequestering of atmospheric carbon dioxide (CO2). In order to avoid a doubling in the concentration of atmospheric CO2 from preindustrial values by mid-century will require a multitude of technologies and approaches - carbon sequestration through forest planting being one of the more practical ones. However there is considerable uncertainty over whether afforestation/reforestation will actually do more harm than good. Planting a forest may decrease the surface reflectivity resulting in greater net radiation being absorbed at the surface and thus, surface warming. In some cases this warming can more than offset the climate benefit derived from carbon sequestration. Using a dynamic global vegetation model, the competing effects of fraction cover of forest, stand age, and local climate on the total benefit to the climate system is evaluated. Model results indicate that regionally there are large variations in the climate benefit of forest placement. This study offers new insight on the feasibility of large-scale forest planting as a climate mitigation strategy.