<b>Domke</b>, G., C. A. <b>Williams</b>, R. Birdsey, J. Coulston, A. Finzi, C. Gough, B. Haight, J. Hicke, M. Janowiak, B. de Jong, W. A. Kurz, M. Lucash, S. Ogle, M. Olguín-Álvarez, Y. Pan, M. Skutsch, C. Smyth, C. Swanston, P. Templer, D. Wear, and C. W. Woodall, 2018: Chapter 9: Forests. In Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report [Cavallaro, N., G. Shrestha, R. Birdsey, M. A. Mayes, R. G. Najjar, S. C. Reed, P. Romero-Lankao, and Z. Zhu (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 365-398, https://doi.org/10.7930/SOCCR2.2018.Ch9.
Atmospheric CO2 uptake in U.S. forests has partially offset carbon emissions in other sectors of the U.S. economy. The 2014 net uptake estimate from forestland remaining forestland was 742 Tg CO2e per year, which offset about 11% of gross U.S. GHG emissions. Assuming no policy intervention, the U.S. Department of Agriculture (USDA) reference scenario developed for the 2016 U.S. Biennial Report (USDA-OCE 2016) projects that annual carbon uptake will decrease to 320 Tg CO2e per year in 2050 as a result of forest aging, forest disturbance, and land-use change.
Government policies to boost forest carbon uptake have the potential to slow its projected decline. Available options include altering (e.g., slowing, intensifying, or redirecting) development and increasing afforestation of private land in the eastern United States (12 million ha) and reforestation of public land in the western United States (5 million ha) to achieve no net loss of forest area beginning in 2025. Relative to the reference scenario, this option is projected to increase cumulative carbon uptake by 26% from 2015 to 2060 (USDA-OCE 2016).
One way to estimate the societal impact of policy options to increase forest carbon uptake is to estimate the benefit in terms of avoided damages resulting from a net carbon emissions reduction. This benefit is estimated using social cost of carbon (SCC) estimates, which are dollar estimates of the long-term damage done by a ton of CO2 emissions in a given year. One report indicates that the SCC would increase from $42 in 2015 per 0.9 Mg CO2e emitted to $80 in 2050, which can be translated to equivalent savings for uptake of CO2e (using an average annual discount rate of 3%, with values in 2016 U.S. dollars; U.S. Interagency Working Group on Social Cost of Carbon 2013). As an example of the potential benefit of exploring policy options to boost forest carbon uptake, the current value of increased forest carbon uptake under a policy that reduces land development and increases afforestation and reforestation relative to the reference scenario is $132 billion (Bluffstone et al., 2017).
A policy option that involves afforestation of private forestland to increase forest carbon uptake could be achieved with incentives to private landowners. The USDA has five voluntary incentive programs, which account for more than 95% of USDA conservation spending (USDA-ERS 2014). When estimating benefits of incentive programs to increase forest carbon uptake, problems of “additionality” and “leakage” may lead to overestimating carbon uptake gains (Lubowski et al., 2006). Estimates of forest carbon uptake by voluntary incentives may not be fully additional because some of this carbon would have been taken up on private forestland without the program. Furthermore, leakage could occur if landowners clear forestland for farming to compensate for land enrolled in the incentive program. Both additionality and leakage need to be accounted for when estimating the benefits of incentive programs to increase carbon uptake on private forestlands.
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