Zhengxi Tan, Shuguang Liu, Terry L. Sohl, Yiping Wu, and Claudia J. Young

Environmental Science

Significance

There has been a critical knowledge gap for national biological C sequestration potential assessment due to a lack of relevant information about federal lands that cover nearly 30% of the whole US territory. Here, we present the results from a multimodel simulation approach and fill the current knowledge gap by revealing the C sequestration potential of federal lands across the conterminous United States and their contribution to the national ecosystem C budget through 2050. This kind of information can be a fundamental reference for federal agencies to develop long-term strategies for mitigating greenhouse gas (GHG) emissions and sustaining federal land resources.

Abstract

Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands’ contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency’s land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal.

See http://www.pnas.org/content/112/41/12723.abstract.html?etoc

PNAS October 13 2015;  vol. 112 no. 41 12723–12728

Fig. 1. Spatial distribution of the baseline ecosystem carbon stock (in vegetation and the top 20-cm depth of soil, averaged from three GCMs and three models) in federal lands across the CONUS and its changes from 2006 to 2050 under three scenarios, A1B, A2, and B1.