Choices about land use and land management may provide a means of reducing atmospheric greenhouse gas levels.

This finding is from chapter 13 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: The author team benefited from a number of relevant technical input reports. One report described the findings of a three-day workshop held from November 29 to December 1, 2011 in Salt Lake City, in which a number of the chapter authors participated.94a7e73a-f733-42d4-be5a-5bd6d861a6e4 Findings of the workshop provided a review of current issues and topics as well as the availability and quality of relevant data. In addition, from December 2011 through June 2012 the author team held biweekly teleconferences. Key messages were identified during this period and discussed in two phases, associated with major chapter drafts. An early draft identified a number of issues and key messages. Based on discussions with National Climate Assessment (NCA) leadership and other chapter authors, the Land Use and Land Cover Change authors identified and reached consensus on a final set of four key messages and organized most of the chapter to directly address these messages. The authors selected key messages based on the consequences and likelihood of impacts, the implied vulnerability, and available evidence. Relevance to decision support, mitigation, and adaptation was also an important criterion for the selection of key messages for the cross-cutting and foundational topic of this chapter. The U.S. acquires, produces, and distributes substantial data that characterize the nation’s land cover and land use. Satellite observations, with near complete coverage over the landscape and consistency for estimating change and trends, are particularly valuable. Field inventories, especially of agriculture and forestry, provide very reliable data products that describe land cover as well as land-use change. Together, remote sensing and field inventory data, as well as related ecological and socioeconomic data, allow many conclusions about land-use and land-cover change with very high confidence.

Description of evidence base: The evidence base for this key message includes scientific studies on the carbon cycle at both global and local scales (summarized in Izzauralde et al. 2013; Hurteau 2013; and Cambardella and Hatfield 2013).91716084-2162-48ff-9ce4-872dd9b02168 a951fed3-9523-4679-8936-4487b3892e93 67d877c0-b3bd-41c2-b0f3-07deeaa5b1f5 The evidence base also includes policy studies on the costs and benefits and feasibilities of various actions to reduce carbon emissions from land-based activities and/or to increase carbon storage in the biosphere through land-based activities (summarized in Jones et al. 2013; and Pearson and Brown 2013).223881e2-78d1-45cc-8338-773ab23bcc76 96076018-91ed-45b2-8641-a91720962462 Foundational studies are summarized in the NCA Technical Input documents.74461848-086f-4ea7-b3b3-e1693e3a21d8 94a7e73a-f733-42d4-be5a-5bd6d861a6e4

New information and remaining uncertainties: A major study by the U.S. Geological Survey is estimating carbon stocks in vegetation and soils of the U.S., and this inventory will clarify the potential for capturing greenhouse gasses by land-use change (an early result is reported in Sohl et al. 2012b1eb2d34-4a06-4c83-a272-934338cbcda7). There is little uncertainty behind the premise that specific land uses affect the carbon cycle. There are, however, scientific uncertainties regarding the magnitudes of effects resulting from specific actions designed to leverage this linkage for mitigation. For example, uncertainties are introduced regarding the permanence of specific land-based stores of carbon, the incremental value of specific management or policy decisions to increase terrestrial carbon stocks beyond changes that would have occurred in the absence of management, and the possibility for decreases in carbon storage in another location that offset increases resulting from specific actions at a given location. Also, we do not yet know how natural processes might alter the amount of carbon storage expected to occur with management actions. There are further uncertainties regarding the political feasibilities and economic efficacy of policy options to use land-based activities to reduce the concentration of greenhouse gases in the atmosphere.

Assessment of confidence based on evidence: Given the evidence base and uncertainties, there is medium confidence that land use and land management choices can reduce the amount of greenhouse gases in the atmosphere.

References :

• Land Use and the Carbon Cycle: Advances in Integrated Science, Management and Policy (223881e2)
• Land Use and the Carbon Cycle: Advances in Integrated Science, Management and Policy (96076018)
• Land Use and Land Cover National Stakeholder Workshop Technical Report. Report prepared for 2013 National Climate Assessment (94a7e73a)
• Land Use and the Carbon Cycle: Advances in Integrated Science, Management and Policy (91716084)
• Land Use and the Carbon Cycle: Advances in Integrated Science, Management and Policy (a951fed3)
• Spatially explicit land-use and land-cover scenarios for the Great Plains of the United States (b1eb2d34)
• National Climate Assessment Technical Report on the Impacts of Climate and Land Use and Land Cover Change (74461848)
• Land Use and the Carbon Cycle: Advances in Integrated Science, Management and Policy (67d877c0)