2015 RPA Update: Forest Carbon Projections for the United States David Wear John Coulston USDA Forest Service, Research and Development Southern Research Station RPA/FIA

The RPA Assessment The Forest and Rangeland Renewable Resources Planning Act of 1974 mandates a national report (RPA Assessment) on the conditions and trends of renewable resources on all forest and rangelands every ten years. The RPA Assessment provides a snapshot of current U.S. forest and rangeland conditions and trends; identifies drivers of change; and projects 50 years into the future (2010-2060 for the Update). Provides authoritative outlook for America’s forests and rangelands.

Resources Evaluated Land Resources Forest Resources Urban Forests The RPA Assessment includes analyses of the following resources, as well as the potential effects of climate change: Land Resources Forest Resources Urban Forests Forest Products Forest Carbon Rangeland Resources Water Resources Wildlife, Fish, and Biodiversity Outdoor Recreation

Evolution of Projections From 2010 RPA Assessment to USDA Integrated Projections and 2015 RPA update New forest carbon inventory system Full consistency between inventory and projection Supported by FIA continuous/annual forest inventory Revised land use projections Accounting for recession/coordination within USDA Land development deferred Decomposition (attribution) of changes Land use, disturbance, …

Land based carbon change Other rural land (crops, range,…) Developed land Forest land CFF COD COO COF CDD CFO CFD Inventories had lumped land use transfers and sequestration (Cff) Separating these elements is essential for evaluating how to increase forest C Goal: isolate Cff

Forest Carbon 1990-2015 Net forest sequestration ranged from 112 to 133 Tg per year between 1990 and 2015 and averaged 122 Tg per year. Forest area increase accounted for about 41 percent of the total forest carbon stock change.

C dynamics (South) High degree of detail is included in the change dynamics. The new FIA inventory system allows for this enhanced monitoring, projections, and policy analysis.

Forest Carbon 1990-2015 Forests in the eastern United States account for over 60 percent of U.S. forest carbon stocks and 80 percent of net forest carbon sequestration.

Projection methods Simulate transition of all forest inventory plots South; North; Great Plains Rockies; Pacific Northwest; Alaska Simulate transition of all forest inventory plots Based on empirical evidence from measured inventory transitions Forest aging Land use change Timber harvests Fire Other disturbances Simulate transition of forest inventory aggregates Based on empirical evidence from split panels or single set of measured plots Forest aging Land use change Timber harvests Fire Other disturbances A regionally specific modeling approach accounts for differences in aging and disturbance dynamics. Projections of forest carbon link biological forest dynamics with socioeconomic dynamics, affecting land use and timber harvesting.

Projections: Land use assumptions Projections were driven by socioeconomic scenarios designed by a USDA team for coordinated analysis of economic activity affecting all lands. For the Reference scenario, observed forest area was assumed to continue growing for the next decade, level off, and then begin to fall after 2030. Area of forest land use from the U.S. National Greenhouse Gas Inventory, and projections for three scenarios, 2014-2060.

Developed land

Projected US forest carbon (three scenarios) Cff plus land use transfers Land use transfer Cff Forests are projected to remain an important sink of atmospheric carbon throughout the projection period. The total forest carbon inventory increases at historical rates between 2015 and 2025 and then at a decreasing rate that approaches zero by 2060 due to land use transfers. After accounting for land use transfers, the amount of forest sequestration of atmospheric carbon declines very gradually during the projection period. Sequestration changes gradually; transfers rapidly Gradual decline in sequestration from atmosphere

Projections: Regional forest carbon Western regions lose more sequestration than East East shifts to about 90% of sequestration by 2040 Rockies go quickly to zero / C source by 2025

Forest area by ownership and age

Harvest Wood Products Inventory Projections Projections are sensitive to: Population change Income change Associated changes in housing starts Carbon stored in durable wood products and solid waste disposal are tracked separately Relationship between cutting and production Relationship between production and product Additions HWP Pool

Projections: Harvested wood products carbon The amount of wood products carbon declined to historic lows during the recent economic downturn. Wood products carbon storage rates have recovered and are expected to increase to historic averages in future decades. Recovery and future depends strongly on recovery of housing demand.

Projections: Total forest sector Forest Sequestration plus land use transfers Forest sequestration plus wood products C Forest sequestration Total forest sector carbon sequestration—the sum of forest sequestration and changes in HWP carbon storage—increases from 2005 to 2020 and then declines very gradually. Estimates of (1) changes in forest carbon stocks, (2) net forest carbon sequestration, and (3) forest sector sequestration of carbon measured in Tg carbon/year for the Reference scenario, 2005-2060.

Key questions: Land Use

Key question: Land Use Population growth and land development projected to continue Slowed during recession; returning with recovery Agriculture--forest dynamic Led to strong net gain in forests since 1980 Gains have dampened since 2000 Projections: from stable to net losses of forests in next decade

Implications U.S. forests continue to sequester significant amounts of atmospheric carbon Isolating carbon sequestration requires accounting of transfers among land uses and to harvested wood products. Rates of carbon sequestration vary strongly across regions: eastern regions account for 80 percent of historical sequestration and as much as 90 percent of projected sequestration. Projections indicate an increase then gradual slowing of sequestration over time: sequestration under a reference scenario peaks in 2020 at 159 Tg/year and then declines to 122 Tg/year in 2060.

Conclusions Protecting the sink strength and the stock requires first maintaining land base Intensive monitoring is indicated Potential rapid change in position due to land use Uncertainty regarding climate effects Percent contribution of harvested wood products increases in future Strong links to market activities

Ongoing work / Remaining ?’s Steady enhancement of methods Growing FIA data library improves forecasts and projections Especially important for the West where measurement frequency is lower Enhancing the land use projections FIA-RPA Especially in the East where land use dynamics are most substantial Climate change effects RPA Shifting types / productivity / land uses Harvested wood products carbon models FIA-TPO-RPA Enhancing links to products markets analysis

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