Forest Carbon: Estimates of 2010 forest carbon stock and components (aboveground, coarse woody debris, and soil/other) are from Williams et al. (2021b) following methods described for the Southeast US in Gu et al. (2019). To estimate carbon stock, attributes were determined for all forested 30-m pixels in the continental United States. A forest carbon cycle model trained to match Forest Inventory and Analysis (FIA) data was used to predict carbon stocks for 2010 based on site‐level attributes of forest type group, years since disturbance, and site productivity class. Results were iterated backward in time to provide continuous, annual reporting of forest carbon dynamics for each pixel. Most prior studies lacked spatial detail on the age of forest stands that persisted in a forested condition during the satellite data era, but this study used remotely sensed biomass to estimate the stand age condition of these persisting, intact forests, distinguishing relatively young stands (e.g., 30 to 50 years old) from older stands.

Williams, C. A., N. Hasler, H. Gu, and Y. Zhou. 2021b. Forest Carbon Stocks and Fluxes from the NFCMS, Conterminous USA, 1990-2010. ORNL Distributed Active Archive Center

Gu, H., Williams, C. A., Hasler, N., & Zhou, Y. (2019). The carbon balance of the southeastern U.S. forest sector as driven by recent disturbance trends. Journal of Geophysical Research: Biogeosciences, 124, 2786– 2803. https://doi.org/10.1029/2018JG004841

Future Forest Carbon Stock & Potential Sequestration: The method used to calculate the 2050 carbon stocks was the same as described above, except that the model assumed no disturbances to the forests after year 2010. Because the modeled forests grow undisturbed from 2010 onward, the results can be used to estimate the potential carbon sequestration if the forest were free of harvest, fire, or conversion. While conservation efforts can limit harvest and conversion, it is difficult to predict future disturbances and users should be aware that the actual sequestration may be less than predicted. The Total Potential Sequestration is estimated as: (2050 stock - 2010 stock). The analysis tool also calculates the Average Annual Sequestration Rate per selected site ((2050 stock - 2010 stock)/40 years) and per acre ((2050 stock-2010 stock)/40 years/acres). The potential sequestration layer in the map is displayed as metric tons / acres. The values in the carbon summary report for a polygon are reported in both metric tons and metric tons/acre/year.

Reforestation: This tool is not designed to identify places with the highest potential for reforestation to increase carbon sequestration. To address that question, check out www.ReforestationHub.org

Soil Carbon: Estimates of soil organic carbon (SOC) for 0-30 cm topsoil layer at 250-m resolution for the conterminous USA (CONUS) are from Oak Ridge Lab (Guevara et al. 2020). The estimates are for the period 1991-2010 and were derived using the USDA Rapid Carbon Assessment (RaCA), which used over 6000 field soil samples and multiple environmental variables representative of the soil-forming environment coupled with a machine learning approach (i.e., simulated annealing) and regression tree ensemble modeling for optimized SOC prediction. Across the continental US, nearly 31% of SOC was found in forests, 28% in croplands, and 35% in grasslands and shrublands respectively.

Guevara, M., C.E. Arroyo-cruz, N. Brunsell, C.O. Cruz-gaistardo, G.M. Domke, J. Equihua, J. Etchevers, D.J. Hayes, T. Hengl, A. Ibelles, K. Johnson, B. de Jong, Z. Libohova, R. Llamas, L. Nave, J.L. Ornelas, F. Paz, R. Ressl, A. Schwartz, S. Wills, and R. Vargas. 2020. Soil Organic Carbon Estimates for 30-cm Depth, Mexico and Conterminous USA, 1991-2011. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1737

Current Land Cover Adjustments: For both the Forest Carbon and Soil Carbon datasets, we used the 2019 National Land Cover Database (NLCD) to remove forest and soil carbon pixels that occurred on open water, developed land (high, medium, and low intensity), and barren land associated with solar and mining footprints.

Total Carbon: Estimates for total carbon in the carbon calculator use Forest Carbon 2010 for all cells with forest cover and Soil Carbon 2010 for all cells with non-forest cover. To combine the two datasets, we resampled the SOC data to a 30-m resolution to align with our other data products. Please note that resampling to a higher 30-m resolution introduces false accuracy as the original SOC data was at a lower 250-m resolution.