Carbon sequestration by the land absorbs an estimated 30 percent of fossil fuel carbon emissions, making it a critical part of the global carbon cycle; however, the exact amount and location of carbon stored in soils is not well quantified and can vary with local environmental conditions. Accurately assessing soil carbon storage is a management priority because these estimates are needed for updating land management plans and better understanding the global carbon cycle.
David D'Amore of the USDA Forest Service's Pacific Northwest Research Station and his colleagues used machine-learning to estimate the total carbon storage in the coastal temperate rainforest of the Pacific Northwest, the largest temperate rainforest in the world. They calculated a total of 4.5 gigatonnes, or 4.5 billion metric tons, of soil organic carbon within the first 1 meter of soil alone. That's approximately 2 percent of total soil organic carbon in North America. The researchers caution that even these improved soil carbon numbers may be an underestimate because carbon storage can extend far below 1 meter in depth. These estimates will be used by managers to meet legislated mandates for accurate carbon accounting and to update international databases of soil carbon maps that inform global carbon cycling models and climate forecasts.