Last reviewed on August 29, 2013

California Greenhouse Gas Inventory - Forests

Tree in a California forest
Growing trees remove CO2 from the air


The ARB’s forest sector greenhouse gas inventory tracks the removal of CO2 from the atmosphere by forests and rangelands and emissions of greenhouse gases to the atmosphere by processes occurring in the forests and the forest-products system in California. The forest sector inventory includes CO2 uptake and GHG emissions from wild and prescribed fires, the decomposition and combustion of residues from harvest and conversion/development, and wood products decomposition. The key greenhouse gases of concern are CO2, N2O, and CH4.

The exchange of CO2 between the atmosphere and the forests occurs through uptake by plant photosynthesis and release via plant respiration, decomposition, and combustion of organic matter. Nitrous oxide is emitted from combustion of organic matter and soil processes. Methane is emitted during incomplete combustion of organic matter and under anaerobic conditions in soils.

Forest sector emission and sequestration estimates in the ARB’s greenhouse gas inventory are based on a 2004 California Energy Commission study which quantified carbon stock in forests and rangelands. The study focused on a time period from 1994 to 2000 and was geographically limited to the northern part of the State. Results from the study were extrapolated to include the entire state and to other years. The wood products component of the forest sector inventory is based on ARB’s estimates of the amount of greenhouse gases generated and emitted from wood product decomposition in landfills and composting facilities in the state. Estimation methods are described in the ARB’s greenhouse gas inventory technical support document.

Planned Improvements

Improved estimates of CO2 uptake and greenhouse gas emissions by processes occurring on forest, range, and other land types, such as urban forests, are planned for future editions of the inventory. New research and analyses are required to better understand forest sector carbon accounting and the fundamental processes associated with sequestration and emissions. These efforts will be informed by consultation with experts in State and Federal land management agencies, academia, and other organizations.