California Natural & Working Lands Inventory

View looking up at tall trees from below

CARB's Natural and Working Lands (NWL) Inventory is a quantitative estimate of the existing state of ecosystem carbon stored in the State's land base. It provides estimates of carbon stocks and stock change, and - in the case of wetlands - greenhouse gas (GHG) flux in California's landscape, and attributes stock changes to disturbances. The NWL inventory is an important tool for informing how California's land base contributes to the State's climate goals and tracking statewide progress toward the State's long-term objectives for NWL.

The NWL Inventory tracks how much carbon exists in California's ecosystems and where that carbon is located at discrete moments in time, and estimates how much carbon is moving in and out of the various land types and carbon pools. It consists of forest and other natural lands, croplands, urban forests, wetlands, and soil carbon. CARB developed the NWL Inventory using design principles established by the Intergovernmental Panel on Climate Change (IPCC). CARB's NWL inventory methodologies utilize a combination of remote sensing data and ground-based measurement data, as well as other default assumptions where California-specific data are not available. The first edition of the NWL Inventory that includes all land types is now available in the section below.

2018 Edition of the NWL Inventory

The NWL inventory summary report provides background information on the legislative directives and the history of NWL Inventory development at CARB, presents the fundamentals of the inventory accounting framework, and summarizes the current understanding of ecosystem carbon stocks and trends in stock change in California. The technical support document describes the detailed methods, data, assumptions, and parameters used in the development of the NWL Inventory.

Separate from the CARB NWL Inventory, the California Board of Forestry (BOF) and the California Board of Forestry and Fire Protection (CAL FIRE) maintain an inventory of carbon in California’s forests. CARB and the BOF launched their respective forest carbon inventory efforts in different years in response to different legislative mandates. CARB began developing new inventory methodology in 2009 and completed an inventory report in response to the 2016 legislation Senate Bill 859. The BOF inventory was initiated after the 2010 legislation Assembly Bill 1504, calling for the BOF to ensure a certain level of forest carbon sequestration in California’s forests. Due to differences in objectives and legislative mandates, the two inventories cover different land types and time periods and use different methodologies. The different approaches complement each other and help identify ways to further refine future estimation. Staff in the two agencies collaborated to prepare a detailed inventory comparison and an FAQ summarizing the inventories’ differences and similarities. The two agencies’ staff will continually work together to further refine the two inventories.

Previous Inventory Documentation

Forest & Other Natural Lands Inventory

The forest and other natural lands inventory includes carbon uptake by vegetation, carbon losses associated with wild and prescribed fires, the decomposition and combustion of residues from harvest, and conversion to other land types. Previous inventory estimates for this category were based on a 2004 California Energy Commission study which quantified carbon stocks and change in forests and rangelands in the northern part of the State from 1994 to 2000. Results from the study were extrapolated to include the entire state and to other years, and the estimation approach afforded few options for updating. In 2015, researchers from UC Berkeley developed a data-driven methodology for assessing carbon stocks and changes for all land categories in California except agricultural and urban areas. The methods use California specific land-based data sets and satellite remote sensing data.

The covered ecosystems include forests, woodlands, shrub lands, grasslands, wetlands and other natural lands. The method includes carbon contained in live and dead vegetation pools. Data sources for the method include ground-based data from the Forest Inventory and Analysis (FIA) program of the USDA-Forest Service, remote sensing products from NASA's MODIS sensor, geospatial vegetation attributes and disturbance activity (fire, harvest etc.) data from the federal Landscape Fire and Resource Management Planning Tools Project (Landfire.gov), and ancillary data on shrublands and grasslands. The method enables analysts to retrospectively assess ecosystem carbon stocks and to attribute stock-changes to fire and other processes. Results of a recent analysis for a period spanning 2001 to 2010 are presented here.

Inventory tables for forest and other natural lands during the 2001-2010 period:

Change in Land Carbon Stocks and Stock-change Attribution, 2001-2010

Technical Support Document, companion to the inventory for the 2001-2010 period:

Technical Support Document for California's 2001-2010 Forest and Other Natural Lands Carbon and Emission Inventory

Development of the new methodology reports

Public Workshop & Presentations

October 23, 2018 Public Workshop

CARB staff hosted a public workshop to discuss a draft NWL Inventory on October 23, 2018. Workshop materials are provided below.

Workshop Slides

November 7, 2016 AB 32 Scoping Plan Workshop

The presentation at the November 7, 2016 AB 32 Scoping Plan Workshop provides an overview of the IPCC inventory framework, inventory methodology (for all land types, including cropland and urban forest), and summary of inventory results:

Natural & Working Lands Inventory Presentation