Knowledge of forest biomass is necessary for reporting on the state of Canada’s forests. Biomass information is also required for ecosystem productivity and carbon budget models, and it serves as an indicator of the structural and functional attributes of forest ecosystems. Forest biomass information used in national reporting is mostly derived from regional and national estimates of forest biomass from Canada’s National Forest Inventory (NFI), and subsequent mapping of biomass using compiled NFI inventory data. Extending inventory data into maps of forest biomass, however, can be a challenging exercise that is influenced by a multitude of factors related to data availability and the scaling of tree-level allometric functions to the stand level. The spatial extent of existing forest inventories results in data gaps when regional or national biomass estimates are of interest, and this is a particular problem in the northern areas of Canada where access and resource requirements preclude the creation of large area inventories. As a result, there is a requirement to incorporate some level of remote sensing information from which biomass can be modeled and mapped. There are at least four different approaches that comprise recent, current and proposed biomass estimation and mapping activities in Canada. Earth observation data contribute to each of these approaches to varying degrees and while not all approaches result in large area biomass maps, they all provide a means of generating estimates for large regions. These four approaches for estimating and mapping biomass include: 1. Inventory Compilation, Estimation and Mapping: The historical approach involves a compilation of provincial forest inventories and was used to produce the first national forest biomass inventory in Canada. This approach has subsequently been replaced by the NFI, a plot-based system consisting of a 2 km by 2 km sample plot distributed 20 km apart in a systematic grid network across the country. Inventory data at NFI plots are now
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