Mapping Global Boreal Forest Biomass Density

Space-based laser altimetry has revolutionized our capacity to characterize terrestrial ecosystems through the direct observation of vegetation structure and the terrain beneath it. Advanced information about the structure, distribution, and biomass of global forests provide critical ecological insights and opportunities for sustainable forest management and enhancing forest conservation and ecosystem services. However, the uncertainty of biomass estimates in forests, particularly boreal forests, are largely due to their increasing heterogeneity over the landscape as well as impacts of edaphic, environmental, and disturbance conditions. Data from NASA’s ICESat-2 mission provide the first comprehensive look at canopy structure for boreal forests from space-based lidar as it is the only space-based laser altimeter capable of mapping vegetation in northern latitudes. Baseline aboveground biomass maps provide modeling groups with important constraints on climate and carbon cycle models, and enable the long-term monitoring of changes to aboveground biomass stocks in the future from deforestation and degradation.

The first objective of this research was to create ICESat-2 aboveground biomass density (AGBD) models for the global entirety of boreal forests at a 30 m spatial resolution and apply those models to ICESat-2 data from the 2019–2021 period. Here, ICESat-2 data were resampled to 30 m along-track resolution to estimate biomass. These ICESat-2 biomass estimates were then fused with Harmonized Landsat Sentinel (HLS) data to create a wall-to-wall data biomass product. Remote sensing observations at a fine scale (~30 m – 1 ha) provide a means to estimate aboveground biomass and capture changes as a function of land use, disturbance, and growth.

The next phase of research will explore annual changes in boreal biomass as a function of disturbance (logging or fire). As ICESat-2 continues to collect data, vegetation change mapping becomes possible. In the boreal, forest growth is slow, and increases in height may require a decade or more of coverage. Forest disturbance, however, results in large losses in AGB, and the time series of ICESat-2 is theoretically capable of quantifying the carbon emissions associated with this change.

For more information, you can find the following manuscripts:

• Duncanson et al., “Forest Aboveground Biomass Estimation with GEDI and ICESat-2 in Boreal Forests,” 2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS, Brussels, Belgium, 2021, pp. 670-672, doi: 10.1109/IGARSS47720.2021.9553209
• Neuenschwander et al. “Towards Global Spaceborne Lidar Biomass: Developing and Applying Boreal Forest Biomass Models for ICESat-2 Laser Altimetry Data.  https://dx.doi.org/10.2139/ssrn.4792013
• Neuenschwander et al. “Validation of ICESat-2 Terrain and Canopy Heights in Boreal Forests” https://doi.org/10.1016/j.rse.2020.112110
• Feng et al. “A systematic evaluation of multiresolution ICESat-2 ATL08 terrain and canopy heights in boreal forests”  https://doi.org/10.1016/j.rse.2023.113570