Humans have exploited forest biomass as a material and energy source for millennia, but population growth and increasing demand for resources have diminished the extent and condition of forests, with this impacting on the amount of carbon they store and exchange with the atmosphere. Increasingly, forests are being impacted by our changing climate. For this reason, the Global Climate Observing System (GCOS) considers above-ground biomass (AGB; expressed in tonnes per hectare) as an Essential Climate Variable (ECV). Information on forest biomass can also play a much wider role in understanding and predicting climate, for example in model initialisation and testing, estimating carbon turnover and inferring forest disturbance regimes, and through data assimilation in carbon cycle and climate models.
Objective
The primary science objective of ESA’s Climate Change Initiative (CCI) Biomass project is to provide global maps of above-ground biomass (Mg ha-1) annually for selected epochs (2007, 2010, 2015-2022) with these supporting quantification of biomass change.
Current mapping is at 100 m grid spacing with a target relative error of less than 20 per cent where AGB exceeds 50 Mg ha-1. Although this resolution is finer than required for current climate modelling, the information provided can be exploited by both climate and carbon cycle models as they develop.
About the project
The global maps of the above ground biomass of woody vegetation and changes over time have and continue to be generated from Synthetic Aperture Radar (SAR) data acquired at C-band by the European Space Agency's (ESA) Sentinel 1A & B and L-band by the Japan Aerospace Exploration Agency's (JAXA) Advanced Land Observing Satellites (ALOS PALSAR, ALOS-2 PALSAR-2). The retrieval algorithm is informed by information on forest height and cover density extracted from spaceborne LIDAR, including NASA's Global Ecosystem Dynamics Investigation Lidar (GEDI). The combination of these sensor types allows information on the amounts of foliage and woody plant material to be retrieved over time.
The mapping builds on algorithms developed initially through ESA's GlobBiomass Project, with these advanced through ESA CCI Biomass. The quality of the maps is assessed against existing and new ground and airborne data sets. The resulting global biomass data sets represent new information that can be used to support climate and carbon cycle modelling.