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, including the amount of carbon they store and exchange with the atmosphere.
The Global Climate Observing System considers above-ground biomass (AGB) an Essential Climate Variable due to its functions as both a source of atmospheric CO2 (and other greenhouse gases) when forest is lost under Land Use Change or by degradation, and as a sink for CO2 due to forest growth.
Information on forest biomass can also play a much wider role in understanding and predicting climate, for example in model initialisation, model testing, estimation of carbon turnover, inferring the forest disturbance regime, and data assimilation in carbon cycle and climate models.
The primary science objective of ESA’s Climate Change Initiative (CCI) Biomass project was to provide global maps of above-ground biomass (Mg ha-1) for three epochs (2010, 2017 and 2018), with these being capable of supporting quantification of biomass change. For Phase 2 of the project annual mapping will continue creating a time series from 2015/16 - 2022, plus a 2005/7 epoch.
The 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, it will allow more refined information to be inferred (e.g. forest age structure and the disturbance regime) that is relevant for climate and has the potential to be exploited by carbon cycle and climate models as they develop.
About the project
To generate maps of biomass and biomass change, maximum use will be made of spatial data from past, current and future Earth observation missions. The products rely on ESA's C-band (Sentinel 1A & B) and JAXA's L-band Synthetic Aperture Radar (ALOS-2 PALSAR-2) with additional information from space borne LIDAR (e.g. NASA's Global Ecosystem Dynamics Investigation Lidar GEDI). The combination of these sensor types will allow information on the amounts of foliage and woody plant material and their distribution to be retrieved, both spatially and vertically, and over time.
The mapping will be achieved using algorithms developed within a globally consistent biomass retrieval framework and builds on the experience gained during ESA’s GlobBiomass Project. The quality of the maps will be extensively verified through the use of existing and new ground and airborne data sets. The resulting global biomass data sets will provide the carbon cycle and climate science community with the capacity to integrate global biomass layers into their models.
The major technical objective is to build on pre-existing methods for estimating biomass from satellite data (notably those developed during the GlobBiomass project), identify the weaknesses in these methods (arising from algorithmic, sensor or data issues) and address these issues using methodological advances that are applicable globally and consider different biomes. The project will also make significant advances in understanding how biomass data are used in carbon cycle and climate modelling, for example in model initialisation, model testing, carbon turnover time modelling and data assimilation.