The Forest Observation System, building a global reference dataset for remote sensing of forest biomass

Forest biomass is an essential indicator for monitoring the Earth’s ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (aGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situdata for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situforest biomass database. aGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from feld measurements made in permanent research plots across the world’s forests. all plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS ofers the potential to improve the accuracy of RSbased biomass products while developing new synergies between the RS and ground-based ecosystem research communities.