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Radar backscatter is sensitive to vegetation fresh biomass7. At long wavelengths (0.7 m or longer), radar penetrates deep into the canopy and the backscatter energy depends on a combination of variables including the size, number density, and the water content and wood specific gravity of branches and stems. However, radar backscatter suffers from gradual loss of sensitivity as biomass increases. The phenomenon referred to as ‘saturation’occurs often in radar backscatter at shorter wavelengths, but is not unique to radar and forests, and can occur in all types of remote-sensing measurements, even for non-woody vegetation. However, at longer wavelengths (> 0.7 m), radar backscatter remains sensitive to a wide range of AGB. Variation in tree density may impact radar backscatter, but does not cause loss of sensitivity. In spatially heterogeneous forests, the largest source of error in deriving the relationship …