For decades, mature forests have been treated as if their ability to store additional carbon gradually fades toward a biological ceiling. Once trees fill the available space and their canopies close, conventional satellite measurements often suggest that forest biomass changes very little. A new analysis, however, indicates that this apparent stability may be partly an illusion created by the way satellites observe forests. Across the conterminous United States, mature forests continue to accumulate carbon over large areas, but much of that growth is being missed by current satellite-derived biomass estimates. …The researchers compared several independent ways of detecting forest change, including satellite-derived biomass estimates, lidar observations, forest inventories and ecosystem models. …The contrast between the measurements was striking. Satellite estimates indicated that biomass in mature forests had undergone nearly neutral change over recent decades, implying little overall gain or loss. Forest inventories, by comparison, estimated that mature forests were accumulating about 102 teragrams of carbon each year.