By Map by Robert Simmon, based on data from Woods Hole Research Center. (http://visibleearth.nasa.gov/view.php?id=76697) [Public domain], via Wikimedia Commons

Map of the United States above-ground woody biomass with 66 ecoregions delineated. It shows the tons of trees and their forests by hectare. Based on the map and palette created by NASA’s Earth Observatory employee Robert Simmon. Credit – Robert Simmon NASA/Wikimedia Commons (Public domain)