Reforestation Much of North America, especially in the eastern U.S. and Canada, was deforested early in the 19th century.  Much of this forest is now regrowing.  As the forest grows in size, carbon is incorporated into the trees. This  accounts for perhaps 0.5 gigatons of carbon.  Of the 7.5 gigatons being put into the atmosphere, we’ve now accounted for roughly 5.5. That leaves 2 to go.