When Europeans first came to the U.S. as settlers, there were roughly a billion acres of ancient forests. America's trees have been under assault ever since. Westward expansion, industrialization, rapid population growth, the rise of the suburbs and various diseases have all exacted a toll. Today woodland acreage is down by about 25 percent - and much of it is populated with young trees. A new book tells the history of America through its trees. Like Dr. Seuss's environmental classic "The Lorax," it's a sad story, but one that's not without hope. In the next segment of our Environmental Outlook series - trees, forests and the making of a nation.