Hi Jose: Not sure what you mean by "url based data" that can prove anything, but there are a lot of studies and historical records that illustrate this statement. Because the statement is limited to western Oregon, you can look at the much-documented forestation histories of the Willamette, Umpqua, and Rogue River valleys as beginning points. Historical maps, Osborne and aerial photos, survey records, and eyewitness accounts buttress later scientific studies on this topic.