Every summer for approximately the past seventy years, an insect and disease aerial detection survey has been flown of all the forested acres of Washington state (except where noted in the digital data by large 'NF' (not flown) areas). This survey is a cooperative effort between the U.S. Forest Service and the WADNR with two different flight observers each sketching a two mile swath out their side of the plane. The primary mission of the survey is to record recently killed and defoliated groups of trees throughout the state, and to continually build a historical record of these trends. The vast majority of damage found is caused by insect and disease damage agents; however, trees killed by early spring feeding of black bears or by events such as winter storms, fires, floods and landslides are recorded as well. Current defoliation can be detected as soon as the affected foliage changes color that year. However, whole tree mortality is not current since only flagged trees (i.e., trees which have a bright red, orange, or yellow foliage color) are recorded. This means that trees killed the year of the survey will not have changed color yet and so a one year lag time results. Since only this distinctive color or "signature" of the tree can be seen. It is an educated guess as to the causal agent. We therefore use ground surveys to reinforce our estimates as much as possible. Example: When bear damage is spotted while surveying, a polygon is drawn on the map of the size and location of the damage. The polygon is then labeled with the appropriate damage agent (i.e. Bear) and the number of trees affected rounded to the nearest five. No vertical data is recorded.
