It detects and tracks potential disturbances in forests across the conterminous U.S. by producing new national forest change products every eight days. Since 2010, ForWarn has detected environmental threats to forests caused by known and unexpected insects, diseases, wildfires, extreme weather, and other natural or man-made events.
ForWarn works by comparing a current daily vegetation “greenness” index with “normal” greenness that would be expected for healthy, undisturbed vegetation growing at a given
location, for a given time. Expected greenness is developed from the historical MODIS satellite image record.