Old-growth is defined as trees older than 200-years-old while forest degradation is defined as forest transformation or loss due to timber harvest, land development, urban expansion or fire. Old-growth data is derived from the Forest Service's 2012 Northwest Forest Plan and excludes all forest degradation data. Wildfire data consists of available records dating between the year 1835 and the end of the 2020 fire season. Forest degradation data is derived from various publicly available Geographic Information System data sets that contain records dating between the year 1900 and 2020. Data for many significant early and mid 20th century events, such as the Tillamook Burn and urban development, is unavailable and excluded from these maps.
Data compiled from: "NWFP LSOG 20 year Monitoring Old Growth Structure Index GT 200 year Old" raster map (Davis / USDA / USFS / PNWRS), "Global Forest Change 2000 - 2019" (Hansen / UMD / Google / USGS / NASA), "BLM OR Harvest Treatments" (Bureau of Land Management, Oregon State Office), "Activity Timber Harvest" (U.S. Forest Service), "Inter-agency Fire Perimeter History All Years" (USFS / BLM / BIA / FWS / NPS / AIFC / CalFire), "Current wildfire perimeters" (CalFire) and "US Historical Fire Perimeters WFL1" (GeoMAC).