Partially The range of historic variation has not been determined. Annual data are available for the area affected by the European gypsy moth, southern pine beetle, mountain pine beetle, spruce budworm, and western spruce budworm. Similar county of incidence data are available for various diseases, including dogwood antracnose, beech bark disease and butternut canker. Areas of infection overlap for many of these pests with the result that percent of forest affected is not meaningful. There are no good data on area affected by competition from exotic species.
Annual data are available for area burned by wildfire.
Storms such as hurricane Hugo affect large areas of forest land, but the range of historic variation has not been established to determine if Hugo was especially significant. The total area of forest land has stabilized in the United States. While some forest land is being cleared, some is being added through natural reversion of cropland and afforestation. No data were found for forest area subject to permanent flooding, salinization, and domestic animals and they are not believed to be significant issues in the United States. Missing Data Forest health is a major issue in the United States.