Drought and insect-induced forest mortality in the western United States, 1999 - 2023

This dataset encodes drought and insect-induced forest mortality in US Forest Service regions 3, 4, 5, and 6. These data were rasterized at 4 km resolution from polygons in the US Forest Service Insect and Disease Survey. Damage polygons were filtered to only include mortality observations where the damage-causing agent was either drought, bark beetles, or wood borers. Each pixel is mortality severity, or the proportion of treed area affected by mortality. Surveyed pixels with no mortality observations were assigned a value of zero, and pixels with tree cover less than 10% were masked. I followed the methods in Andrus et al. (2025) to harmonize different severity measurements over time. Other covariates are: elev: Pixel elevation according to ASTER global DEM. slope, northness, eastness: Terrain metrics derived from elev. fire: Proportion of pixel area where fires burned according to MTBS. prcp: Water-year precipitation according to Daymet (from October of the prior year through October of the year coordinate). vp: Mean JJA vapor pressure according to Daymet. tmin: DJF minimum air temperature according to Daymet (including December of the prior year). mortality: Forest mortality severity as describe above. treecover: Percent forest cover in pixel according to the 2021 NLCD treecover product, resampled to 4 km resolution. abies, pinus, populus, pseudotsuga, tsuga: Basal area for the given tree species according to USFS Individual Tree Parameter Maps. gfw_damage: Pixel mortality severity according to Global Forest Watch. Pixels with wildfires within 1 year of the loss year were masked out before aggregating to 4 km. Data are projected in Web Mercator (EPSG 3857).