Forest to Grass/Shrub transformation in the Western US from 2001-2012

This data release contains three raster layers that identify pixels of persistent forest-to-grass/shrub land cover change. The layers were derived from annual Land Change Monitoring, Assessment, and Projection (LCMAP) Land Cover Primary (LCPRI) rasters for 1985-2021. A pixel qualifies when (1) it is classified as Tree Cover (class 4) in the start year, 2001, and (2) at any point after 2001 it spends at least 10 consecutive years in Grass/Shrub (class 3). The qualifying run does not need to begin immediately after 2001 or to continue through 2021. The release includes a binary qualification layer, a layer giving the longest consecutive run (in years) spent in Grass/Shrub after 2001, and a layer giving the first year of the qualifying run. The rule was applied pixel by pixel using windowed, multithreaded processing in Python so that the full annual stack never has to be held in memory. To map areas where forest (Tree Cover) was converted to, and remained in, grass/shrub cover for a sustained period, for use in land cover change analysis we used before parameterization. Rule parameters: START_YEAR = 2001; PERSISTENCE_YEARS = 10; CLASS_FOREST = 4 (LCMAP Tree Cover); CLASS_GRASS = 3 (LCMAP Grass/Shrub). Because only years after 2001 are scanned for the run (2002-2021), the longest possible run is 20 years and a qualifying run can start no later than 2012. Land cover classes between the start year and the qualifying run are not restricted, so a pixel may pass through other classes before its grass/shrub run begins. An optional, stricter rule (REQUIRE_STABLE_BACK_TO_FIRST_YEAR = True) additionally requires Tree Cover in every year from 1985 through 2001; it was NOT used for the released layers unless stated otherwise by the author.