For more information, see the Terrestrial Endemic Species Index Factsheet at https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=150816. The terrestrial irreplaceability summary depicts the areas of highest irreplaceability within each ecoregion across the state. To achieve this, the data was normalized by taxonomic group and by ecoregion (see Data Sources and Models Used, below). The terrestrial irreplaceability by taxonomic group layers give a statewide overview of irreplaceability for each individual taxonomic group, showing counts of rare endemic species per hexagon and irreplaceability weights (RWI values) for amphibians, birds, mammals, plants, and reptiles. The user can view a list of species potentially present in each hexagon in the ACE online map viewer https://apps.wildlife.ca.gov/ace/. Note that the names of some rare or endemic species, such as those at risk of over-collection, have been suppressed from the list of species names per hexagon, but are still included in the species counts. The California Department of Fish and Wildlife’s (CDFW) Areas of Conservation Emphasis (ACE) is a compilation and analysis of the best-available statewide spatial information in California on biodiversity, rarity and endemism, harvested species, significant habitats, connectivity and wildlife movement, climate vulnerability, climate refugia, and other relevant data (e.g., other conservation priorities such as those identified in the State Wildlife Action Plan (SWAP), stressors, land ownership). ACE addresses both terrestrial and aquatic data. The ACE model combines and analyzes terrestrial information in a 2.5 square mile hexagon grid and aquatic information at the HUC12 watershed level across the state to produce a series of maps for use in non-regulatory evaluation of conservation priorities in California. The model addresses as many of CDFWs statewide conservation and recreational mandates as feasible using high quality data sources. High value areas statewide and in each USDA Ecoregion were identified. The ACE maps and data can be viewed in the ACE online map viewer, or downloaded for use in ArcGIS. For more detailed information see https://www.wildlife.ca.gov/Data/Analysis/ACE and https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=24326.