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Areas of Conservation Emphasis (ACE)

What is ACE?

ACE is a CDFW effort to analyze large amounts of map-based data in a targeted, strategic way, and expressed visually, so decisions can be informed around important goals like conservation of biodiversity, habitat connectivity, and climate change resiliency. The ACE maps provide a coarse level view of information for conservation planning purposes, ranging from ecological research and modeling to local land-use planning and conservation decision-making. However, they do not replace the need for site-specific evaluation of biological resources and should not be used for regulatory purposes.

All ACE data layers are limited by the accuracy, scale, extent of coverage, and completeness of the input data at the time they were run. We highly recommend reviewing available metadata and ACE Factsheets (found in the folders below) prior to interpreting these data. The ACE data are dynamic and will be updated periodically as new data warrant. A new and improved version, ACE 3.0, was released in February 2018, and we welcome feedback on this latest version.

ACE data structure Species Biodiversity Significant Habitats Connectivity Climate Resilience Recreation


ACE was a CDFW Project first developed in 2009 with the purpose of providing an easily-accessible and standardized way to view a mapped summary of the best available statewide data on California's biological richness and biodiversity for use in conservation planning. ACE relies on other CDFW mapped data products including CNDDB, CWHR, and Survey of California Vegetation, as well as other mapped information found in BIOS as sources for these summarized maps. In early 2017, CDFW began an effort to improve and expand on this concept by incorporating new data, data models, and summarized information. ACE version 3.0 is now available.

The previous version of ACE primarily focused on a synthesized summary of species biodiversity, rarity, and significant habitats referred to as the “Biological Index”. Modifications to this basic format were identified based on user feedback and the availability of new information. ACE version 3.0 now includes four distinct biological summaries: Species Biodiversity, Significant Habitats, Habitat Connectivity, and predicted Climate Resilience. These summaries were developed for Terrestrial Ecosystems within each USDA Ecoregional section of the State using a 2.5 square mile-hexagon grid format and for Aquatic Ecosystems based on watersheds using hydrological units at the 12-digit code level (HUC12). The terrestrial and aquatic biodiversity summaries were combined to provide a summary of statewide biodiversity.This version of ACE also provides access to additional datasets that have been deemed useful in conservation planning, and to support recreational planning as it pertains to wildlife resources. The State Wildlife Action Plan (2015) conservation targets are also mapped and now available in ACE. Work on datasets to include in some of these categories is continuing, which once completed and combined with other datasets will provide additional data summaries. This new information will be reflected in future updates of ACE as they become available. We welcome feedback regarding the data sets and the ACE viewer.

Species Biodiversity

terrestrial biodiversity icon aquatic biodiversity icon

Species Biodiversity Summaries combine the three measures of biodiversity developed for ACE into a single metric. These three measures include: 1) native species richness, which represents overall native diversity of all species in the state, both common and rare, as well as climate vulnerable species and important game and sport fish species; 2) rare species richness, which represents diversity of rare species; and, 3) irreplaceability, which is a weighted measure of endemism that highlights areas that support unique species of limited range. Terrestrial Datasets include native richness, rarity, and irreplaceability for each of five taxonomic groups: birds, amphibians, plants, mammals, and reptiles. While the Aquatic Datasets include native richness, rarity, and irreplaceability for each of four taxonomic groups: fish, aquatic invertebrates, aquatic amphibians, and aquatic reptiles. The data can be used to view the distribution of biological richness by individual taxonomic group and overall, within each USDA ecoregion (terrestrial) and across the state’s watersheds (aquatic). Users can view a list of species that contribute to the biodiversity measures for each hexagon (for terrestrial species) or watershed (for aquatic species) by selecting the layer called Terrestrial Species List and Aquatic Species List, respectively. Further information is available in the dataset factsheets.

Dataset Factsheets:

link opens in new windowBiodiversity Summary [ds2769] (PDF)

terrestrial biodiversity icon aquatic biodiversity icon
link opens in new windowTerrestrial Biodiversity Summary [ds2739] (PDF) link opens in new windowAquatic Biodiversity Summary [ds2768] (PDF)
link opens in new windowTerrestrial Native Species Richness [ds2703] (PDF) link opens in new windowAquatic Native Species Richness [ds2743] (PDF)
link opens in new windowTerrestrial Rare Species [ds2709] (PDF) link opens in new windowAquatic Rare Species [ds2748] (PDF)
link opens in new windowTerrestrial Irreplaceability [ds2715] (PDF) link opens in new windowAquatic Irreplaceability [ds2752] (PDF)

Significant Habitats

terrestrial habitats icon  aquatic habitats icon

The Significant Habitat datasets provide a variety of information on aquatic and terrestrial habitats to help determine the likelihood of the presence of habitat or vegetation that are the focus of state, national, or locally legislated conservation laws, as well as significant habitat areas essential to the survival of specific species of conservation concern. Habitat data are synthesized from information on vegetation and land cover, and species-specific habitat information. The attribute tables in the viewer for the Significant Terrestrial Habitat Summary and Significant Aquatic Habitat Summary provide the number of significant habitats in a hexagon or watershed, respectively, as well as references to the original datasets where each significant habitat element is mapped.

The Significant Habitats datasets are expected to be used along with other ACE datasets to provide a robust assessment of the presence and relative importance of elements important for biodiversity conservation.

Dataset Factsheets and Datasets:

terrestrial habitats icon aquatic habitats icon
link opens in new windowTerrestrial Significant Habitats Summary [ds2721] (PDF) link opens in new windowAquatic Significant Habitats Summary [ds2756] (PDF)
Rare Vegetation Types [ds2722] Anadromous Habitat [ds2759]
Oak Woodlands [ds2723] Lakes by Watershed [ds2762]
Riparian [ds2724] Riparian by Watershed [ds2758]
Freshwater Wetlands [ds2725] Freshwater Wetlands by Watershed [ds2764]
Saline Wetlands [ds2726] Saline Wetlands by Watershed [ds2766]


terrestrial connectivity icon

The Terrestrial Connectivity dataset summarizes information on terrestrial connectivity per hexagon including the presence of mapped corridors or linkages; the juxtaposition to large, contiguous, natural areas; and the relative intactness score. This dataset was developed to support conservation planning efforts by allowing user to spatially evaluate the relative contribution of an area to terrestrial connectivity based on the results of statewide, regional, and other connectivity analyses. Work on this dataset will continue during 2018. An aquatic equivalent dataset has not yet been developed, but one can refer to the California Fish Passage Assessment Database [ds69] in BIOS for known and potential barriers to anadromous fish.

Factsheet: link opens in new windowTerrestrial Connectivity [ds2734] (PDF)

Climate Resilience

terrestrial climate change icon

The Terrestrial Climate Change Resilience dataset displays the probability that a given location within California will serve as refugia under climate change, summarized by ACE hexagon. These are areas where climate conditions will likely remain suitable for the current array of plants and wildlife that reside within a hexagon, and where ecological functions are more likely to remain intact. This data set was developed to support conservation planning efforts by allowing users to spatially evaluate potential resilience to climate change.

Currently, the dataset is based primarily on link opens in new windowThorne et. al. 2016 (PDF). Work on this dataset will continue during 2018. An aquatic equivalent dataset has not yet been developed.

Factsheet: link opens in new windowTerrestrial Climate Change Resilience [ds2738] (PDF)


recreation icon

CDFW’s mission includes providing Californians with high quality recreational opportunities that involve fish and wildlife. The goal of this component is to provide fish and wildlife recreational use and need information to support the Wildlife Conservation Board and other public access programs. At present, the currently available link opens in new windowrecreation-related information in BIOS is “bookmarked” for such use. Future work will focus on developing additional relevant datasets based on specific needs for incorporation into ACE.

Disadvantaged communities in California are specifically targeted for investments aimed at improving public health, quality of life and economic opportunity in California’s most burdened communities. Several mapping tools are already available on-line. One such tool is the link opens in new windowDAC Mapping Tool, developed by the Department of Water Resources to assist local agencies and other interested parties in evaluating disadvantaged community status throughout the State, using the definition provided by Proposition 84 IRWM Guidelines (2015).

Contact Information

Melanie Gogol-Prokurat
Conservation Analysis Unit Coordinator
Biogeographic Data Branch
(916) 324-9265

Last Updated 02/18/18