California Department of Fish and Wildlife


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Department of Fish & Wildlife
Biogeographic Data Branch

Physical Address:
1700 9th Street, 4th Floor
Sacramento, CA 95811

Mailing Address:
1416 9th Street, Suite 1266
Sacramento, CA 95814

(916) 322-2493 • Email BDB

Areas of Conservation Emphasis (ACE-II)

Areas of Conservation Emphasis (ACE-II) is a Department of Fish and Wildlife project that was started in 2009 to provide data to help guide and inform conservation priorities in California.

*** ACE-II v2 (updated September 2015) is now available! ***

The purpose of ACE-II is to:

  • Compile and analyze the best available statewide, spatial information on California's biological richness, including species diversity, rarity, and sensitive habitats,
  • Integrate these data into a spatial model that can be used to identify areas of biological or conservation interest throughout the state.
  • Develop a set of tools and produce maps that summarize and display this information for use in conservation decision-making.

ACE-II provides an easily-accessible and standardized way to view the best available statewide data on California's biological richness and biodiversity. These datasets have many uses ranging from ecological research and modeling to local land-use planning and conservation decision making. The ACE-II data are dynamic and will be updated periodically as new data warrant.

The ACE-II Biological Richness Model summarizes data on native species richness, rarity, endemism, and sensitive habitats across a statewide, 2.5 square mile hexagon grid. Datasets include native richness, rarity, and endemism for each of six taxonomic groups: birds, fish, amphibians, plants, mammals, and reptiles. Information on the location of four sensitive habitat types, wetlands, riparian, rare upland natural communities, and high value salmonid habitat, is also summarized. The data can be used to view the distribution of biological richness, by individual taxonomic group and overall, across the state (Statewide Model) and within each USDA ecoregion (Ecoregional Models).

Statewide Model

The statewide GIS data layers depict the biological index model results at a statewide scale. The four biological richness indices are calculated relative to the entire state of California: native species richness, rare species richness, “irreplaceability” (i.e., rarity-weighted richness), and the presence of sensitive habitats. These layers were combined in a weighted additive model to produce the ACE II biological index surface showing relative richness and rarity across the state; however, the ecoregional analysis is more suited for local and regional planning.

Ecoregional Model

The ecoregional GIS data layers depict the biological index model results by USDA Ecoregion Section.

The ecoregional analysis combines four biological richness indices, native species richness, rare species richness, “irreplaceability” (i.e., rarity-weighted richness), and the presence of sensitive habitats, in a weighted additive model to produce the ACE II biological index surface. The model results show the areas of highest richness and rarity within each ecoregion of the state. Areas with a high biological index score would be expected to have high conservation value and meet multiple conservation goals, subject to certain assumptions and limitations. A full description of the data collection and modeling process, as well as the assumptions and limitations of this process, is available in the ACE-II Project Report.

Because each ecoregion was analyzed separately; biological index scores are not directly comparable between ecoregions. The model results for individual ecoregions can be displayed in the ACE-II Viewer or are available by request.


  • CDFW Map Viewers are best viewed using Firefox or Chrome.
    The ACE-II Viewer is an on-line, interactive map interface for displaying and manipulating the ACE-II maps, data, and model results. The viewer includes additional spatial data such as stressors, protected status of lands, and connectivity and corridors that can be overlaid on the ACE-II data layers. The viewer tool allows the user to display and contrast the arrangement and relative value of California's unique biological resources, providing a first step toward setting conservation priorities statewide.
  • Statewide and Ecoregional Models: Model results depicting relative biological richness statewide and within each USDA Ecoregion Section can be displayed in the viewer or are available for download (see GIS Data below).
  • Weighted-additive model interface: A component of the ACE-II Interactive Viewer that allows the user to adjust the weights of the various layers and display a customized model result.
  • GIS Data: All spatial data layers can be displayed in the viewer or are available for download by following the instructions below.

GIS Data Download

Please refer to the ACE-II Project Report for an explanation of the data development and intended use prior to downloading the data.

The ACEII data is a very complex and dynamic data set. It will be updated as Department needs are identified, so we recommend checking back with us from time to time for updates. It is also an unsupported data set so we strongly encourage you to read all of the documentation and access the data through the online ACE viewer when possible.

Download GIS Data

Reports and Further Information

Related Efforts

ACE-II is a component of a larger effort to plan for the conservation and management of California's resources at a landscape scale, which includes the California Wildlife: Conservation Challenges, California's Wildlife Action Plan; the California Climate Adaptation Strategy; and large-scale, multi-species conservation plans. The ACE-II products are complementary to the California Essential Habitat Connectivity Project, which identified large remaining blocks of intact habitat in California and modeled corridor linkages between these blocks. In addition, ACE-II is one building block in a long-term collaboration of 18 western states to develop robust Decision Support Systems for conservation planning.

For multi-state analysis, please visit the Western Governors' Crucial Habitat Assessment Tools (CHAT) website where a similar product is presented for California, in the context of the surrounding states. Please read our Comparison of CHAT and ACE-II document to better understand how these products differ.

Contact Information

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