Terrestrial Habitat Connectivity

In 2018, the California Biodiversity Initiative Roadmap (PDF) directed CDFW to develop an updated statewide habitat connectivity map. To accomplish this, CDFW compiled available regional linkage models along with California Essential Habitat Connectivity (CEHC) linkages developed at a statewide scale(Spencer et al. 2010). Other data sources informing this effort include Terrestrial Landscape Intactness (Degagne et al. 2016) which provides an index of multiple anthropogenic disturbances, and Omniscape, an ecological flow model (TNC and CSP 2018). The resulting Statewide Terrestrial Connectivity map (PDF), part of the CDFW Areas of Conservation Emphasis (ACE) project, presents a view of connectivity across the state using the ACE hexagon grid, a statewide tessellation of 2.5 sq. mile hexagons. Each hexagon contains attributes identified across multiple studies, and is then assigned to one of five ACE connectivity classes and accompanying ranks, indicating the relative importance of each area to providing opportunities for the movement and dispersal of organisms critical to maintaining healthy populations and species survival.

Factsheet: Terrestrial Connectivity [ds2734] (PDF)

As with all ACE model products, the Terrestrial Connectivity Map represents a snapshot in time. CDFW is currently working to fill remaining data gaps with additional fine-scale linkage studies across the state and modeling corridors of large, highly mobile species using GPS collar data. The map will be updated over time as new data become available.

ACE datasets as well as statewide and regional connectivity datasets are available for viewing and download through BIOS, the CDFW spatial data library and interactive viewer. CDFW Fish Passage Priority datasets are also available. This data has been preloaded into specially curated versions of the BIOS data viewer, accessible through the above links.

References

Spencer, W.D., P. Beier, K. Penrod, K. Winters, C. Paulman, H. Rustigian-Romsos, J. Strittholt, M. Parisi, and A. Pettler. 2010. California Essential Habitat Connectivity Project: A Strategy for Conserving a Connected California. Prepared for California Department of Transportation, California Department of Fish and Game, and Federal Highways Administration.

Degagne, R., J. Brice, M. Gough, T. Sheehan, and J. Strittholt. Terrestrial Landscape Intactness 1 km, California. Conservation Biology Institute, December 2016.

The Nature Conservancy (TNC), California Chapter and Conservation Science Partners (CSP), 2018. TNC Omniscape Connectivity Web Map. 

The terrestrial wildlife barrier priorities dataset represents CDFW's ongoing effort to identify wildlife movement barriers across the state.

Wildlife habitat connectivity is understood to be an important mechanism of maintaining biodiversity in the face of human population growth and climate change. Listing priority wildlife barrier locations helps focus limited resources where the highest needs have been identified to improve wildlife movement. The terrestrial wildlife barrier priorities are complementary to CDFW's fish passage barrier priorities that have been identified for anadromous fish. These barrier priorities are periodically updated to reflect new information and barrier removal successes. Additional information and tools for exploring the fish Passage Assessment Database (PAD) are available through the CDFW data portal.

CDFW divides the state into six administrative regions where staff identified linear segments of infrastructure that currently present barriers to wildlife populations in their jurisdictions. Regional staff used all available data, including connectivity and road crossing studies, collared-animal movement data, roadkill observations, and professional expertise. This dataset represents all barriers identified statewide as of May 2022 and former barriers that have been remediated since 2020. Most of the barriers identified are highway segments, but other infrastructure types such as railways, high-speed rail alignments, canals, local roads, and fencing are also represented.

Reports

• Restoring California's Wildlife Connectivity 2022 (PDF)
• California Wildlife Barriers 2020 (PDF)

California is home to several species of ungulates, including mule deer, elk, pronghorn, and bighorn sheep. Many of the ungulate herds in California are migratory and require large landscapes to persist, making them particularly vulnerable to habitat loss and fragmentation. Connectivity between seasonal ranges is therefore crucial to conserve these charismatic species and to facilitate their movement across the landscape. In addition to migration corridors, mapping and conserving high-use winter range habitat is also essential to maintain ungulate herd population viability.

In 2020, efforts began to analyze GPS collar datasets that provide accurate location information for ungulate individuals over time. Using this collar data from historical and ongoing projects across the state, ungulate population-level corridors, stopovers, and winter range habitats are being mapped and prioritized for conservation.

This interactive story map explores many of CDFW's ungulate migration products, describing the data and analytical processes. A complete list of ungulate migration products available to the public can be viewed in the Ungulate Migration Corridor Viewer, a specially curated version of BIOS, CDFW's spatial data library and viewer.

Reports*

• Ungulate Migrations of the Western United States, Volume 1
• Ungulate Migrations of the Western United States, Volume 2
• Ungulate Migrations of the Western United States, Volume 3

*California ungulate herds are represented in this series beginning with Volume 2.

In 2012, CDFW began a project funded by the Wildlife Conservation Board to map wildlife connectivity areas in the northern Sierra Nevada foothills (NSNF). The project:

• Analyzed connectivity within the NSNF and between the NSNF and adjacent lands in the Central Valley and Sierra Nevada using the NSNF fine-scale vegetation map recently completed by the Vegetation Classification and Mapping Program, and following recommendations from the statewide California Essential Habitat Connectivity project,
• Identified important core habitat areas for focal species and use species-specific data to model corridors between blocks of protected lands,
• Identified land facets, areas of land with uniform topographic and geologic features that will interact with future climate to support species and species movement under future climate conditions,
• Developed guidance on minimum standards for fine-scale connectivity modeling needed to meet the CDFW mission and mandates.

Reports

• Final Technical Report, January 2015 (PDF)
• Guidance Document for Fine-Scale Wildlife Connectivity Analysis, December 2014 (PDF)

Additional Information

• Project information sheet (PDF)
• Focal species list (PDF)
• Project study area (PDF)
• Conservation partners meeting presentation (PDF)