California has more than 34 million registered vehicles, 156,000 miles of roadway, ranks seventh in the U.S. for public lands, and contains the nation's highest level of biodiversity, including species diversity, risk level, endemism and total extinctions. Roads and highways impact wildlife directly through wildlife-vehicle collisions (WVC) and indirectly by cutting off the movement of plants, fish, birds and wildlife. Economic costs associated with these collisions in California are approximately $300 million each year.
Despite the threat posed to both humans and wildlife from ongoing collisions and loss of connected habitat, the data on WVCs, or roadkill, have been collected in an uneven and often haphazard manner with California's most extensive data collection effort, California Roadkill Observation System, including observations on only ~10% of the state's roadways. Most states have similarly incomplete surveys of roadkill and where data collection is more thorough, it tends to be for larger mammals and not all other taxa.
This WVC data can be used to identify highway segments where wildlife movements are important to consider in transportation planning, project development, regulatory permitting and operation of the transportation system. Such information should be integrated with other information that state DOTs and local agencies use to establish priorities for ensuring that investments in new and improved transportation facilities will result in wildlife-friendlier transportation systems.
Formalizing how WVC data are collected and managed, the analyses of these data, and the use in formal decision-making is an important step in making WVC mitigation more systematic. We will discuss specifications for WVC reporting systems, including data formats, data tracking and verification, data management, security and sharing, and other requirements for WVC informatics. We will present methods for analyzing WVC datasets to estimate total impact of roadkill on wildlife and for large areas. We will also describe how WVC data can and has been used to support mitigation decisions, from the level of analysis to combining with other types of data and supporting specific mitigation decisions. Finally, we will discuss the varied promises/benefits of partnerships, policy and programmed funds for mitigating WVC impacts to drivers and wildlife populations.