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Natural History

Hollister Hills SVRA is home to many species of plants and animals, including California tiger salamander and California red-legged frog, both federally-listed as threatened, and Gairdner’s yampah, western azaleas, a variety of hawks, mountain lions, and more. The park’s commitment to protecting these species, while providing high-quality sustainable OHV recreation opportunities, requires active resource management. Park staff is constantly working to improve trail design, monitor wildlife habitat, implement erosion control measures, maintain roads and trails, suppress excessive dust, protect riparian areas, and address invasive plant and animal species within the park. Managing natural and cultural resources requires constant vigilance. Throughout the park you may encounter trail reroutes, fencing, gates, and/or closed areas.

Please do your part to ensure that Hollister Hills SVRA will be available to you and future generations by staying on trails, respecting wildlife, and staying out of vegetated and closed areas.

San Andreas Fault
Cutting northwest through the park, the San Andreas Fault zone defines the tectonic boundary between the North American and Pacific plates, marking a divide between two contrasting terrains. The area east of the fault has dark, clay-rich soils on rolling hills covered in grassland and oak woodlands. This portion of the park sits on the North American plate and is slowly moving south. West of the fault, the landscape is higher and steeper and sits on the Pacific plate that is moving north. This portion of the park consists primarily of much older and more weather-resistant granitic rock, with pine, sage and chaparral taking root in the sandy soils. The Pacific and North American tectonic plates have been sliding past each other for 30 million years at a current rate of about 1.5 inches per year.