The Irvine Open Space Preserve is part of the historic Irvine Ranch, which has been officially designated as a Natural Landmark by both the State of California and the United States Department of the Interior, in recognition of the exceptional value of the biological and geological resources found on these lands.

In 2006, nearly 37,000 acres of the Irvine Ranch were selected as a National Natural Landmark (NNL), a designation which reflects the outstanding condition, rarity, diversity and value to science and education of the natural resources on the land. During a rigorous independent study of the land by a group of accomplished scientists selected by the National Park Service, geologists identified many intact features that illustrate a complete geologic history of the southwestern continental margin of North America – from the late Cretaceous period (65 to 80 million years ago) to the present. The land’s biological resources are perhaps even more valuable, as they include rare contiguous expanses of threatened coastal sage scrub and chaparral habitats, within which are located populations of endangered plants and animals such as the California gnatcatcher, peregrine falcon and Pacific pocket mouse.

The beautiful, diverse natural landscape of the historic Irvine Ranch were also selected in 2008 as a California Natural Landmark (CNL), a designation given to the areas that best illustrate the biological and geological character of the state and strengthen public appreciation for natural history and conservation. These outstanding examples of our region’s natural resources can be explored in areas protected and managed by local agencies, including: Crystal Cove State Park (California State Parks); Laguna Coast Wilderness Park (OC Parks); Weir, Limestone, and Fremont Canyons Wilderness Areas (OC Parks); Upper Newport Bay (OC Parks and City of Newport Beach); San Joaquin Wildlife Sanctuary (Irvine Ranch Water District); and Orchard Hills, Quail Hill, Shady Canyon, and Bommer Canyon Preserve (City of Irvine). Collectively, these protected wildlands and parks make up a biologically diverse community that provides sanctuary for plants and animal species.

The first application of the State of California’s Natural Community Conservation Planning (NCCP)/Habitat Conservation Planning (HCP) Programs in the Central and Coastal Subregion of Orange County was the establishment of the Nature Reserve of Orange County (NROC), a 37,000-acre area designed to protect the habitat of coastal sage scrub communities and the three target species found predominantly in this habitat: the California gnatcatcher, the cactus wren and the orange-throated whiptail lizard. This multiple-species, multiple-habitat Reserve also provides for protection of: 7,300 acres of chaparral; 6,100 acres of grassland; 1,800 acres of riparian; 950 acres of woodland; and significant portions of other habitats that currently exist within the subregion. The Irvine Open Space Preserve represents the second-largest piece of the Reserve (in acres), eclipsed only by the County of Orange’s many wildland parks and conservation easement lands also enrolled in the Central and Coastal Subregion NCCP program. The preserve provides sanctuary for protected plants and animal species.