The Santa Rosa Plateau, with an average elevation of 2,000 feet, is located at the southern end of the Santa Ana Mountains in southwestern Riverside County, California. Ancient oak woodlands, rare bunchgrass prairie, and aromatic coastal sage scrub are a few of the plant communities that reside on this land located less than 20 miles from the Pacific Ocean.
The Plateau’s mild climate made the area an ideal habitat for people, beginning thousands of years ago with the arrival of Native Americans. Ancestors of local American Indians, known today as the Luiseno, harvested and hunted the oaks and mule deer that are still found on the land today. This hunting and gathering way of life came to an end on the Plateau in the 1820′s with the secularization of mission lands.
The Santa Rosa Plateau became Rancho Santa Rosa under a 47,000 acre 1846 Mexican land grant to cattle and sheep rancher Juan Moreno. In 1855, Senor Moreno sold his ranch to land-grantee neighbor Augustin Machado (owner of the Rancho La Laguna, today the Lake Elsinore area) for one thousand American dollars. The Moreno and Machado adobes still stand as the oldest structures in Riverside County.
The ranch passed from owner to owner until 1904, when the Vails, a ranching family from Arizona, purchased the Santa Rosa, plus much of what was to become Murrieta and Temecula. They continued to operate their large cattle ranch for the next sixty years. Fortunately, for the sensitive habitats on the Plateau, the Vails were wise stewards of their property. They kept the number of head per acre to a sustainable amount, and only grazed during the wet months, moving the cattle down to valley feed lots when the dry summer season arrived. The grazing practices of the Vail Ranch management may be the reason the Plateau is considered by many to be the finest remaining example of a once widely-scattered California bunchgrass prairie system.
In 1964, the Vails sold the ranch to the Kaiser Steel Company, which master-planned Rancho California – the communities that today comprise the cities of Temecula and Murrieta. In the first two decades of that era, grazing leases allowed cattle operators to continue to use the Plateau. Overgrazing and year-round use caused habitat deterioration during that twenty-year period, including the formation of deep erosion channels along the Plateau’s main creeks.
In 1984, The Nature Conservancy of California, recognizing the intense concentration of unique and rare species supported on the Plateau lands, purchased 3,100 acres in two parcels from the owner, KACOR (a subsidiary of Kaiser Steel). The intervening lands were targeted for later conservation purchase.
In the late 1980′s, however, Ranpac Inc. of Temecula purchased 4,000 acres comprising most of the intervening lands and prepared a specific plan for approximately 4,000 homes. A citizens group, Preserve Our Plateau, formed to try and protect the property from development. Purchase money was sought to buy the land back from Ranpac, who was agreeable to a sale. Awareness and moral support was widespread, but funds were scarce; county, state and national agencies were unable to secure enough for a purchase.
Seeking extensive and significant off-site mitigation opportunities for a new, large storage reservoir planned in the region, Metropolitan Water District of Southern California (MWD) approached the organization with an offer to provide $15.4 million towards a purchase in exchange for mitigation credits for their future Eastside Reservoir Project. The County of Riverside nearly matched that funding with $15 million; the State of California’s Wildlife Conservation Board provided $5 million from Proposition 117 (Mountain Lion Initiative) funds. The Nature Conservancy handled negotiations and provided closing costs. Each entity purchased its own property, but the entire site – known collectively as the Santa Rosa Plateau Ecological Reserve – is managed as one biological unit.
The four landowners (the state, county, MWD, and The Nature Conservancy), and the U.S. Fish and Wildlife Service (which owns no land on the Plateau, but has an interest in its rare and endangered species) signed a cooperative management agreement and today meet monthly to oversee management of the Reserve. Biological resource management, including a prescribed fire program and habitat restoration, is conducted by The Nature Conservancy while visitor management, including a Visitor Center and 40-mile trail system, is conducted by Riverside County Regional Park and Open-Space District. Metropolitan Water District of Southern California provides an education grant which allows over 5,000 local grade school children to visit and become inspired by one of their communities most outstanding resources.
Additional purchases have now expanded the Plateau’s protected size to nearly 8,500 acres. Annually, more than 40,000 day-use visitors travel to the Reserve for hiking, nature study, photography, etc. Visitors may also use designated trails for horseback riding and mountain biking.
Of the more than 120 sensitive species of plants and animals in the Inland Empire, 59 of them can be found on the Santa Rosa Plateau. Red-legged frogs, California newts, and southwestern pond turtles survive in bedrock-lined pools of the stream system, much of which is under restoration. Native wildflowers, some nationally endangered, draw thousands of spring visitors. Vernal pools, the seasonal, shallow ponds which collect on rare volcanic soils, support endemic fairy shrimp and wintering waterfowl. Engelmann oaks, a vanishing, simi-deciduous species with blue-gray leaves and contorted branches, are found in abundance among the rolling grasslands. Badgers, horned lizards, mountain lions, bobcats, gray fox and deer are found on the Plateau, as are more than 180 species of birds.