The James San Jacinto Mountains and Oasis de los Osos Reserves are part of the
University of California’s Natural Reserve System (UCNRS). With over 750,000 acres and 39 protected biological field stations that are dedicated “to contribute to the understanding and wise stewardship of the Earth and its natural systems by supporting university-level teaching, research, and public service” the UCNRS is world’s largest reserve system managed by a university. The James San Jacinto Mountains and Oasis de los Osos Reserves are administered by the UC Riverside campus.
The James San Jacinto Mountains Reserve is part of a large forested “sky island” and a jewel of biodiversity. Nested between 5,325 and 5,550 feet in elevation, the James San Jacinto Mountains Reserve is exposed to the extremes of all seasons, it receives on average over 26 inches of annual precipitation, and is surrounded by the most diverse biomes. For these reasons the James Reserve flora is unique with elements from Baja California (South), Colorado Desert (East), Sierra Nevada (North), and the Pacific Ocean (West).
In contrast, the Oasis de los Osos Reserve is located on the lower north side of the San Jacintos between 1,350 and 2,150 feet in elevation and it has a mixture of both maritime Mediterranean and continental desert climate regimes. It lies within the Colorado Desert with the dominant vegetation being desert shrubs and grasses. Although it receives on average only 13 inches of rain a perennial water body -Lamb Creek- runs down from the North slope of the San Jacinto Peak allowing the presence of a permanent riparian zone. The contrasting habitat types result in a great diversity of plants and animals ranging from aquatic to desert species. Two rare species, the Laguna Mountain Springsnail, Pyrgulopsis californiensis, and the giant stream orchid, Epipactis gigantea, are found along the creek.