The La Sierra Preserve is in the Santa Monica Mountains in an unincorporated area of Los Angeles County roughly situated between the City of Agoura Hills to the north and the City of Malibu to the south. MRT, in partnership with Los Angeles County, maintains, restores, and manages the 130 acre La Sierra Preserve. The La Sierra Preserve is part of a larger area designated as a SEA based on the presence of natural habitat supporting rare, threatened or endangered plant and animal species. Locally uncommon plants found in abundance on the preserve include the Humboldt lily, chain fern, maidenhair fern, black cottonwood, leather root, bigleaf maple, smooth dogwood and broadleaf lupine. The more general plant community within La Sierra is comprised of mixed chaparral and maple-bay-oak-sycamore-willow riparian woodland. Within the surrounding watershed, mainly on the southwest slopes, there are several water features including perennial streams (in non-drought years), ephemeral streams, seeps and vernal pools. Relatively undisturbed wetland and riparian environments such as these are very rare in Southern California, making the protection of La Sierra environmentally important.
La Sierra is a prime wildlife habitat, biologically diverse, and rich in willow riparian habitat, oak woodland, mixed riparian woodland, coastal sage scrub, wetlands, grassland, and chaparral. La Sierra provides habitat linkages to springs, seeps, and wetland areas that are critical to wildlife in the Malibu Creek watershed.