In the early 20th century, Claremont Canyon was used primarily for cattle grazing, growing eucalyptus plantations, and as a thoroughfare connecting Alameda and Contra Costa counties. Midway up the canyon was a water reservoir until the early 1920s. Over the years, as land ownership gradually transferred to the East Bay Regional Park District, the University of California, and other public agencies, the 500-acre watershed evolved into a mostly undeveloped wildland, with private homes nestled against its southern ridge.
The wildland landscape is currently a mosaic of vegetation types, mostly north coastal scrub and oak/bay woodlands, but also scattered grasslands, a few 100-year-old eucalyptus plantations, and a 40-year old redwood restoration area (which was augmented with new seedlings planted in the early 2000's).
According to the East Bay Regional Park District, nearly 400 plant species, both native and introduced, have been reported in Claremont Canyon. Wilde Legard’s 2014 photographic guide to Wild Plants of Claremont Canyon Regional Preserve shows about 225 plants; though most of the photos were taken elsewhere on Park District land. Legard's earlier 2007 photographic guide Claremont Canyon Wildflowers displays about 115 'showy wildflowers;' again, most photos taken elsewhere in the District. Also see Claremont Canyon Checklist of Wild Plants, Sorted Alphabetically by Growth Form, Scientific Name, on the District's website.
With varied plant communities and limited human development, Claremont Canyon hosts a variety of wildlife. Commonly seen are the eastern fox squirrel, black-tailed deer, raccoon, coyote, gray fox, fence lizard and garter snake, as well as a large variety of birds and insects, both resident and transient.
The website Wild Life in the North Hills, by long-time resident Kay Loughman, includes a photo gallery and listings of wildlife and plants in Claremont Canyon and its adjacent neighborhoods. Nearly 3000 photos taken by more than 100 local photographers document flora and fauna, including birds, butterflies, mammals, reptiles, plants, fungi, and lichens. Since 1993, the site has documented with a photo: 101 birds, 59 butterflies and moths, 63 other invertebrates, 17 mammals and marsupials, 16 amphibians and reptiles, 242 plants, 65 mushrooms, and 87 lichens. Additional species have been reported, but not photographed.