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 mostly undeveloped wildlands, with private homes nestled against its southern ridge. By the mid-20th century, as cattle grazing eventually phased out, the distribution of vegetations types changed dramatically.
Currently, the wildland landscape is a mosaic of 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 forest near the top of the canyon (which was augmented with new seedlings planted in the early 2000s (read about it here).
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. Also see Checklist of East Bay Flora, Sorted Alphabetically by Growth Form, Scientific Name, on the District's website.
Janet Gawthrop of the California Native Plant society describes plants in sunny and shady locations of Claremont Canyon in this charming 2020 article.
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. Of great interest, but rarely seen, is the Alameda whipsnake (Masticophis lateralis euryxanthus). This elusive and speedy snake is protected at the state and federal level. Claremont Canyon Regional Preserve is hosting a research project focused on the Alameda whipsnake, sometimes referred to as the Alameda striped racer (Coluber lateralis euryxanthus).
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 3,000 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.