San Clemente Island

Map Satellite

Biologically this island is one of the richest areas in the State, despite the depredations by introduced goats, pigs and cats.

A total of 311 vascular plants has been collected on the island, of which 243 are presumed indigenous. Of this total, 14 are restricted to San Clemente Island and an additional 29 are known only from here and the other California islands. Among those found exclusively on the island are Astragalus nevinii, Brodiaea kinkiensis, Camissonia guadalupensis ssp. clementina, Castilleja grisea, Eriogonum giganteum ssp. formosum, Galium catalinense ssp. acrispum, Lotus dendroideus var. traskiae, and Stephanomeria blairii. Only a few plants of the mallow Malacothamnus clementinus survive (in a dump where the goats cannot go). Lithophragma maximum and Lotus argophyllus var. adsurgens have not been collected for a number of years and may be extinct.

Coastal sage scrub and chaparral are the dominant communities. On a plateau near Thirst there is an extensive stand of relatively uncontaminated Nassella pulchra. Off The Hook there are fringing kelp beds with seaweeds growing down to approximately 50 meters (200 feet), perhaps the deepest site in Southern California.

Zoologically the island is depauperate. The native island fox, Urocyon littoralis, appears to have its nearest relative among the Central American foxes. Of the two reptiles, both lizards, found on the island, the monotypic Klauberina riversiana is a relict; other members of the family Xantusiidae appear to derive from an ancestor similar to Klauberina. The Northern elephant seal, Mirpunga angustirostris, and the California sea lion, Zalophus californianus, have breeding rookeries here. Other pinnipeds use the island as a hauling ground.

At least two snail species, Micrarionta redimita and Micrarionta intercisa, are found only here.

The island is composed primarily of Miocene andesitic volcanic flows and pyroclastic sequences. Its most significant geological features are the marine terraces and sand dunes. Over 20 terraces have been identified below the 450-meter (1,500-foot) level and they form some of the most extensive and best examples found anywhere along the West Coast. There are considerable areas of active or recently active sand dunes, some with sand molds of tree trunks and limbs. Several fossil sites containing both marine vertebrates and invertebrates are found on the island including those at Horse Cove and the nearby South Basin. The marine vertebrates are related to the Sharktooth Hill fauna (see Shark Tooth Hill).

Integrity: Present development includes several dirt roads, some buildings and an airstrip. The island has been heavily overgrazed and the feral goats have materially altered the flora and have led or will lead to the extinction of several species.

Use: Present, research and education. It is strongly recommended that the feral goats and cats be removed.

Ref:

Raven, P. H., 1963. A Flora of San Clemente Island, Calif. Aliso Vol. 6, No. 1, p. 11.

Thorne, R. F., 1969. A Supplement to the Floras of Santa Catalina and San Clemente Islands, Los Angeles County, California. Aliso Vol. 7, No. 1, p. 73-83.

Philbrick, Ralph N. (ed.), 1967. Proceedings of the Symposium on the Biology of the California Islands, Santa Barbara Botanic Garden, Santa Barbara, 363 pp.

February 1975