Cedros Island is at most some long in N-S direction and wide in the northern half; the southern end is some wide in a NW-SE direction. The island consists of a variety of sedimentary, metamorphic, and igneous rocks, including part of an
ophiolite complex and high-pressure, low temperature
blueschists. Most of the rocks are of Mesozoic age, though some late
Cenozoic strata crop out near the town in the southeastern corner of the island. Its highest peak, Monte Cedros, has an elevation of .
Flora The most common vegetation for more than 90 percent of the land on the island is desert scrub of many different species. The lower elevations, especially the south, receive very sparse rainfall. However, the northern and western parts of the island are often shrouded in fog, and some plants have adapted to receiving moisture from fog. The fog, plus the slightly greater rainfall at higher elevations, has permitted the existence of
Monterey pine forests at elevations of to where the influence of the fog is most intense. The pine forests are scattered and only cover 0.46 percent of the total area of the island. The pines grow to a height of up to .
California juniper are also found at similar altitudes, covering 0.05 percent of the land area. At the highest elevations of the island, above and mixed in with the pine forests,
chaparral vegetation is found. The chaparral averages in height and consists of several woody species including
Quercus cedrosensis, the Cedar Island live oak. Chaparral covers 2.4 percent of the land area of Cedros Island. Vargas or El Aguaje de Vargas is the most important spring, with a flow of 180 drums of 200 L or 55 US gal every 12 hours; springs on the island are usually marked by groves of palm trees.
Fauna Large
sea lion colonies are found on the rocks on the west side as well as the anchorage on the north end. There are feral
goats on Cedros. Unlike on other islands in the region (notably
Guadalupe Island), they do not seem to have had a significant impact on the island ecosystem. This would be due to the fact that Cedros is on the
continental shelf close to the coast and, at least temporarily, it was connected to the mainland during the
last ice age when
sea levels were lower than today. Then, and as a consequence of this, there are native Cedros
herbivores, such as
Cedros Island mule deer which on one hand compete with the goat population for food and presumably have kept it from increasing beyond
carrying capacity, and on the other hand forced the native plants to keep their defenses against herbivores, unlike plants on islands without
megaherbivores, which tend to lack those defenses. Fish are abundant around Cedros Island.
California yellowtail, a subspecies of
yellowtail amberjack, are very plentiful in the waters around the island, as it is their breeding ground. These fish like to live in the kelp beds of the island. Other fish, such as
calico bass and
sheepshead are also very plentiful near the island.
Endemism Cedros Island is home to a number of
taxa that are
endemic or occur in very few places outside the island. These include: ;Animals: • Cedros side-blotched lizard,
Uta stansburiana concinna – endemic • Cedros Island
Bewick's wren,
Thryomanes bewickii cerroensis – near-endemic •
Cedros Island mule deer,
Odocoileus hemionus cerrosensis – endemic • Cedros Island
brush rabbit,
Sylvilagus bachmani cerrosensis – endemic • Cedros Island
cactus mouse,
Peromyscus eremicus cedrosensis – endemic ;Plants: •
Cryptantha maritima var.
cedrosensis – endemic •
Dudleya cedrosensis – endemic •
Dudleya pachyphytum (Cedros Island Liveforever) – endemic •
Eriogonum molle (Cedros soft buckwheat) – endemic •
Ferocactus chrysacanthus – endemic •
Harfordia macroptera ssp. fruticosa – endemic •
Linanthus veatchii – endemic •
Lotus cedrosensis – endemic •
Mammillaria goodridgei var. goodridgei – endemic •
Mammillaria goodridgei var. rectispina – endemic •
Diplacus stellatus – endemic •
Monardella thymifolia – endemic •
Penstemon cerrosensis (Cedros Island penstemon) – endemic •
Pinus radiata var. binata (Guadalupe Island Monterey pine) – near-endemic;
possibly separable as var./ssp. cedrosensis
and in this case endemic. •
Porophyllum cedrense – endemic •
Quercus cedrosensis (Cedros Island oak) — near-endemic •
Rhus integrifolia var.
cedrosensis – endemic •
Salvia cedrosensis (Cedros Island sage) – endemic •
Senecio cedrosensis – endemic •
Verbesina hastata – endemic •
Xylonagra arborea ssp.
arborea – endemic ==See also==