Santa Cruz Island

source: billdeweyphoto.com

Santa Cruz Island is the largest privately owned island off the Continental United States. The island encompasses 96 square miles or about 62,000 acres and is approximately 22 miles long. For comparison, it is over four times the size of Manhattan (22 square miles) or Bermuda (19 square miles), and is larger that the District of Columbia (61 square miles) and over four times the size of Manhattan! It is in Santa Barbara County and is the only island owned to the water’s edge at all times, as stated in its original 1839 grant from Governor Alvarado to Andres Castillero, the island’s first private owner from 1839 to 1857.

Flora and Fauna

There are only four native terrestrial mammals which occur on the island: the Santa Cruz Island fox (Urocyon littoralis santacruzae), the spotted skunk (Spilogale gracilis amphialus), the deer mouse (Peromyscus maniculatus santacruzae), and the western harvest mouse (Reithrodontomys megalotis santacruzae).

There are 10 birds which are Channel Island subspecies or races. They include: Allen's hummingbird, western flycatcher, horned lark, Santa Cruz Island jay, Bewick's wren, loggerhead shrike, orange-crowned warbler, house finch, rufous-sided towhee and the Catalina quail (introduced). There are many other land and marine birds which make their home on the island.

Due to the large size, and topographic and geologic complexity of Santa Cruz Island, this island supports a wide variety of plant communities. Coastal strand, coastal bluffs, valley and foothill grasses, coastal sage scrub, chaparral, island and oak woodlands, pine forests, southern riparian woodlands, and marsh communities are all present. Introduced cultivated plants occur as well.

There are over 650 different plants on Santa Cruz Island, including both native and introduced species. Forty-two of these plants are endemic to the Channel Islands and 9 are endemic to Santa Cruz Island in particular.

Physiography and Geology

Santa Cruz Island is the most topographically diverse of the Southern California Islands. It is rough and mountainous with deep canyons, and large areas of flat land are limited. Much of the northern shore is bold and rugged, with cliffs dropping to the sea and intersperses with small pocket beaches at the mouths of canyons. Longer stretches of beach are found along the western and southern shores. A large central valley is nestled between two mountain ranges for much of the island's length. Access into this valley is through a narrow, winding, stream filled canyon, three miles long. Picacho Diablo, at 2434 feet in elevation, is the highest point. Several other peaks surpass the 2000 foot mark on the island's north side.

The entire island has a Mediterranean climate. Cool, rainy winters and warm, dry summers. Due to the island's large size and varied topography, a number of microclimates exist. The coastal areas are mild throughout the year. Temperatures rarely rise above 85 degrees or below 35 degrees. However, the central valley may reach over 100 degrees or drop to 20 degrees in the winter.

The geology of Santa Cruz Island varies greatly. The oldest rocks are schists and other metamorphosed sedimentary rocks of pre-Cretaceous period, intruded by Cretaceous and Jurassic quartz diorites. These are found on the island's south side. The northern side of the island contains primarily Miocene volcanic rocks. Limited Pleistocene deposits are particularly well developed at Potato Harbor and on the island's east end.