Biota
There is little ecological diversity on San Nicolas Island. The island was heavily grazed by sheep until they were removed in 1943. Overgrazing and erosion have removed much of the topsoil from the island. Despite the degradation, three endemic plants are found on the island: Astragalus traskiae, Eriogonum grande subspecies tamorum, and Lomatium insulare.
The dominant plant community on the island is coastal bluff scrubland, with giant coreopsis, Coreopsis gigantea and coyote brush, Baccharis pilularis the most visible components. The few trees present today, including California fan palms, Washingtonia filifera, were introduced in modern times. However, early written accounts and the remains of ancient plants in the form of calcareous root casts indicate that, prior to 1860, brush covered a portion of the island.
There are only three species of endemic land vertebrates on the island; the island night lizard, Xantusia riversiana, deer mouse, Peromyscus maniculatus exterus, and island fox, Urocyon littoralis dickeyi. Two other reptiles, the common side-blotched lizard, Uta stansburiana, and the southern alligator lizard Elgaria multicarinatus, were at one time thought to be endemic, but an analysis of mitochondrial DNA indicates that both species were most likely introduced in recent times.
Large numbers of birds can be found on San Nicolas Island. Two species are of particular ecological concern: the western gull, Larus occidentalis, and Brandt's cormorant, Phalacrocorax penicillatus, both of which are threatened by feral cats and island foxes.
The common housecat was one of the greatest threats to the island's wildlife until they were eradicated from the island. The cats killed cormorants, gulls, and the island night lizard. The Navy removed the cats in order to protect the birds' nesting areas. The cats arrived on the island before 1952, probably brought by navy officers that worked there. Many cats have been relocated to a specially prepared habitat in Ramona, in San Diego County, where they can live indefinitely. It is believed that there were no cats left by June 2010, but the weren't officially declared eradicated until 2012. Eradication efforts took 18 months and cost $3 million dollars.
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