It is not often that we get to celebrate stories of success regarding the recovery of rare California plants. When asked to provide such stories in the past, we often drew a blank and could only think of the few successful rediscoveries of plants that had been presumed extinct in the past decades.
Although tremendously exciting and significant in and of themselves, these are not the stories of recovery of rare plant populations through effective land management and rehabilitation that people were asking about. Today, however, we are happy to report on one such story. It is the successful recovery of most of the native plants of San Clemente Island.
San Clemente Island is one of the eight Channel Islands located off the coast of Southern California. Together they encompass an exceptional flora with many rare and endemic plant species. Of all the Channel Islands, San Clemente Island has a particularly unique flora, hosting 15 plants that are known from nowhere else in the world, and an additional 48 plants that are only known from the Channel Islands as a whole.
This is due, in large part, to its long history of isolation, being one of the Channel Islands that was not completely submerged during sea level rise in the late Pleistocene Era. This isolation, however, also came with great costs in terms of pressures imposed on the island’s flora throughout its recent history.
Feral goats were introduced onto the island at least by the early 19th century, and by 1840 it was said that the goat population was prolific. Feral pigs were also introduced at an unknown date, and by 1877, sheep and cattle were raised on the island for commercial production. The devastation to the flora caused by these herbivores was immense. A number of plants were extirpated from the island, and it is possible that some plants never known to science became extinct before botanists were able to explore it.
Due in part or entirely from this damage, there are currently 61 plants on the island that are included in the CNPS Inventory of Rare, Threatened, and Endangered Plants of California. Over half of them are California Rare Plant Rank (CRPR) 1B taxa, meaning they are rare in California and throughout their entire known range.
In 1934 the U.S. Navy took acquisition of the island, and by 1972 began removing the feral herbivores in response to the threats they posed. By 1991 the feral goats and pigs had been completely eradicated, with a total of over 29,000 goats removed. Several studies were initiated after the removal of feral animals to determine the status of the island’s vegetation. Today the U.S. Navy actively manages San Clemente Island to promote successful recovery of its native vegetation through continued rare plant surveys, revegetation of natives, weed eradication, and erosion control.
A total of 15 CRPR 1B plants from San Clemente Island have been proposed for down-ranking to CRPR 4 (watch list) due to their recovery. Six of these 1B plants are endemic to the island itself, and two of them — the San Clemente Island lotus (Acmispon dendroideus var. traskiae) and San Clemente Island paintbrush (Castilleja grisea) — are additionally being proposed for downlisting from Federally Endangered to Threatened. These downlistings are particularly significant as they were among the very first plants to gain protection under the Environmental Species Act back in the late 1970’s.
The CNPS Rare Plant Program and the California Department of Fish and Wildlife’s Natural Diversity Database (CNDDB) began initiating the status review process for these plants last year, starting with San Clemente Island paintbrush. (For an explanation of the review process, see the CNPS Bulletin, Vol. 42, No. 1, Jan.-Mar. 2012.) While the paintbrush did not qualify for downranking to CRPR 4, its threat rank was changed from 0.2 (moderately threatened) to 0.3 (not very threatened) in order to reflect its recovery and effective management by the U.S. Navy.
Although many of the other proposed plants might not qualify for downranking mostly due to their restricted distributions, they have recovered remarkably in terms of increased numbers of plants and distribution, as well as active recruitment, throughout the island.
The CNPS Rare Plant Program and the CNDDB staff applaud the U.S. Navy for their commitment to environmental stewardship and conservation.