We recently submitted to the U.S. Forest Service an official petition to list the Cuesta Ridge thistle (Cirsium occidentale var. lucianum) as a sensitive species in the Los Padres National Forest. Listing of the species would grant it special considerations and protections when the agency proposes projects that may impact individual plants and populations.
The plant is a recognized variety of the common and widespread cobwebby thistle that is found throughout the national forest. Unlike the cobwebby thistle, however, the Cuesta Ridge thistle is found in only one place on Earth: along Cuesta Ridge in the Santa Lucia Mountains near San Luis Obispo.
The ultimate aim of a sensitive determination is to prevent a species from becoming federally listed as threatened or endangered as well as keeping it from becoming locally extinct on national forest land. This is especially important when most of the known populations occur only on national forest land, which is the case for the Cuesta Ridge thistle.
Cuesta Ridge is the most popular recreation area in the Santa Lucia Ranger District. In fact, the Forest Service recently closed access to West Cuesta Ridge due to overuse and fire risk from illegal camping. Despite being home to the Cuesta Ridge Botanical Special Interest Area, the area has experienced an increase in illegal trail-building in recent years as well. All of these issues are putting stress on the Cuesta Ridge thistle, which is limited to the narrow ridgeline corridor.
Unlike the San Luis Obispo fountain thistle, a related species that is also limited to areas nearby, the Cuesta Ridge thistle is not protected under the Endangered Species Act. Despite occurring primarily within the Los Padres National Forest, the plant is not considered a sensitive species by the Forest Service either.
The sensitive species petition is currently being considered by the Forest Service’s regional botanist. There is no specific timeline for when the agency will make a determination, but we expect to receive a decision in 2021.
Special thanks to Jonathan Hart, our former Conservation GIS Intern from the Bren School at UCSB who conducted literature review, consulted with experts, and drafted the petition.
You can learn more about the Cuesta Ridge thistle here.
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