Santa Cruz Island rock cress (Arabis insularis) is a rare and endangered plant species that is endemic to Santa Cruz Island, which is one of the Channel Islands located off the coast of Southern California. It belongs to the family Brassicaceae and is commonly known as the "Santa Cruz Island wallflower". It is a low-growing perennial herb that is adapted to the harsh and arid island environment.

Description: Santa Cruz Island rock cress grows up to 30 centimeters in height and has a spreading habit. Its leaves are narrow and elongated, and they grow in a rosette at the base of the plant. The flowers are small, white, and grow in clusters at the tips of the branches. The plant blooms from February to April, and it produces fruits that contain seeds.

Habitat and Distribution: Santa Cruz Island rock cress is found only on Santa Cruz Island, which is part of the Channel Islands National Park. It is restricted to rocky outcrops and cliffs in the interior of the island, where it is exposed to strong winds and extreme temperatures. The plant is adapted to the arid and rocky conditions of the island, and it is able to survive in shallow soils and in areas with low water availability.

Conservation Status: Santa Cruz Island rock cress is listed as an endangered species by the US Fish and Wildlife Service, and it is protected under the Endangered Species Act. The plant is threatened by habitat loss, invasive species, and climate change. The island's ecosystem has been greatly impacted by non-native species such as feral pigs, which have destroyed the plant's habitat and compete with it for resources. The National Park Service is actively working to protect and conserve the plant by controlling invasive species, restoring degraded habitats, and monitoring the population size and health of the species.

Ecological and Cultural Importance: Santa Cruz Island rock cress is an important species in the ecology of Santa Cruz Island, where it serves as a food source for insects and provides habitat for small animals. The plant also has cultural significance for the Chumash people, who are indigenous to the Channel Islands. The Chumash used the plant for medicinal and ceremonial purposes, and they valued its resilience and adaptability to the island's harsh environment. The conservation of Santa Cruz Island rock cress is important not only for its ecological value but also for its cultural significance and the preservation of the island's unique biodiversity.