Lichens, which grow slowly and live for many years, represent an important element of the biodiversity of life on public lands. Lichens are a combination of fungus and alga, and are seen on rocks, trees, and fences throughout the region. They are extremely susceptible to air pollution, and some scientists regard them as an indicator species for air quality and climate change. There are approximately 17,000 species of lichen worldwide, with approximately 1,500 species reported from California.
- In a recent survey, more than 100 species were observed on the Point Loma peninsula, with one-third of the species belonging to the maritime community occuring from Baja California in Mexico to central California and the Channel Islands.
- The Channel Islands support the most diverse lichen flora in California with over four hundred species. More than 300 lichens have been reported from Santa Rosa Island alone.
- Over 200 species have been documented in the Santa Monica Mountains. Several lichen species are considered rare based on herbarium records and field observations.