California’s Pacific coastline has created a unique evolutionary arena for plants adapted to its salty, abrasive conditions. Regions which are not occupied by coastal prairie grasslands, Redwood trees, or mixed evergreen forests are dominated by this iconic shrub community. Chaparral often comes to mind when associating shrubs with California. Although chaparral dominates a significant range of territory both inland and coastal, an additional shrub community is found in our State, and it is distinct from any other; California’s coastal scrub.
Stretching from southern Oregon to the Mexican border, coastal scrub is intermixed with strands of chaparral. Chaparral’s hard, sclerophyllous leaves and evergreen habit distinguishes itself from the distinctive coastal species. These coastal species are divided between the northern and southern regions based on key differences in morphology and species diversity. Southern Coastal Scrub embodies a high degree of species diversity where plants are commonly drought deciduous and produce soft leaves that emit strong aromatic compounds. Both northern and southern species overlap in Monterey County as their boundaries fade between the two. Species of the Northern Coastal Scrub, strictly found north of San Francisco, are not drought deciduous like their southern counterpart. This phenomena can be attributed to high levels of coastal fog that provide year round moisture in addition to winter rains. Floristically, northern coastal scrub is an assemblage of varying chaparral species and plants endemic to Northern California’s coastline. A distinction between the two communities is subtle and is often not distinguishable as a shifting mosaic between the two is constantly occurring.
Fig A: a commonly observed coastal scrub/chaparral mosaic along the Pacific coastline
The Pacific coastline, in combination with California’s Mediterranean climate, has selected for plants that thrive in harsh conditions. It is a prime example of evolution at work, resulting in a significant degree variation among members of plant communities occupying our coastline. Unfortunately, these biodiverse regions are threatened by urbanization and poor fire management strategies. Current distributions of conservation areas do not support suitable habitat for species of conservation concern. Regions that are host to source populations of Southern Coastal Scrub are threatened by development, habitat destruction, and invasive species. The source patches are of high interest in conservation management and deserve public consideration. Appreciation of these resources is a crucial step to widespread support for preservation of these natural systems.
Fig B: Lupinus albifrons glowing in the coastal California Sunshine
Common ancestor: the species from which a subsequent speciation event took place. An ancestral species shared by 2 or more contemporary species
Diversity: total amount and abundance of species in a collection of individuals.
Drought deciduous: losing leaves in response to drought.
Endemic: a species unique to a specific geographic location.
Evergreen: retaining leaves year round.
Mediterranean climate: hot and dry summers contrasted by wet winters.
Sclerophyllous: tough, sometimes waxy, leaves with a high carbon to nitrogen ratio.
Species on Display:
- Peter Raven, Ray Evert, and Susan Eichhorn. Biology of Plants. Sixth. New York: W.H. Freeman and Company, 1999. Print.
- Campbell, Neil, Jane Reece, et al. Biology. 8th. San Francisco: Pearson Education, 2008. Print.
-Calflora: Information on California plants for education, research and conservation.
[web application]. 2008. Berkeley, California: The Calflora Database [a non-profit organization].
Available: http://www.calflora.org/ (Accessed: Oct 20, 2008).
-All photographs: Creative Commons Attribution