Coastal Sage Scrub

Mature coastal sage scrub habitat is made up of predominantly native shrubs interspersed with forbs and grasses. Healthy, uninvaded coastal sage scrub with a fire return interval of approximately 30 years will reach peak diversity two years after a fire. Because it can be lost to a range of human-driven threats—from development and invasive species introductions to changes in fire frequency and climate—it functions as an important indicator of ecosystem health. Extensive disturbance can result in the conversion of coastal sage scrub to invaded grassland and an associated loss of native vegetation and habitat for many of the area’s important species.

Since 2007, long-term monitoring on Reserve lands has tracked the metrics used in this assessment: native shrub cover, fire return interval, invasive grass and forb species cover, and native species richness. Results show the condition of the Central Study Area as caution for native shrub cover and low invasive forb cover, and of significant concern for fire frequency and low invasive grass cover. However, native species richness is in good condition. The Coastal Study Area is generally in good condition, except for native species richness, the condition for which is caution. Both areas show a mix of unchanging and declining trends, with an overall high level of confidence in this assessment in the Central Study Area and moderate confidence for the Coastal Study Area.

It will be important to continue monitoring this indicator to track the health of these important habitats. Conservation and management efforts would benefit from more information about specific disturbances or climate changes that could lead to its conversion to invaded annual grassland. Likewise, to support restoration efforts, it would be helpful to identify native species that can out-compete invasives during their establishment phase.