Ecological Restoration of Coastal Sage Scrub and Its Potential Role in Habitat Conservation Plans

Extensive acreage loss of coastal sage scrub (CSS), isolation of surviving stands, and the federal listing of several animal species with obligate relationships to this plant community, particularly the threatened California gnatcatcher (Polioptila californica), have led to attempts to create CSS to mitigate habitat lost to urban development and other causes. Many of these creations lie within habitat conservation plan (HCP) sites, and they could play a more prominent role by being repositories for plants taken from a single site having site-specific genetics. Among others, one technique that increases initial resemblance to natural stands uses digitized, to-scale photography, which has been ground-truthed to verify vascular plant associations, which appear as mosaics on a landscape. A combination of placing patches of salvaged, mature canopy plants within larger matrices of imprinted or container plant plots appears to significantly enhance immediate use by CSS obligate bird species, accelerate “spread” or expansion of CSS, and can also introduce many epiphytic taxa that otherwise would be slow or unable to occupy developing CSS creations. Reptile, amphibian, butterfly, and rodent diversity in a salvaged canopy restoration case study at the University of California, Irvine, showed CSS species foraging and inhabiting transplanted canopy patches. Using restoration techniques to expand existing CSS stands has more promise than creating isolated patches, and the creation of canopies resembling CSS mid-fire cycle stands is now common. Gnatcatchers and other birds use restorations for foraging and occasional nesting, and in some cases created stands along “biological corridors” appear to be useful to bird movement. Patches of transplanted sage scrub shrubs along habitat edges appear to break up linear edge effects. There are no data on which long-term survival, succession, or postfire behavior can be predicted for CSS restoration sites, and postfire community changes are not part of either mitigation or restoration planning at present. Long-term planning including burning is needed so that a fire-adapted habitat will develop. Restoration is important in retaining genetic resources, for ameliorating edge effects, as habitat extenders in buffer zones around HCP sites, and by providing areas into which natural stands can expand.