Chapter V. ESNERR Goal #3
Chaparral is perhaps California's most emblematic vegetation type, forming broad expanses across coastal and inland foothills and constituting about five percent of the state's land cover (Hanes 1988). Ironically, maritime chaparral, a manzanita-dominated association found only in relatively small patches near the coast, is one of our most uncommon and highly threatened vegetation communities. Significant stands of maritime chaparral remain in the Burton Mesa region of Santa Barbara County, near Morro Bay in San Luis Obispo County, and in the Monterey Bay area at former Fort Ord and on sandhills adjacent to Elkhorn Slough. Maritime chaparral is naturally uncommon due to its unusual habitat requirements: sand or similar extremely well drained and nutrient deficient soils, and within the zone of frequent fog along the immediate coast. Maritime chaparral is protected as environmentally sensitive habitat under the California Coastal Act and under Monterey County's Local Coastal Plan (Monterey 1982). Occurrences are mapped as a rare natural community by the California Department of Fish and Game in the California Natural Diversity Database (CNDDB).
Conservation biologist’s understanding of maritime chaparral and its associated rare plants is largely due to the pioneering work of Jim Griffin in the 1970s (Griffin 1978). Maritime chaparral stands are dominated by manzanita shrubs, typically a member of the burl-forming woollyleaf manzanita group in association with one or more of 30 rare non-burl-forming manzanita species that are endemic to restricted regions along the coast. In the Elkhorn Slough watershed, locally endemic Pajaro manzanita shares dominance with another central Monterey Bay area endemic, Hooker's manzanita, and with the more widely distributed brittleleaf manzanita. Several other shrubs, including chamise and toyon, contribute to a dense chaparral canopy. Two federally listed species, threatened Monterey spineflower and endangered Yadon's piperia, are closely associated with Elkhorn Slough's maritime chaparral.
Maritime chaparral patches in the Elkhorn Slough watershed occur within a matrix of coast live oak woodland, coastal sage scrub, and annual grassland as well as agricultural and rural residential development. Maritime chaparral is threatened by removal and fragmentation due to development, encroachment by invasive exotic species such as pampas grass, iceplant, and blue gum eucalyptus, and gradual conversion to other habitat types, particularly live oak woodland.
Figure 5.1: Map of the Elkhorn Slough watershed and maritime chaparral stands.
Preserving Existing Maritime Chaparral
The limited range of maritime chaparral coincides with some of California's most desirable (and expensive) specialty croplands and coastal homesites. Prior to the 1970s, chaparral was generally considered undesirable “scrubland” suitable for clearing and conversion to agricultural use. More recently, maritime chaparral habitat has suffered from removal and fragmentation as a result of residential subdivision. As much as one third of pre-settlement chaparral acreage has been eliminated in north Monterey County, chiefly on lower slopes and plateaus. Much of the region’s remaining maritime chaparral is concentrated along a network of narrow ridgelines.
With certification of the North Monterey County Local Coastal Program (LCP) in 1982, maritime chaparral was afforded protection as environmentally sensitive habitat. The Coastal Act’s environmentally sensitive habitat policies specify that:
Environmentally sensitive habitat areas shall be protected against any significant disruption of habitat values, and only uses dependent on those resources shall be allowed within those areas.
However, the specific policy enacted in the North Monterey County LCP is somewhat less restrictive:
Maritime chaparral is an uncommon, highly localized and variable plant community that has been reduced in North County by residential and agricultural development. Further conversion of maritime chaparral habitat to agricultural uses is highly discouraged. Where new residential development is proposed in chaparral areas, it shall be sited and designed to protect the maximum amount of maritime chaparral. All chaparral on land exceeding 25 percent slope should be left undisturbed to prevent potential erosion impacts as well as to protect the habitat itself.
A stronger LCP policy applies specifically to the 1200 acre Long Valley subwatershed immediately adjacent to Elkhorn Slough National Estuarine Research Reserve (Elkhorn Slough NERR):
Preservation of both the natural habitat and watershed shall be of the utmost priority. Maritime Chaparral and stands of Monterey Pine, Coast Live Oak, Madrone, and Manzanita shall be protected to the maximum extent feasible.
In 1999 ESF in partnership with The Nature Conservancy adopted an Elkhorn Slough Watershed Conservation Plan, which was subsequently endorsed by the California Coastal Conservancy and the California Coastal Commission. A key goal of the plan, which ESF is actively implementing, is to "permanently protect the watershed's best stands of connected maritime chaparral" through land ownership or acquisition of conservation easements.
Today, approximately 2800 acres of maritime chaparral remain in north Monterey County (Figure 5.1). Of this, 1700 acres (61%) are within the boundaries of the Elkhorn Slough watershed. Of the watershed’s maritime chaparral, 350 acres (21%) are within conservation lands protected by ESF and The Nature Conservancy and 160 acres (9%) are within Manzanita County Park. The remaining 1190 acres (70%) are in either developed or as yet undeveloped parcels on privately owned land.
The key to preserving remaining maritime chaparral is developing a network of watershed residents, educators, land managers, land-use decision makers, and scientists who are familiar with chaparral ecology and with policies and practices designed to protect and restore the habitat. This understanding will need to be developed in the visitor center and the classroom, in the laboratory and greenhouse, in the homes and gardens of watershed residents, and in the wild.
Reducing Loss of Maritime Chaparral Due to Habitat Conversion
Dense chaparral covered much of California's central coast uplands at the end of the nineteenth century (Cooper 1922). During the decades since, annual grasslands, scrub, and live oak woodlands have gradually invaded or replaced many of these chaparral stands, although exact acreages and the underlying causes are not well understood.
Chaparral species exhibit a variety of adaptations to natural disturbance, including burls that resprout and refractory seeds that germinate in the aftermath of fire. Under a moderate fire return cycle, burned chaparral will be replaced by essentially the same mix of species. If fire cycles are frequent, a sufficient seed bank of chaparral shrubs may not accumulate and early successional species such as California lilac, coyote brush, or black sage will be favored (Davis et al. 1988). Too frequent fire or intense grazing pressure can lead to habitat type conversion, permanently replacing chaparral with coastal scrub vegetation or even annual grasslands (Odion and Tyler 2002; Keeley 2005). Conversely, infrequent fire return intervals can alter chaparral species composition by favoring crown sprouting species including toyon and coast live oak (Keeley 1992). Numerous studies throughout the central coast region have demonstrated that gradual conversion from maritime chaparral to coast live oak woodland is occurring in the long absence of fire (e.g. Wells 1962; Davis 1972; Griffin 1978; Callaway and Davis 1993; Mensing 1998).
There is considerable controversy over what constitutes a "moderate" or historic fire cycle on the cool and foggy central California coast where rates of lightning-caused ignition are among the lowest in California (Greenlee and Langenheim 1990). Similarly, we lack a clear historic baseline due to disagreements over the relative contributions of grazing by prehistoric herbivores, Native American burning practices, European cattle ranching, and more recent fire suppression practices on the trajectory of habitat type conversion from shrublands to grassland or woodland. The majority of maritime chaparral stands in the Elkhorn Slough watershed have not burned for at least 75 years (Davis 1972). As a result, the density and height of the chaparral shrub layer have increased dramatically and the species composition has shifted from a mix of successional stages to overwhelming dominance by a few long-lived species. At the same time, the size of individual chaparral patches has decreased as oak woodlands gradually invade their perimeters. Within the chaparral canopy, recruitment by new chaparral shrubs is extremely uncommon, while seedlings and saplings of coast live oak are increasingly abundant (Van Dyke et al. 2001).
Three decades ago, gaps in the chaparral canopy were widespread, providing sites for the establishment of shrub seedlings and supporting a diversity of herbs and subshrubs including rare species such as Eastwood's ericameria, Gairdner's yampah, federally threatened Monterey spineflower, and federally endangered Yadon's piperia. Today, gaps are uncommon, resulting in significantly reduced species diversity (Van Dyke et al. 2001).
Even as maritime chaparral is protected from development, type conversion remains an ongoing threat to the habitat. The introduction of prescribed burning and other management practices may be needed in the coming years to minimize the conversion of maritime chaparral to other habitat types and to prevent the loss of rare and endemic species. In preparation, we will initiate a program of applied habitat restoration science, sensitive species recovery planning, and community and decision-maker education.