The San Bruno Mountain
Habitat Conservation Plan
of an Ecological Island
Bruno Mountain is a 3600 acre wildlife refuge in a sea of urbanization. At the
summit, the Mountain rises 1314 feet above sea level with a main ridge extending
4 miles long. It is surrounded on all sides by cities: Daly City, Colma, South
San Francisco, and Brisbane. It is home to three rare (two endangered and one
threatened) species of butterflies, and 10 species of rare plants.
factors contributing to the Mountain's high biological diversity are it's variable
topography and microclimates. The main ridge separates the steeper and dryer southeast
slopes from the more gradual and wetter northwest facing slopes. The southeast
side is dominated by native and introduced grassland vegetation, while the northwest
side is comprised of mostly coastal scrub, and riparian scrub/woodland plant communities.
of the Mountain
mountain was occupied by Ohlone Indians up until the European invasion. Evidence
of Ohlone campsites can be found in a few locations on the mountain. In 1774,
early Spanish explorers climbed San Bruno mountain and in the following year the
mountain was named by Bruno Haceta in honor of his patron saint. The mountain
comprised portions of five Mexican land grants, and was used primarily for cattle
grazing. In 1872, with the American occupation of California, the land was acquired
by the Visatacion land company. The land changed hands several more times among
American companies, yet the primary land-use was still cattle grazing. The mountain
remained undeveloped until the 1960's, when it became the subject of various development
1965, a plan to remove approximately 200 million cubic yards from the top of the
mountain was proposed to provide fill for expanding the San Francisco Airport.
This controversial plan triggered the formation of the Committee to Save San Bruno
Mountain which helped defeat the plan. However more development proposals were
In 1975 Visitacion Associates, a
major land holding company, proposed the construction of 8500 residential units
and 2 million sq. ft. of office space on various portions of the Mountain. One
year later, the mission blue butterfly, an animal only found on San Bruno Mountain
and on Twin Peaks in San Francisco, was listed by the United States Fish and Wildlife
Service as an endangered species. The ensuing battle between developers and environmentalists
resulted in San Mateo County parks buying 1100 acres of land from Visitacion,
and Visitacion donating 546 acres to the County park, and 256 acres to the State.
This secured 1,952 acres of open space into public ownership.
was still interest in developing part of the remaining unplanned portions of the
mountain as well as securing more of the mountain for open space and as habitat
for endangered species.
Habitat Conservation Plan (HCP)
presence of the endangered Mission blue butterfly on the portions of the Mountain
still held by Visitacion Associates, and proposed for development, prompted the
formation of a Steering Committee which had the purpose of resolving the endangered
species/development conflict. The Committee was chaired by the County of San Mateo
and had the following members: U.S. Fish and Wildlife Service, California Department
of Fish and Game, Visitacion Associates and associated developers, City of Brisbane,
and the Committee to Save San Bruno Mountain.
1982 the Steering Committee agreed to the preparation of a plan that would allow
limited development of endangered species habitat in exchange for implementation
of a long-term program, funded by development, to protect and enhance the remaining
portions of the Mountain as habitat. In 1983 Congress amended the Endangered Species
Act to allow this "incidental take" of endangered species on private property.
The new regulation was included in the Act under Section 10(a)(1)B), hence the
requirement for a Section 10(a)(1)(B) permit.
the direction of the Steering Committee, TRA Environmental Sciences prepared the San
Bruno Mountain Area Habitat Conservation Plan. The HCP which covers the entire
area of San Bruno Mountain, was adopted in 1983. The first Section 10(a)(1)(B)
permit was issued by the U.S. Fish and Wildlife Service in March of 1983. The
permit is in effect for a period of 30 years. The HCP designates 11% (368) acres
of the Mountain for planned development, and 81% (2752 acres) for conserved habitat.
The remaining 8% (260 acres) was designed unplanned and is subject to further
The HCP will result in the loss of
up to 14% of the habitat of the Mission blue butterfly and 8% of the habitat of
the Callipe silverspot. As mitigation for this loss, the HCP requires the transfer
of 800 acres of previously privately owned land to the County of San Mateo, and
the generation of a permanent funding source to manage the habitat of the Mountain
Since the HCP was passed in 1983,
actual development of the Mountain has been consistent with what was set forth
in the HCP. As of May 2001, 295 acres of land are either under construction or
completed. Some 320 acres are still designated as unplanned. Parks and Dedicated
Lands make up 2600 acres.
Wildlife and Endangered Species
Mountain supports many common wildlife species including gray fox, , black-tailed
jackrabbit, brush rabbit, raccoon, striped skunk, as well as several bird species
including red-tailed hawks, northern harriers, and great horned owls.
Mission Blue Butterfly 72K photo
addition to the mission blue butterfly, (Plebejus icarioides missionensis)
the mountain is host to the endangered San Bruno elfin butterfly (Incisalia
mossi bayensis), and the threatened callippe silverspot butterfly (Speyeria
callippe callippe). All three butterflies will
take nectar from a variety of plants, but the larvae are specific to the host
plant on which they feed.
Mission blue butterfly larvae only
feed on three species of lupine: Lupinus albifrons, Lupinus variicolor,
and Lupinus formusus. These plants are typically found in open grassland
areas, on rocky slopes, or in recently disturbed areas. Mission blue larvae typically
emerge from diapause (a type of hibernation) in February and begin feeding on
the Lupine leaves. The larvae grow quickly, molting several times, until they
enter their pupal stage. During this stage metamorphosis takes place. The adult
butterfly emerges in late March or early April. During the flight season, between
late March and early June, reproduction takes place. Mating occurs and females
lay their eggs on lupine leaves. The eggs hatch, the tiny larvae feed on the leaves,
and then crawl under the lupine plants where they begin their long diapause.
Picture of California Golden Violet 47K
Callippe silverspot butterfly has a life stage similar to the Mission blue except
that the adults fly later, typically from early May to early August. It's larval
food plant is the California golden violet (Viola peduculata).
San Bruno elfin butterfly larvae feed on the pacific stone crop (Sedum spathufolium).
Unlike the mission blue and callippe, the elfin overwinters in it's pupal stage,
thus in early March metamorphosis occurs and adults emerge and fly until early
April. Larvae hatch from eggs laid on the sedum, and in May of typical years,
larvae can be found on the tops of the sedum flowering heads.
Native Plants and Exotic Plant Infestations
A total of 659 plant species are
known on the mountain in five different community types: Coastal scrub, Chaparral,
Grassland, Wetland, and Woodland. Different community subtypes exist within these
basic community types. Although eucalyptus forests can be found on the mountain
today, no large trees are native to the mountain. Smaller trees such as the coast
live oak, bay, buckeye, and a variety of willow trees are native to the mountain
and can be found in the moister ravines on the mountain.
plants on the mountain are considered rare or endangered. These are:
rock cress ||Arabis blepharophylla|
imbricata subsp. imbricata|
manzanita ||Arctostaphylos imbricata
manzanita ||Arctostaphylos X pacifica|
wallflower ||Erysimum franciscanum|
flower ||Plagiobothrys chorisianus|
|San Francisco campion ||Silene
verecunda subsp. verecunda|
Over the years, the mountain has
been under assault from exotic plant species invasions. Many of these species
can move in and totally overtake an area, overgrowing and destroying the native
plant community and significantly decreasing the habitat value for many native
wildlife species. The most destructive of these species are gorse, eucalyptus,
and french broom.
Exotic plant species that have
more recently become a problem on the mountain include: fennel, cotoneaster, English
ivy, German ivy, and himalaya blackberry.
Habitat Enhancement and Monitoring
Activities conducted under the HCP every calendar year are
documented annually in a report submitted to the U.S. Fish and Wildlife Service.
Copies of these reports are available from the County of San Mateo. The Annual
Reports contain information on the status of the listed butterfly species, exotic
pest plant control work, and development.
species control efforts have been in action since the inception of the HCP, and
continue today. Funds paid into the HCP by homeowners in the developed areas pay
for exotic plant species removal efforts. Dense, extensive plant infestations
are sprayed with herbicide, while the outlying plants are removed by hand. The
removal of certain hardy exotics, such as gorse, takes about 2-4 years. During
the dieback of the gorse, the native plant community has shown to come back on
it's own. Monitoring the relative populations of the butterflies over time has
shown fluctuations in their numbers, yet these appear to correspond more to weather
fluctuations than changes in habitat quantity or quality.
Removal photo 90K
In the spring and summer of 1995, 63 acres of eucalyptus
trees (Eucalyptus globulus), were clear-cut on the mountain. This was done
to remove barriers between butterfly populations, and provide more habitat area
available for the butterflies. The trees were cut at no cost to the County by
Planned Sierra Resources who sold the logs to paper companies.
Plant Community Restoration
cut areas will be replanted with native coastal scrub and coastal grassland vegetation
over the next 5 years. This year 5 acres will be replanted in the Colma Creek
area of the park. Restoration specialist Paul Kephart and Elkhorn Native Plant
Nursery will be conducting the re-planting.
A Flora of the San Bruno Mountains San
Mateo County California by Elizabeth McClintock, Paul Reeburg, and Walter Knight.
1990. California Native Plant Society.
Bruno Mountain Habitat Conservation Plan, Volumes I and II. 1982. County of San
Bruno Mountain State and County Park Brochure, San Mateo County Parks and Recreation
Mountain Concept Plan, San Mateo County Planning Department.