THE DALY CITY DUNES
Remnants of California's ancient coastline
The Daly City Dunes, on the western end of San Bruno Mountain, are the last remnants of an ancient dune system formed 80,000 to 125,000 years ago during the Pleistocene era - when the northern San Francisco Peninsula was an island. These dunes are unique on the peninsula since the San Francisco coastal dunes were formed by a different process and during a much later era.
This inland dune system in Daly City also has a diverse and healthy plant community containing typical dune scrub species, plus rare and endangered California native plants. The San Francisco Lessingia (Lessingia germanorum), on the Federal Endangered Species list since 1997, is found only in two areas on the peninsula: 1) the Presidio, under the care and protection of the Golden Gate National Parks Conservancy; and 2) in the Daly City Dunes.
San Bruno Mountain Watch has surveyed the dune area and GPS-mapped locations containing significant populations of lessingia. The GIS map of the area (click map to enlarge) shows that San Francisco Lessingia is prevalent over much of the threatened dune area.
Though significant portions of the dunes were recently donated to become part of San Bruno Mountain State and County Park, some parcels at the heart of these rare dunes remain privately owned and are currently threatened with development. The recently purchased property is now slated for a school classroom extension, a new ballfield, and up to twenty-five parking spots. This construction would require a large retaining wall and extensive grading. The planned development, involving addition of street access, would fragment the dune area and leave remaining areas vulnerable to more deterioration.
In the upper reaches of the dune area there is another important feature - an Ohlone Indian shellmound. This shellmound has been documented and registered with the State of California. Such sites are considered sacred, and there are laws governing how they are treated. It takes vigilance and public will to assure that the laws are followed, and that these sites are treated with the respect they deserve. Although the Ohlone don't usually like to publicize the locations of these sites, in this case they have agreed to let us inform the public.
For San Bruno Mountain Watch, the reasons to preserve this unique feature of San Bruno Mountain are obvious: they provide a unique link to California's historic coastline; open spaces provide a sense of well-being; and future generations should be able to continue to enjoy the diverse landscapes of San Bruno Mountain, one of the world's biodiversity hotspots. We hope to convince the owners of the threatened parcels of the value of saving this rare treasure. It would be a wonderful legacy gift to the people of Daly City and the Bay Area if they were to work with us to preserve this unique area.
DALY CITY DUNES PLANTS
In spite of numerous assaults from development and invasive plant species in recent decades, this unique remnant of ancient dunes still supports a variety of plants characteristic of an inland dune scrub plant community. The plant diversity is impressive and is dominated by Chamisso Bush Lupine (Lupinus chamissonis), California Goldenbush (Ericameria ericoides), Coast Buckwheat (Eriogonum latifolium),California Phacelia (Phacelia californica), Sandmat (Cardionema ramosissimum), Dune Knotweed(Polygonum paronychia) and Common Deerweed (Lotus scoparius) - to list only a few of the more widely-spread California native dune species.
Other plants of particular interest are the rare San Francisco Spineflower (Chorizanthe cuspidata var. cuspidata), the Sandysoil Suncup (Camissonia stingulosa) and Davy’s Clarkia (Clarkia davyi).
What is incredibly special about the Daly City Dunes, however, is that this habitat supports the only remaining, naturally occurring, population of the rare and endangered San Francisco Lessingia (Lessingia germanorum) outside of the Presidio. In recognition of its rare status, the San Francisco Lessingia was protected as an endangered species under the Federal Endangered Species Act in 1997.
The San Francisco Lessingia, an annual herb in the sunflower family, once occurred throughout San Francisco’s vast dune system. Like many dune plants, it thrives in open sandy areas subject to being disturbed – thus reducing the competition from both invasive species and other natives. But it is not immune to the threats of habitat loss due to development, or the many other potential dangers resulting from human activities and their ecological consequences.
Top Invasives: fox-tail fescue (Vulpia myuros); ripgut brome (Bromus diandrus); iceplant (Carpobrotus edulis); crown daisy (Glebionis coronaria); Bermuda buttercup (Oxalis pes-caprae); hairy catsear (Hypochaeris radicata); smooth catsear (Hypochaeris glabra); redstemmed filaree (Erodium cicutarium); wild oat (Avena fatua); rabbitsfoot grass (Polypogon monspeliensis); bur clover (Medicago polymorpha); sweet alyssum (Lobularia maritima)
Most people who live in the San Francisco Bay Area are familiar with the coastal dunes along the Great Highway at Ocean Beach and Fort Funston. They may even be aware of the dunes in the Presidio and Baker Beach at the northernmost part of the peninsula. What you see there are surviving fragments of a once vast coastal dune system on the northern San Francisco Peninsula – now covered with homes and lost forever to development decades ago. These Holocene Sand Dunes were most likely formed from sand brought down from the Sierra by the Sacramento/San Joaquin River system, forming a broad coastal plain. However, these coastal dunes are youngsters - formed during a period a mere 18,000 and 5,000 years ago.
On the western end of San Bruno Mountain you can find much more ancient dunes. The Daly City Dunes in Hillside Park, on the lower slopes of Reservoir Hill, loom above the houses on Bonnie Street. These are the remaining remnants of truly ancient dunes that were formed from 80,000 to 125,000 years ago as part of the Pleistocene Colma Formation. This deposition occurred during an interglacial period when the sea level was higher than today. This higher water level from melted glaciers made the northern San Francisco Peninsula an island - separated from the southern peninsula by a narrow stretch of water connecting the ocean to the bay.
When ocean waters reached the base of an ancient San Bruno Mountain, the deposit of material from several environments, over thousands of years, created the sands of the Colma Formation. Contributions from shallow tidal lagoons and silt from valley slopes gave this sand more soil-like properties and its characteristic iron-stained brownish coloring, contrasted to the gray sands of the coastal dunes.
THE THREAT OF DEVELOPMENT
The map below (click to enlarge) shows that most of the remaining San Bruno Mountain dune system in Daly City is publicly owned (in yellow text). The area outlined in red remains in private hands. San Bruno Mountain Watch would like to see all privately owned parcels transferred to public ownership so that this rare geologic and botanical resource can be preserved intact rather than fragmented. Naturally, we believe the present owners should be adequately compensated.
This map shows the potential school expansion site and its location relative to what is now a diverse dune plant community containing rare and endangered plants. The area in blue has been donated to San Bruno Mountain State and County Park. The light green areas show the location of the significant population of the federally endangered San Francisco Lessingia (Lessingia germanorum). In addition, an Ohlone shellmound exists on the dunes where classrooms, parking and an access road are planned.
The large amount of grading, infrastructure installation, retaining wall, ballfield and classroom construction will disturb this fragile area. Any major construction on these dunes, whether they directly destroy endangered species or not, will be detrimental to San Francisco Lessingia and the dune community that rely on the wind swept shifting sands. Development will also further fragment this habitat and fragmentation is a common cause of species extinction.
In addition, the planned development will double the size of the school causing possible traffic congestion.
The Potential for Open Space
If this land were to be preserved, it would create a continuous stretch of dunes between a city park and a county park, and within walking distance of seven schools and the Teglia Community Center. Daly City citizens could enjoy uninterrupted trails with interpretive information that would shed light on the unique geological, botanical and human heritage of this area. Our vision is to have surrounding schools, and community, involved in the restoration and education of a unique resource. How many neighborhoods have endangered plants in their backyards?
Please email us at email@example.com if you would like to be notified of public hearings and be involved in our efforts to save this important piece of San Bruno Mountain.