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Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
THE REMNANT COASTAL DUNES OF SOUTHERN CALIFORNIA
K
EVIN
B.
C
LARK
Clark Biological Services, 7558 Northrup Drive, San Diego, California 92126 (kevin.b.clark@sbcglobal.net)
ABSTRACT
Coastal dune systems were once extensive in southern California. Pervasive human modification of easily disturbed and highly
desirable coastal strand areas have left only small remnants. In order to assess the remaining extent of coastal dunes in the region,
I have repeatedly surveyed the remaining coastal dune vegetation from Santa Monica, Los Angeles County, to the U.S.-Mexico
border. Species characteristic of California coastal dunes include Abronia maritima, Ambrosia chamissonis, and Camissonia
cheiranthifolia subsp. suffruticosa. The introduced Cakile maritima and Carpobrotus edulis are ubiquitous. Less common
perennials include Abronia umbellata, Atriplex leucophylla, Calystegia soldanella, and Distichlis spicata. Annuals tend to be
more easily extirpated and are found less frequently, including Lotus nuttallianus and Nemacaulis denudata var. denudata. A
small dune system in central Orange County contained a population of Cryptantha leiocarpa, previously undocumented south of
Point Conception. The principal threats to the remaining dunes include continuing coastal development and especially the
extensive beach raking by parks and recreation departments that removes the vegetation from many miles of coastal strand
annually.
Key words: beach raking, coastal dunes, coastal strand, endangered species, rare plants, restoration.
INTRODUCTION
Coastal dune systems were once extensive in
southern California. The El Segundo dunes between
Venice and the Palos Verdes peninsula once covered
nearly 25,000 acres (100 km
2
) (Cooper 1967). Just to
the south, a massive dune and marsh complex
connected the mouths of the Los Angeles and San
Gabriel Rivers down to present-day Huntington
Beach, a distance of over 15 miles (24 km). Most of
the shoreline of southern San Diego County from La
Jolla to the U.S./Mexico border was also extensive
coastal dune and marsh. These coastal areas have
nearly all been developed by now, but there are
surviving examples of what the coastal flora used to
look like. What’s more, there are numerous beaches
in public ownership that have the potential to support
dune communities with only minimal changes in
management and use.
Coastal dune systems are typically divided into
active foredunes, often thinly vegetated, and
subjected to constant wind, sun, and blowing sand;
backdunes, which on the west coast are protected
from the afternoon sun and generally support higher
and denser vegetation; lee or deflation plains, which
are the more stabilized sandy flats behind the active
systems and often support the highest plant diversity;
and dune hollows or pools, which can vary from
relatively mesic to supporting standing water year-
round (Cooper 1967). Each of these micro-habitats
support their own specialized species (Pickart and
Sawyer 1998). In southern California, over ten
sensitive plant taxa are primarily restricted to coastal
dune habitats (CNPS 2009).
With this kind of diversity it is surprising that so
little attention is paid to coastal dunes. Part of the
reason is that so much has been destroyed that there
are few examples of what dune systems used to look
like. However, recent surveys have shown that many
remnants still remain, and with most of them in
public ownership, there is great potential for restoring
extensive areas to their former state. An increased
awareness among beach managers and the general
public about the value of this endangered system is
needed to reverse the long-term decline of coastal
dunes.
METHODS
From 2000 to 2009, coastal strands and dunes
containing native vegetation were identified and
repeatedly surveyed floristically. Those that
supported only exotics, principally Carpobrotus
edulis (L.) N.E.Br., were not included. Some of the
remnant dune systems were identified during survey
work for western snowy plovers (Charadrius
Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
21
alexandrinus nivosus) while I was Southern
California Recovery Coordinator for the species with
the U.S. Fish and Wildlife Service (USFWS) in
Carlsbad, California. Efforts were made to voucher
species where access and permissions were provided,
and this work is ongoing. A small number of
vouchers are deposited at Rancho Santa Ana Botanic
Gardens (RSA-POM). The following results
summarize this work and synthesize discoveries by
others at coastal dunes within the region.
RESULTS AND DISCUSSION
Coastal dune vegetation was found to persist at
twenty-five separate coastal sites (Table 1). Most
sites have some degree of invasion of exotic species,
primarily Carpobrotus edulis and Cakile maritima
Scop. Many sites also support protected birds or
Table 1. Summary of dunes, acreage, floristics, and notes. Sites arranged from north to south. Plant species richness: 1 = 1–5
species; 2 = 6–10 species; 3 = 10+ species. Exotics: percent cover of exotic species, principally Carpobrotus edulis, over dune
remnant.
Site Acres Plant richness Exotics
Notes
—Notable species
Venice Beach 7 1 Low Least tern preserve, Abronia maritima
Ballona dune 10 2 Med Formerly Potentilla multijuga
LAX-El Segundo 300 3 Med
Pholisma arenarium
, Mucronea californica, Camissonia lewisii,
El Segundo blue butterfly
Dockweiler SB 4 2 Med Calystegia soldanella
Chevron preserve 1 3 Low El Segundo blue butterfly
Malaga 57 3 High
Pholisma arenarium
, Palos Verdes blue butterfly, El Segundo
fly,
Erysimum insulare
subsp.
suffrutescens
Seal Beach 3 2 Med Calystegia soldanella, Abronia umbellata
Surfside/SBNWS 19 2 Low Calystegia soldanella, Atriplex leucophylla, Abronia maritima
Bolsa Chica 2 2 Low
Nemacaulis denudata
var. denudata, Atriplex leucophylla,
Huntington SB 3 1 High
Abronia maritima
, Calystegia soldanella
Santa Ana River 12 2 Low
Nemacaulis denud
ata var. denudata, Abronia maritima,
California least terns
Balboa Pier 20 2 Low Calystegia soldanella, Nemacaulis denudata var. denudata,
Cryptantha leiocarpa
San Onofre SB 8 2 Low Largest Atriplex leucophylla population, Abronia maritima
Santa Margarita 50 3 Low
Lotus nuttallianus
, Nemacaulis denudata var. denudata,
Phacelia stellaris
Batiquitos 1 1 Low
Nemacaulis denudata
var. denudata, Abronia umbellata
San Elijo 2 2 Low
Nemacaulis denudata
var. denudata, Abronia umbellata
San Dieguito 8 2 Low
At
riplex leucophylla, Abronia maritima
Penasquitos 1 3 Low
Nemacaulis denudata
var. denudata, Heterotheca sessiliflora
subsp. sessiliflora, Lotus nuttallianus
Fiesta Island 3 3 High
Nemacaulis denudata
var. denudata, Lotus nuttallianus,
Abronia maritima
,
San Diego River 12 1 Low
Lotus nuttallianus
, Abronia maritima
North Island
31 2 High
Phacelia stellaris
, burrowing owls, snowy plovers
Coronado 20 3 High
Nemacaulis denudata
var. denudata, Abronia maritima, mesic
dune hollows
Silver Strand SB 31 3 Low
Nemacaulis
, Lotus nuttallianus, Phacelia stellaris, Atriplex
leucophylla, Heterotheca sessiliflora, dune hollows, snowy
plovers
NRRF
44 2 High Cordylanthus maritimus var. maritimus, dune hollows, San
Diego fairy shrimp
Border Field SP 73 2 Low
Nemacaulis
, Phacelia stellaris, Lotus nuttallianus, Frankenia
palmeri, California legless lizard
[SB = State Beach, SBNWS = Seal Beach Naval Weapons Station, SP = State Park]
Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
22
invertebrates, which was often the primary reason
that the dune sites are still extant (Table 1). Several
sites are extremely limited in area, with one acre or
less of the site supporting native vegetation (Table 1).
Nineteen sites were surveyed for floristics (Table
2). The most frequently encountered native species
include Camissonia cheiranthifolia (Hornem. ex
Spreng.) Raim subsp. suffruticosa (S.Watson)
P.H.Raven, Ambrosia chamissonis (Less.) Greene,
and Abronia maritima S.Watson. Several species
show distinct distributions within the study area.
Calystegia soldanella (L.) R.Br. is frequently
encountered in the northern dune systems in Los
Angeles and Orange counties, while it is rarely found
in San Diego County. Both Lotus nuttallianus Greene
and Nemacaulis denudata Nutt. var. denudata show a
southerly distribution, with Lotus not being found
north of San Diego County, while the distribution of
Nemacaulis ends in central Orange County. Rare
species found at few sites include Atriplex
leucophylla (Moq.) D.Dietr., Phacelia stellaris
Brand, and Heterotheca sessiliflora (Nutt.) Shinners
subsp. sessiliflora.
At the high tide line, the first terrestrial plant to
make an appearance is Atriplex leucophylla. This
species is extremely salt tolerant, being regularly
overwashed by the highest tides. It is also one of the
rarest dune species in the region, being one of the
first to succumb to the beach-raking activities.
Because it does not occur much beyond the
beginning of the foredune, it is typically completely
extirpated from beaches that are mechanically
groomed. Recent surveys have located only five
occurrences in the study area, each with fewer than
100 individuals (Table 2). Farther up the beach,
Abronia maritima appears, and the beginning of dune
topography begins to be noticed. Abronia maritima
accretes blowing sand, and as a mound of sand
begins to form over this perennial, the plant
continually grows out of the top. Ambrosia
chamissonis is another mat-forming perennial that
occurs in the foredune. Other typical foredune
species include Calystegia soldanella, Camissonia
cheiranthifolia subsp. suffruticosa, and the
introduced Cakile maritima. The backdunes typically
support many of the preceding species, as well as
Nemacaulis denudata var. denudata, Distichlis
spicata (L.) Greene, Abronia umbellata Lam., and
Heliotropium curassavicum L. The flatter deflation
plain behind the dunes proper is where the floristic
diversity is at its peak. Species found here include
many of the preceding species plus specialists such as
Camissonia lewisii Raven, Phacelia stellaris, and
Heterotheca sessiliflora subsp. sessiliflora.
Because of the increased soil moisture, dune
hollows support a variety of taxa more typical of
wetland environments such as Antirrhinum
nuttallianum Benth., Carex spp., Distichlis spicata,
Frankenia salina (Molina) I.M.Johnst., Heliotropium
curassavicum, Jaumea carnosa (Less.) A.Gray,
Juncus acutus L., and even Salix spp. There are very
few remaining dune hollows left in southern
California, with Silver Strand State Beach and the
Naval Radio Receiving Facility to its south
containing the majority of those remaining. Several
species once found in dune hollows in the region
have been extirpated, including Astragalus tener
A.Gray var. titi (Eastw.) Barneby, which is now
relegated to one declining population in Monterey
(USFWS 2004); Astragalus pycnostachyus A.Gray
var. lanosissimus (Rydb.) Munz & McBurney, long
thought extinct until rediscovered in Oxnard; and
Potentilla multijuga Lehm., which was restricted to
the El Segundo dunes near Ballona and hasn’t been
observed in over a century (Ertter 1993).
Coastal dunes in Southern California have received
relatively scant attention by naturalists in recent years
as attention has shifted to declining coastal sage
scrub and other habitats. The lack of recent survey
work in coastal dunes is illustrated by the discovery
of a population of Cryptantha leiocarpa (Fisch. &
C.A.Mey.) Greene on a small pocket of dunes near
the Balboa Pier in central Orange County (Clark
2006). This species had previously not been found
south of Point Conception, but is common at this site
(Fig. 1).
Fig. 1. Cryptantha leiocarpa from Balboa Pier
dunes. Photo by Kevin B. Clark.
Besides the diversity of flora that exists in coastal
dunes, there is a wealth of specialized animals that
have adapted to the unique hardships posed in the
dune community. Birds such as horned larks
Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
23
Table 2. Selected species distributions.
Camissonia cheiranthifolia
subsp
. suffruticosa
Cakile maritima
Ambrosia chamissonis
Abronia umbellata
Distichlis spicata
Abronia maritima
Heliotropium curassavic
um
Nemacaulis denudata
var
. denudata
Carpobrotus edulis
Heterotheca grandiflora
Nutt.
Calystegia soldanella
Cynodon dactylon
(L.) Pers.
Atriplex leucophylla
Lotus nuttallianus
Phacelia stellaris
Heterotheca sessiliflora
Cryptantha leiocarpa
Venice Beach X X X X
Dockweiler SB
X X X X X X X X X X
Seal Beach
X X X X X X X X X X
Surfside/SBNWS
X X X X X X X X X
Bolsa Chica
X X X X X X X X X
Huntington SB
X X X X X X X
Santa Ana River X X X X X X X X
Balboa Pier
X X X X X X X X X
San Onofre SB
X X X X X X X X X
Santa Margarita
X X X X X X X X X X X X
Batiquitos
X X X X X X X X X
San Elijo
X X X X X X X
San Dieguito X X X X X X X X X X
Penasqu
itos
X X X X X X X X X X X
Fiesta Island
X X X X X X X X X
San Diego River
X X X X X
Coronado
X X X X X X X X X X X
Silver Strand SB
X X X X X X X X X X X X X X X X
Border Field SP X X X X X X X X
Count 19 19 18 15 15 14 12 11 11 10 9 6 5 4 2 2 1
[SB = State Beach, SP = State Park, SBNWS = Seal Beach Naval Weapons Station]
(Eremophila alpestris), burrowing owls (Athene
cunicularia), and the threatened western snowy
plover (Charadrius alexandrinus nivosus) use dune
systems for foraging and nesting. The endangered
California least tern (Sterna antillarum browni) nests
in significant colonies in some dune systems, which
is often the only reason that these dunes haven’t been
cleared. Mammals such as the San Diego black-tailed
jackrabbit (Lepus californicus bennettii) and reptiles
such as the California legless lizard (Anniella
pulchra) and coast horned lizard (Phrynosoma
coronatum blainvillei) spend their entire lives in the
dunes. Rare and little-known insects such as the
globose dune beetle (Coelus globosus) and sandy
beach tiger beetle (Cicindela hirticollis gravida) are
entirely restricted to these dune systems.
KEY REMNANT DUNE SITES
A small number of coastal dunes survive in southern
California that still harbor populations of rare and
endangered species. The El Segundo dune system is a
well known pocket of endemism that has almost been
lost several times in recent history, with houses built
and torn down, and golf course plans proposed and
rescinded (Mattoni 1990). Some of the earliest
ecological studies were performed within this dune
system, with Couch (1914) noting the predominance
of Erysimum insulare Greene subsp. suffrutescens
(Abrams) R.A.Price on the top of the dunes. This
species has long been in decline and is on the CNPS
list (CNPS 2009). Pierce and Pool (1938) noted the
presence of Dithyrea maritima (Davidson ex
Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
24
B.L.Rob.) Davidson on the active portion of the
dune, though this rare mustard now appears to be
extirpated from southern California. Currently the
300-acre dune remnant at the west end of the LAX
airport is in a tenuous stasis with a still uncertain
future. The 300-foot-tall dunes support rare taxa such
as Mucronea californica Benth., Camissonia lewisii,
and Pholisma arenarium Nutt. ex Hook., while
Isocoma menziesii (Hook. & Arn.) G.L.Nesom,
Eriogonum parvifolium Sm., and Lupinus albifrons
Benth. form a dune scrub community on protected lee
slopes (Mattoni 1990). Just east of the main dune
ridge the topography flattens to a sandy plain
supporting one of the last examples of the coastal
prairie community that once covered much of what is
now western Los Angeles (Longcore and Mattoni
1997). The formerly extensive vernal pools and dune
hollows east of the dunes are now only a remnant,
with a few shallow pools persisting on the LAX
airfield, with the endangered Riverside fairy shrimp
(Streptocephalus woottoni) and western spadefoot
toads (Spea hammondii) hanging on as well.
A few miles to the south, Malaga dune represents a
completely unique dune system located on the bluffs
of the Palos Verdes peninsula over 300 feet above the
ocean. These dunes are likely of Pleistocene origin
and represent the southern extension of the
previously more extensive El Segundo dunes (Cooper
1967). This dune contains many rare taxa that have
persisted amongst the surrounding housing
developments, roadways, and golf course. Among the
taxa recorded from this site are Pholisma arenarium,
a root parasite found on perennial shrubs such as
Ericameria and Eriogonum spp., and Erysimum
insulare subsp. suffrutescens. Other notable species
include the endangered Palos Verdes blue butterfly
(Glaucopsyche lygdamus palosverdensis) and the El
Segundo flower-loving fly (Raphiomidas terminatus
terminatus), until recently thought to be extinct and a
close relative of the endangered Delhi Sands flower-
loving fly (Raphiomidas terminatus abdominalis)
(George and Mattoni 2006). Unfortunately, this 57-
acre site is overrun with exotic plants such as
Eucalyptus, Acacia, Bromus diandrus Roth, and
many others. However, as it is owned by the city of
Palos Verdes Estates adjacent to the Palos Verdes
Golf Club, a restoration project could bring this dune
system back.
The Santa Margarita dunes, located on the Camp
Pendleton Marine Corps Base in northern San Diego
County, are perhaps less well known because of the
limited access. However, these dunes represent a
diverse flora that is located on a natural estuary at the
mouth of the largest undammed river in southern
California. These dunes contain one of a few known
populations of Phacelia stellaris and healthy
populations of the rare Lotus nuttallianus, here at its
northern distributional limit. The dunes show a
natural gradation between sparse foredunes to
saltmarsh vegetation at the estuary to dense vegetated
backdunes at the base of the low bluffs. Portions of
this dune system also support one of the largest
California least tern colonies with over 1000 pairs
nesting there.
At the southwest corner of San Diego Bay lies the
U.S. Naval Radio Receiving Facility. This site is the
last southern California site with vernal swales and
pools backing the dune system. Comparisons of
historic maps with current aerial photography (Fig.
2–3) show the persistence of the dune swales over
extended periods. These vernal pools are occupied by
the San Diego fairy shrimp (Branchinecta
sandiegonensis), an endangered species. Here the
endangered saltmarsh bird’s beak (Cordylanthus
maritimus Nutt. ex Benth. subsp. maritimus) occurs
in brackish pools behind the dunes, the only known
site that this plant occurs outside of tidal salt marsh.
Unfortunately, the majority of the dunes themselves
have been taken over by Carpobrotus mats that have
swamped most native taxa. These dunes continue for
about 1.5 miles of coastline before they meet up with
the south end of Silver Strand State Beach, now
restored and managed for endangered species.
Together, these two sites represent one of the largest
intact dune systems left in southern California.
Border Field State Park and the adjacent Tijuana
Slough National Wildlife Refuge at the southwestern
corner of the U.S. support a dune system similar to
the Santa Margarita dunes in that it occurs on a
natural barrier beach in front of a dynamically
changing estuary and river outlet. Here, the rare
Frankenia palmeri S.Watson creeps up the back of
the dune swales from its comfort zone in the adjacent
saltmarsh and California legless lizards swim through
the sand under mats of Abronia maritima.
CONSERVATION AND RESTORATION
Southern California coastal dunes have been in
decline since the construction of Highway 1 in the
early part of the twentieth century. This not only
directly modified and fragmented the dune structure
by generally splitting the foredunes from the
backdunes, but it contributed to coastal access by
vacationers and developers that would create further
changes. As these coastal areas were developed,
increasing public use of beaches led local cities to
begin mechanized beach cleanup operations. These
Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
25
Fig. 2. Detail of 1857 map of San Diego Bay by the U.S. Navy (U.S. Navy 1857). Note the two mesic areas in the sandy flats
to the southwest of the bay. Also note the three pools just behind the dunes. Photo by Kevin B. Clark.
Fig. 3. Current aerial photo of Naval Radio Receiving Facility site. The two mesic areas from the 1857 map (Fig. 2) are clearly
visible east of the circular fenced radio facility. The three pools are also still present east of the dunes south of the radio. One of
these pools supports Cordylanthus maritimus var. maritimus. Image courtesy of Google Earth.
Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
26
rakes and groomers not only pick up the trash, but
scrape away all vegetation, while also flattening the
natural dune topography (Fig. 4). The vast majority
of public beaches in Los Angeles and Orange
counties are now raked on a daily or weekly basis
year round, prohibiting any dune formation or
vegetation to occur.
Dunes in northern Baja California have been
degraded through the years as well, though not to the
extent of those north of the border. The dune system
at El Descanso has been persistently degraded for
years by off-road vehicle traffic. Farther south, the
dunes around La Salina have been lost to marina and
home development. The dunes at El Estero de Punta
Banda are partially protected and a nice example of
coastal dune flora, yet this area is also under threat
from home development and human disturbance. The
dunes near Colonet are under threat from a proposed
port development (Clark et al. 2008) while those at
San Quintín have no permanent protection (S.
Vanderplank, pers. comm.).
Fig. 4. Beach raking in Los Angeles County. Most of the
beaches in Los Angeles and Orange counties are raked on a
weekly basis throughout the year. All vegetation and dune
topography is cleared in these operations. Photo by Kevin
B. Clark.
In some areas of Southern California, local efforts
are succeeding in restoring the native flora and fauna
back to coastal dunes. In between Malaga dune at
Palos Verdes and the El Segundo dunes at LAX lie
several miles of sandy bluffs and slopes that back the
public beaches of southwestern Los Angeles. In the
city of Redondo Beach, a restoration project has
begun on one of these bluffs that was formerly
covered with extensive mats of Carpobrotus.
Undertaken by the Los Angeles Conservation Corps'
SEA Laboratory and The Urban Wildlands Group,
this project has created a thriving native plant
community on over one mile of bluff (Urban
Wildlands Group 2009). Numerous signs educate the
public to the value of native species (Fig. 5). A few
years after the plantings, the project area was
naturally colonized by the endangered El Segundo
blue butterfly (Euphilotes battoides allyni), adding a
new population to the few that remain.
The mouth of the San Diego River has likewise
been adopted by an active group called the Friends of
the San Diego River. A multi-year effort initiated by
the non-profit group Ocean Discovery Institute has
succeeded in removing Carpobrotus and other
invasives and planting native plants (Ocean
Discovery Institute 2009). A few years back over 20
pairs of California least terns colonized the dune
system, some successfully raising a brood of young
despite the presence of an unleashed dog park
adjacent to the area.
Silver Strand State Beach represents a great
example of what coastal beach management could
look like. A heavily used public recreational beach
with RV parking is located on one portion, while to
the south over a mile of natural and restored dune
systems supports numerous rare species. This area
has also been colonized by the threatened western
snowy plover that nests in the dunes. If only the
California Department of Parks and Recreation, that
deserves great credit for their management of Silver
Strand, would apply their management skills to the
many miles of state beaches in Orange and Los
Angeles counties that are raked on a regular basis to
remove any shred of native flora and fauna.
Fig. 5. Sign at Redondo Beach bluff restoration area. This
is one of six signs educating the public about the value of
native plants and dunes. Photo by Kevin B. Clark
Clark: Remnant Coastal Dunes
Proceedings of the CNPS Conservation Conference, 17–19 Jan 2009
pp. 20–27
© 2011, California Native Plant Society
27
CONCLUSION
Coastal dunes in southern California represent a
paradox. They are one of the most heavily impacted
native communities and support some of the rarest
and most endangered plant and animal species, yet
much of their historic extent is publicly owned and
potentially restorable. While this means that buying
up large acreages for conservation is not necessary, it
also means that the solution lies in changing agency
management practices that are designed for the
recreational interests of millions of residents and
tourists. Beach raking represents the most pervasive
and continuing threat to these beaches, especially in
Los Angeles and Orange counties where dozens of
miles of beach are raked weekly.
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