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Loss of Coastal Strand Habitat in Southern California: The Role of Beach Grooming

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Abstract

We investigated the role of beach grooming in the loss of coastal strand ecosystems. On groomed beaches, unvegetated dry sand zones were four times wider, macrophyte wrack cover was >9 times lower, and native plant abundance and richness were 15 and >3 times lower, respectively, compared to ungroomed beaches. Experimental comparisons of native plant performance were consistent with our survey results: although initial germination was similar, seed bank, survival, and reproduction were significantly lower in groomed compared to ungroomed plots. Rates of aeolian sand transport were significantly higher in groomed plots, while native plants or wrack placed in that zone reduced sand transport. Our results suggest beach grooming has contributed to widespread conversion of coastal strand ecosystems to unvegetated sand. Increased conservation of these threatened coastal ecosystems could help retain sediment, promote the formation of dunes, and maintain biodiversity, wildlife, and human use in the face of rising sea levels.
Loss of Coastal Strand Habitat in Southern California:
The Role of Beach Grooming
Jenifer E. Dugan &David M. Hubbard
Received: 1 April 2009 / Revised: 29 September 2009 / Accepted: 6 November 2009 / Published online: 2 December 2009
#Coastal and Estuarine Research Federation 2009
Abstract We investigated the role of beach grooming in
the loss of coastal strand ecosystems. On groomed beaches,
unvegetated dry sand zones were four times wider,
macrophyte wrack cover was >9 times lower, and native
plant abundance and richness were 15 and >3 times lower,
respectively, compared to ungroomed beaches. Experimen-
tal comparisons of native plant performance were consistent
with our survey results: although initial germination was
similar, seed bank, survival, and reproduction were signif-
icantly lower in groomed compared to ungroomed plots.
Rates of aeolian sand transport were significantly higher in
groomed plots, while native plants or wrack placed in that
zone reduced sand transport. Our results suggest beach
grooming has contributed to widespread conversion of
coastal strand ecosystems to unvegetated sand. Increased
conservation of these threatened coastal ecosystems could
help retain sediment, promote the formation of dunes, and
maintain biodiversity, wildlife, and human use in the face of
rising sea levels.
Keywords Native plants .Aeolian sand transport .
Biodiversity .Beach .Beach zones .Ecotone .Coastal dune .
Hummock .Macrophyte wrack .Kelp
Introduction
Coastal strand and dune ecosystems exist at the narrow
dynamic boundary of land and sea (Fig. 1) that lies at the
forefront of sea level rise on open coasts. Composed of
unconsolidated sand from watersheds and coastal bluffs that
is constantly shaped by wind, waves, and tides, these
ecotonal habitats are strongly influenced by both marine
and terrestrial processes (Barbour 1992). These narrow,
extremely dynamic ecosystems support unique ecological
communities and functions (Barbour 1992; Brown and
McLachlan 2002; Schlacher et al. 2008). Like other
ecotones, coastal strand and dune ecosystems exhibit steep
gradients in biotic and environmental factors, are not static
in location and can be among the earliest to be influenced
by environmental stressors or drivers (Barbour 1992)
including precipitation (De Jong 1979), wave-driven sand
accretion and erosion, wind-driven sand transport, seawater
inundation and overwash events (Fink and Zedler 1990),
and salt spray (Barbour and De Jong 1977). Consequently,
coastal strand and foredune communities are subject to
dramatic cycles of erosion and accretion (Barbour and
Johnson 1988). Although many strand plant species are
perennial, they may be functional annuals in this dynamic
habitat.
Coastal strand and dunes are important features of the
worlds sandy coasts, the majority of which are already
classified as eroding (Bird 2000) often as a result of human-
induced changes in sediment supply and transport (Komar
1998). Rapid growth of human populations on the coast is
escalating pressure on coastal ecosystems at unprecedented
scales and amplitudes worldwide (e.g., Brown and
McLachlan 2002; Schlacher et al. 2007,2008). Coastal
evolution associated with climate change is expected to
further affect beach and coastal strand ecosystems (Defeo et
al. 2009; Feagin et al. 2005; Greaver and Sternberg 2007;
Harley et al. 2006; Schlacher et al. 2007,2008; Slott et al.
2006) with effects on biodiversity, community composition,
ecological function, and associated wildlife populations.
Coastal strand and dune ecosystems are thus increasingly
J. E. Dugan (*):D. M. Hubbard
Marine Science Institute, University of California,
Santa Barbara 93106-6150 CA, USA
e-mail: j_dugan@lifesci.ucsb.edu
Estuaries and Coasts (2010) 33:6777
DOI 10.1007/s12237-009-9239-8
squeezed between the impacts of intensifying seaside
development and the manifestations of climate change at
sea (Nordstrom 2000; Schlacher et al. 2007).
During the last century, large stretches of coastal strand
and foredune habitat have been lost in southern California
and elsewhere in the world through a combination of
coastal development and land use (Nordstrom 2000).
Fragmented by housing and resort development, road
construction, and coastal armoring, the remaining coastal
strand and dune habitats in the region experience heavy
human use and generally increased erosion, significant
reductions in sand supply, alteration of natural geomorphic
processes, and a variety of management activities including
grooming, berm building, and contouring. These human
alterations can severely limit the ability of coastal strand
ecosystems to adjust to changes in shoreline stability and
location (Clark 1996) and to sea level rise caused by
climate change (Schlacher et al. 2007).
Sandy beaches and associated coastal strand and dune
habitats support very high levels of recreation and tourism
in many parts of the world (Klein et al. 2004; Schlacher et
al. 2007; Whitmarsh et al. 1999). These areas are managed
with a wide variety of approaches ranging from hands-off
to intensive (Nordstrom 2000). Management for many
beaches includes the regular removal of marine wrack
(stranded macrophytes, e.g. kelps and seagrasses). In
southern California much of the sandy coast is mechani-
cally groomed or raked (>170 km) with heavy equipment
and specialized grooming machines to remove macrophyte
wrack (primarily kelps) and trash (Dugan et al. 2003).
A number of significant ecological impacts to the
intertidal biota of sandy beaches resulting from grooming
have been reported (Dugan et al. 2000,2003; Llewellyn
and Shackley 1996). These impacts propagate upward
affecting shorebirds and other higher trophic levels by
reducing invertebrate prey resources (Dugan et al. 2003).
Direct impacts of grooming or raking to nesting shorebirds,
such as snowy plovers (Page et al. 1995), and beach
spawning fish, such as the California grunion (Martin et al.
2006), have also been documented.
Routine grooming or raking of beaches can also alter the
distribution of native plants, local topography, and sediment
transport (Nordstrom 2000; Nordstrom et al. 2000,2006,
2007). To investigate ecological impacts of this widespread
management practice we quantified physical and biological
features of coastal strand habitats at groomed and ung-
roomed sandy beaches in southern California. We investi-
gated physical factors and the distribution of coastal strand
plants using comparisons of (1) beach zone widths, (2)
macrophyte wrack and plant cover, and (3) native plant
diversity and abundance on beaches with different groom-
ing regimes. We further evaluated the effects of grooming
on coastal strand vegetation by experimentally comparing
the population biology and performance of native coastal
strand plants, including seed bank, recruitment, growth,
reproduction, and survival on groomed and ungroomed
sections of a beach. We used three species thought to be
important in forming hummocks and initiating the
formation of foredunes on the California coast (beach
salt bush, Atriplex leucophylla; beachbur, Ambrosia
chamissonis; and sand verbena, Abronia spp. (De Jong
and Barbour 1979)), all classified as leading edge species
by Barbour (1992) in this experiment. We also examined
processes potentially affecting coastal strand vegetation by
comparing the relative short-term rates of aeolian sand
transport in (1) the above experimental treatments and (2)
the vicinity of fresh marine macroalgal wrack and a native
dune plant.
Methods
Surveys of Groomed and Ungroomed Beaches
We surveyed 24 different beaches (12 groomed and 17
ungroomed) on the southern California coast between Santa
Barbara and San Diego County, during the summer months
of 2001, 2002, and 2003 (Table 1). All beaches surveyed
are considered intermediate in morphodynamic state.
Surveys were restricted to summer when beaches are
expected to be widest and most stable in the region and
when strand vegetation is most likely to be present. We
selected wide beaches that were not constrained by
intertidal infrastructure (exposed seawalls, revetments, and
pavement) and avoided locations with river mouths or
extensive dune restoration.
To measure beach zone characteristics, we established
three shore-normal transects at each site. The upper end of
each transect was placed at the landward limit of the active
Drift line
Coastal strand
Foredune
Wrack
Swash zone
Extreme
high
water
Fig. 1 Generalized illustration of the locations of the zones used in
measurements in this study including the swash zone, the driftline,
wrack deposits, the coastal strand zone, extreme high water mark, and
the primary foredune on an ungroomed California beach. Groomed
beaches typically have very low amounts of wrack and no coastal
strand zone
68 Estuaries and Coasts (2010) 33:6777
beach (foredune toe, long-term vegetation line, or artificial
structure; Fig. 1). The transects were randomly spaced
along the shore (spacing between 5 and 50 m). To compare the
extent of unvegetated dry sand, we measured distance from
the landward limit of coastal strand vegetation, if present, to
the most recent high tide driftline on each transect (Fig. 1). If
no coastal strand vegetation was present, the distance from
the landward limit of the beach to the driftline was
considered the width of the unvegetated dry sand zone.
The cover and composition of dune vegetation and
wrack were measured with a line intercept method as used
in Dugan et al. (2003) along each of the three transects used
for zone width measurements as listed above. The extent of
all vegetation, wrack, debris, driftwood, or tar of 0.01 m or
more in width that intersected the transect line from the top
of the transect to the top of the active swash zone was
measured, categorized, and recorded. If no vegetation,
wrack or tar were present, no entry was made. The total
width of material encountered was then totaled for each
transect and the cover of vegetation and of wrack was
expressed in terms of total cover (meters).
For a subset of the mainland beaches listed in Table 1
with sufficient shoreline lengths, we established 1 km
length transects along each beach. We identified and
counted all plants seaward of the first dune ridge (or
artificial structure, bluff, or upland habitat edge where
dunes were absent) to estimate species richness and
abundance of native coastal strand and dune plants at each
beach. To evaluate differences among groomed and ung-
roomed beaches, we compared the abundance of native
dune plants on each 1 km transect including: red sand
verbena, Abronia maritima, pink sand verbena, Abronia
umbellata, beachbur, A. chamissonis, beach saltbush, A.
leucophylla, beach primrose, Camissonia cheiranthifolia,
and saltgrass, Distichlis spicata. Mean values of beach zone
widths, wrack cover, and plant cover, abundance and
species richness were compared for groomed and ung-
roomed beaches with a Studentsttest.
Field Experiment
The management regime (see below) used at San Buena-
ventura State Beach, Ventura County, California made it
possible to experimentally compare the performance of
native plants on groomed and ungroomed sections of the
same beach. Management of the beach park was zonal
with seasonal grooming (mechanical raking and sifting
between May and September each year) of the majority of
Table 1 Names and grooming status of beaches surveyed for use in comparisons of beach width, cover of wrack, and dune and coastal strand
plant cover, abundance and species richness
County Beach name
Ungroomed Groomed
Santa Barbara Haskells Beach Goleta Beach County Park
a
Sands Beach
a
Ledbetter Beach Park
a
East Depressions (UCSB) East Beach
Rincon County Park Carpinteria City Beach
Christi Beach, Santa Cruz Island
a
Sauces, Santa Cruz Island
a
Ventura San Buenaventura State Beach
a
San Buenaventura State Beach
McGrath State Beach Silverstrand Beach
Ormond Beach
unnamed, San Nicholas Island
a
Los Angeles Leo Carrillo State Beach Zuma Beach
Broad Beach Santa Monica State Beach
Dockweiler State Beach
Orange Huntington State Beach
a
Huntington State Beach
a
(Least Tern nesting exclosure)
San Diego Cocklebur, Camp Pendleton Del Mar, Camp Pendleton
a
Santa Margarita, Camp Pendleton Coronado City Beach
Silverstrand State Beach
Borderfields State Park
a
Denotes beaches where plants were not quantified on 1 km transects
Estuaries and Coasts (2010) 33:6777 69
the beach with the exception of the westernmost section,
which was ungroomed. When our experiment was initiated
in early 2002, that westernmost section had been left
ungroomed since 1999. We used the ungroomed section
and an adjacent groomed section of beach, located 400 m
apart, for our experiment. Established vegetated dunes and
dune vegetation inland of the extreme high water line were
present on both sections of the beach used in our
experiment.
We established experimental plots in the highest zone of
open sandy intertidal habitat (extreme high water, Fig. 1)in
both sections of San Buenaventura State Beach on 31
January 2002. This zone had been washed over by ocean
waves during storm events earlier in the month as indicated
by wrack deposits. The substrate was unvegetated well-
sorted beach sand in all plots. We set-up 24 plots of 5 m in
diameter (19.6 m
2
): 12 in the groomed section and 12 in the
ungroomed section. In each section, four plots were
randomly selected as replicates of each of three treatments:
(1) seeded and raked, (2) raked-only, and (3) unmanipulated
control. For each of the seeded plots, we raked the sand
surface, scattered fruits of three native dune plant species
(approximately 20,500 A. leucophylla, 8,100 A. chamisso-
nis, and 1,200 Abronia spp. fruits per plot), then raked sand
over them to retain the fruits. The sand surface was raked
twice in the raked-only treatment plots, and left undisturbed
in the control plots.
We counted the number of native plants visible at the
sand surface in the experimental plots at intervals from 23
Mar 2002 to June 2003, recording totals for each plot by
species and cohort. Some of the seedlings were covered
with sand during strong wind events and were not detected
on certain survey dates, but re-emerged and were counted
in later surveys. Recruitment (estimated by seedling
abundance) to the unseeded experimental plots during the
first winter (2002) was used as an estimate of the local
native seed bank present in groomed and ungroomed
sections of San Buenaventura State Beach. Differences in
recruitment observed between the beach sections were
expected to reflect differences in the densities of native
seeds in the local seed bank. We measured the length
(maximum horizontal extent in millimeters) of a sample of
first cohort seedlings in all of the seeded treatment plots on
30 March 2002 and recorded flowering and seed production.
The majority of the experimental results are reported as
means per plot. We used one-way nested analysis of
variance (ANOVA) to test for differences in recruitment
among treatments for each of two cohorts (Systat 5.2.1).
Differences in seedling size for each species were evaluated
with the Studentsttest. The survival of each cohort in the
seeded treatment plots was displayed as mean values (±1
standard deviation, n=4) of log (n+1)-transformed data for
each beach section.
Sand Transport Rates
To investigate an important physical process that can affect
dune plants and topography via sand deposition and loss on
groomed and ungroomed sandy beaches (Nordstrom et al.
2006,2007), we compared the relative rates of aeolian sand
transport under different experimental conditions. To
estimate aeolian sand transport rates, we used replicate
MWAC samplers (modified Wilson and Cooke samplers as
described and tested in Goossens et al. (2000)). This form
of portable and economical sampler was recommended
because of its high efficiency in aeolian sand trapping that
was found to be independent of wind speed in trials by
Goossens et al. (2000). In all trials, MWAC samplers were
deployed and maintained with the inlets located 1 cm above
the sand surface (to measure conditions experienced by
seedlings) and oriented to the prevailing wind during
measurements. Individual trials were conducted for 30 to
60 min. Sand accumulated in the samplers during each trial
was dried and weighed to the nearest milligram. Relative
rates of sand transport were calculated as kilograms per
hour per sampler due to the short-term nature and the intent
of the trials for use only in comparing conditions in our
experimental plots.
We estimated aeolian sand transport rates in the seeded
experimental plots in both sections of San Buenaventura
State Beach on three dates (22 April and 8 and 9 May
2003) with strong NW wind (averaging 5 to 8 m s
1
at 1 m
height above sand surface, 1 min means measured by a
hand-held Kestrel anemometer at the beginning and end of
each trial). We installed two MWAC samplers in each
seeded plot as described above and ran simultaneous paired
trials of 3060 min in the groomed and ungroomed sections
of the beach. Factors such as moisture characteristics and
the distance from swash uprush, vegetation lines, and dune
crests were controlled by the placement of sand traps in the
experimental plots, located at extreme high water line on
the open beach in front of established vegetated dunes. The
use of simultaneous trials in the groomed and ungroomed
sections of the study beach controlled for variation in wind
direction and velocity within each trial but not between
trials. The side onshore wind direction (NW) during the
trials minimized the potential influence of adjacent dune
topography on wind characteristics and sand trapping
(Nordstrom et al. 2006,2007).
We also experimentally compared the relative effects of
native dune plants and macrophyte wrack on aeolian sand
transport by measuring sand accumulation rates in MWAC
samplers deployed at different distances from a plant or
wrack pile during strong winds (averaging 7 to 9 m s
1
at
1 m height, measured as described above). Four replicate
arrays of five samplers each were deployed at 1 and 0.1 m
upwind, in the center, and 0.1 and 1 m downwind of an
70 Estuaries and Coasts (2010) 33:6777
individual plant (A. leucophylla) or a pile of fresh kelp pile
(Macrocystis pyrifera, 1 m diameter, 0.2 m height) located
or placed (kelp) near the extreme high tide line. In these
trials, sand traps were deployed in the same zone (extreme
high tide line) to control for variables such as sand
moisture, wind direction and velocity, distance from swash,
and other factors. Accretion was estimated by measuring
the depth of the sediment accumulated on the preexisting
beach surface at the end of the trial. These trials were
conducted on a south-facing beach on the University of
California at Santa Barbara campus with established dune
vegetation.
Results
Surveys of Groomed and Ungroomed Beaches
Grooming was associated with significant alterations in
beach zones, particularly in the widths of unvegetated
zones above the reach of typical tides and the presence of
zones with coastal strand vegetation. We found significant
differences in the widths of unvegetated zones landward of
the spring high tide levels between groomed and ungroomed
beaches in our comparative surveys. On average, these zones
were four times wider on groomed beaches (mean ± standard
deviation, 108±64 m) than ungroomed beaches (27 ± 9 m;
Fig. 2;ttest: t=5.618, df=32, p<0.0001).
The cover of macrophyte wrack, measured on the same
shore-normal transects as beach width, also varied signif-
icantly with grooming. Overall mean values for marine
wrack cover differed by >9-fold among groomed and
ungroomed beaches (0.24 m vs. 2.29 m, respectively, t
test: t=2.54, df=13, p=0.024; Fig. 3). Mean values of
cover of macrophyte wrack for individual beaches ranged
from 0.01 to 0.90 m for groomed beaches and from 0.07 to
5.44 m for ungroomed beaches.
In addition, we found a significant effect of grooming on
the cover, distribution, and abundance of coastal strand
vegetation. The overall average cover of coastal strand
plants on ungroomed beaches was 1.86 m (±2.45 m) with
mean values of plant cover ranging from 0.367.07 m for
individual beaches (Fig. 3). For groomed beaches no
measurable cover of coastal strand vegetation was detected
on the shore-normal transects used for beach width and
wrack measurements (Fig. 3). For the 1 km length shoreline
surveys, the abundance of native coastal strand plants was
16 times lower (9±20 individuals per kilometer) on
groomed beaches than on ungroomed beaches (149 ± 91
individuals per kilometer; ttest: t=4.986, df = 18, p<
0.0001; Fig. 4a). The species richness of native coastal
strand plants was also significantly lower (1.2±1.9 species
per kilometer) on groomed beaches than on ungroomed
beaches (4.3±1.7 species per kilometer; ttest: t= 3.803, df =
18, p<0.002; Fig. 4b). The abundance and species richness
of native coastal strand plants were not correlated with
beach width for groomed or ungroomed beaches.
Native Plant Performance
The local seed bank, as estimated by recruitment to the
unseeded experimental plots during the first winter (2002),
differed among the groomed and ungroomed sections of
San Buenaventura State Beach. Low numbers of seedlings
of two native species recruited in unseeded plots in the
ungroomed section (mean± 1 SD per 19.6 m
2
,n=8): A.
leucophylla (1.1±1.4) and A. chamissonis (0.8 ± 1.5) by 23
March 2002. In contrast, no native plants recruited in
unseeded plots in the groomed section in the first season.
During the second winter/rain season (2003) it was not
possible to distinguish recruits from the natural seed bank
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Un
g
roomed Groomed
Wrack
Vegetation
Cover (m)
Fig. 3 Mean values (±1 standard error) for wrack and coastal strand
vegetation cover on groomed and ungroomed beaches in southern
California
Latitude (de
g
rees N)
Width (m)
Ungroomed
Groomed
32 33 34 35
40
80
120
160
200
0
Fig. 2 Widths of the unvegetated zone above the driftline on groomed
and ungroomed beaches in southern California sampled in the summer
of 20012003
Estuaries and Coasts (2010) 33:6777 71
from those associated with the experimental manipulation.
However, more seedlings recruited into unseeded plots in
the second year than in the first. Seedlings of three species
had recruited into unseeded plots (mean ± 1 SD, n= 8): A.
leucophylla (ungroomed 123.8± 151.4, groomed 6.9 ± 12.7),
A. chamissonis (ungroomed 2.5± 2.5, groomed 2.6 ± 3.8),
and Abronia spp. (0.3± 0.5, groomed none) by 3 February
2003. No consistent pattern in Year 2 recruitment was
observed with respect to beach grooming. For A. leuco-
phylla, the mean number of recruits in Year 2 differed
significantly between groomed and ungroomed beach
sections (ttest: t=2.176, df=14, p< 0.05) but not for A.
chamissonis or the Abronia spp.
The recruitment of the three dune plants in the
experimental plots (estimated by seedling density) varied
among species, treatments, years, and beach sections
(Fig. 5). Overall, the recruitment of the three native species
introduced from seed to the experimental plots was quite
low for the 2 years: A. chamissonis = 3%, A. leucophylla=
5%, and Abronia spp.= 6% (total seedlings per added fruit).
In the first winter (2002), overall mean densities of
seedlings were similar (>10 m
2
) in the seeded treatment
plots in both the groomed and ungroomed beach sections
(Fig. 5). A single Abronia sp. recruited in a seeded plot in
the ungroomed section (Fig. 5). Transformed mean recruit
densities (log(x+1)) of two of the species (A. leucophylla
and A. chamissonis) varied significantly among treatments
but not consistently between groomed and ungroomed
sections (simple nested ANOVA, Atriplex, location: df= 1,
F=6.551, p=0.02; treatment (location): df = 4, F= 92.037,
p<0.0001; Ambrosia, location: df=1, F=0.456, p=0.51;
treatment (location): df= 4, F= 48.114, p<0.0001). Differ-
ences in densities of Abronia spp. were not tested because
of the low recruitment of this species in all treatments.
In the second rain season/winter (November 2002
March 2003), new recruitment of dune plants in seeded
plots was higher than observed in the first winter for all
three species in the ungroomed section, and lower for two
200100
50
2
4
6
8
150
0
Width (m)
b
200500
0
300 Ungroomed
Groomed
0
a
150
100
200
100
Number of species Number of individuals (#/km)
Fig. 4 a Abundance and bspecies richness of native coastal strand
and dune plants present seaward of the crest of the primary foredune
(or upland or artificial structure) as a function of width of the
unvegetated zone measured at groomed and ungroomed beaches
between Goleta and San Diego, California sampled in the summers of
20012003
1
10
100
1
10
100
1000
1
10
100
1000
1000
a Atriplex leucophylla
b Ambrosia chamissonis
c Abronia spp.
A
JJOJAJ
2002 2003
Date
Number (#/plot)
Number (#/plot) Number (#/plot)
Fig. 5 Mean numbers of native coastal strand plants: aA.
leucophylla,bA. chamissonis, and cAbronia spp., in 19.6 m
2
experimental plots seeded on 31 January 2002 (n= 4) in groomed
(solid circles and squares) and ungroomed (open circles and squares)
sections of San Buenaventura State Beach, California (circles cohort
one, squares cohort two)
72 Estuaries and Coasts (2010) 33:6777
of the species in the groomed section. However, seedlings
were not restricted to seeded plots in the groomed section,
suggesting seeds planted the previous year were dispersed
among the treatments by seasonal grooming activities
which occurred from late May through early September.
By 8 December 2002, seedling densities of all three species
in seeded plots were approximately an order of magnitude
higher in the ungroomed section than the groomed section
(Fig. 5). In the seeded plots, the maximum abundance of
seedlings of two of the species, Abronia spp. and A.
chamissonis, was recorded on 8 December 2002. Abun-
dance of seedlings of A. leucophylla increased through 20
March 2003, reaching a mean of 634.5± 402.4 individuals
per plot, while abundance of the other two species declined
during that period. There were significant location and
treatment effects for transformed mean recruit densities (log
(x+1)) of two species (A. chamissonis and Abronia spp.),
and a significant location effect for A. leucophylla (simple
nested ANOVA, Atriplex, location: df=1, F=13.023, p=
0.002; treatment (location): df=4, F=0.547, p=0.704;
Ambrosia, location: df= 1, F=6.053, p=0.02; treatment
(location): df =4, F=5.93, p=0.003; Abronia, location: df=
1, F=14.588, p=0.001; treatment (location): df= 4, F= 8.575,
p=0.0005).
Following recruitment, the survival of plants in experi-
mental plots varied significantly among groomed and
ungroomed sections of the beach in both years (Fig. 5). In
the plots in the groomed section, no plants survived through
spring in either year. In contrast, some plants survived
through the summer and fall months in plots in the
ungroomed section in both years. In the first year, although
seasonal mechanical grooming had not started, no plants
from the first cohort were visible in the experimental plots
in the ungroomed section by 1 May 2002. On that date, we
noted continuous wind-rippled texture on the sand surface
in the experimental plots of the groomed section and upon
excavation found some seedlings that had been buried by
wind-blown sand at approximately 5 cm depth. In the
ungroomed section, abundance had also declined by that
date but numerous plants from the first cohort were
observed in the experimental plots. By 8 December 2002,
early in the next rain season, the mean number of live A.
leucophylla plants from the first cohort had declined to 27 ±
26 per plot, and the two other species were represented by
single individuals in the experimental plots in the ung-
roomed section (Fig. 5).
In the second year of the study, the survival of the
second cohort of seedlings in experimental plots followed a
similar pattern to that observed in the first year for the plots
in the groomed and ungroomed sections of the beach.
Again, no plants from the second cohort remained in the
plots in the groomed section by the spring (11 April 2003)
prior to the onset of seasonal beach grooming (Fig. 5). On
that date, the surfaces of the plots in the groomed sections
were notably wind rippled. In the ungroomed section,
abundance had also declined by that date but numerous
plants from the second cohort were observed in the
experimental plots (Fig. 5).
Growth of two of the species, as estimated by mean sizes
in the early spring (measured as maximum horizontal
extent) during the first season, was significantly lower in
plots in the groomed section than the ungroomed section.
For A. leucophylla, mean sizes were 13.8 ± 3.3 mm (n= 61)
in the ungroomed and 10.8± 3.1 mm (n= 80) in the groomed
section (t=5.362, df=129, p< 0.001). For A. chamissonis,
mean sizes were: 14.8±2.9 mm (n= 70) in the ungroomed
and 12.6±3.3 mm (n=47) in the groomed section of the
beach (t=3.805, df=115, p<0.001).
Flowering and seed production of the three plants also
varied with species, treatment, and beach section. Two
species flowered and produced fruits in experimental plots
at the ungroomed site in both years: A. leucophylla and
Abronia spp. No flowering or seed production was
observed in plots in the groomed section of the beach.
Estimates of Aeolian Sand Transport Rates
The absolute rates of sand transport varied with wind speed in
all field trials and it is not valid to compare values across the
trials due to differences in the wind speeds during the trials
(Fig. 6). However, the relative rates of aeolian sand transport
measured in paired trials differed consistently between the
experimental plots in the groomed and ungroomed sections
of San Buenaventura State Beach in each trial. The relative
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
22 Apr
A
22 Apr
B
8 May
A
8 May
B
9 May
A
9 May
B
Groomed
Ungroomed
Mass (kg/hr)
Trial Date
Fig. 6 Relative mass of sand collected in aeolian sand transport
samplers (MWAC) during two sets of paired field trials on each of
three dates (22 April and 8 and 9 May 2003) in seeded experimental
plots in groomed and ungroomed sections of San Buenaventura State
Beach, California
Estuaries and Coasts (2010) 33:6777 73
rates of aeolian sand transport measured near the sand
surface were 10 to 1,000 times higher in seeded plots in the
groomed section than in the ungroomed section in simulta-
neous paired field comparisons in the six trials on three dates
(22 April and 8 and 9 May 2003; Fig. 6).
The presence of native plants and of macroalgal wrack
significantly affected relative rates of aeolian sand transport
in short-term field trials (0.51 h). The short-term effects of
established dune plants, A. leucophylla, and of newly
placed 1.0 m diameter by 0.2 m high deposits of fresh
giant kelp, M. pyrifera, wrack (fronds) on the relative rates
of wind transport of sand near the surface (1.0 cm height)
followed similar patterns (Fig. 7a, b). Sand trapping rates in
the center and immediately downwind of the plant or wrack
deposit were reduced by more than 90% of the rates
measured at 1.0 m upwind (Fig. 7a, b). For the dune plant,
the average rate of aeolian sand transport measured in the
center of the plants dropped to 4% of the rate measured
1.0 m upwind of the plants (Fig. 7a). Immediately (10 cm)
downwind of the plants, average sand transport rate was
less than 2% of the upwind rate. For experimental deposits
of the giant kelp, M. pyrifera, the average rate of sand
transport in the center of the piles of kelp was <1% of the
rate measured 1 m upwind. Immediately downwind of the
kelp deposits, the average rate of sand transport was 6% of
the upwind rate (Fig. 7b). Sand accretion of up to 5 cm h
1
was noticeable on the upwind side of the plants and on the
freshly placed wrack piles, particularly at the 0.1 m
position, during the field trials.
Discussion
Results from our study indicate that beach grooming or
raking can have negative impacts on coastal dune and
strand habitats and vegetation through direct and indirect
effects. Our field survey results suggest that a large scale
conversion of coastal strand ecosystems to unvegetated
barren habitats has occurred on groomed beaches through-
out southern California, a trend noted for developed coasts
by Nordstrom (2000). Many of the open coast beaches that
appeared to be very wide are more likely composed of a
narrow zone of actual intertidal beach below the extreme
high water line and above that a much wider zone of
degraded coastal strand and dune habitat that is not often
washed by tides. Our observations in California and those
of others (Nordstrom 2000; Nordstrom et al. 2000) strongly
suggest that these unnaturally wide beaches, if left ung-
roomed, can gradually recover coastal strand and dune
vegetation over much of the unvegetated dry sand zone. For
example, the ungroomed section at San Buenaventura State
Beach developed coastal strand vegetation and hummocks
that extended 2040 m seaward of the vegetated foredune
<4 years after all grooming was suspended. This recovery
did not occur in the adjacent seasonally groomed section of
the beach during the same period.
The results from our field experiment on native coastal
strand plant performance were consistent with the patterns
observed in our field surveys of groomed and ungroomed
beaches. Performance of native coastal strand and dune
plants was generally higher in plots in the ungroomed
section of the beach. Although initial germination rates
from added seed were quite similar in the groomed and
ungroomed sections, seed bank, survival, and reproduction
were significantly lower in the groomed section. Native
coastal strand plants in plots located in the seasonally
groomed section of San Buenaventura State Beach
exhibited almost no recruitment from local seed bank, grew
more slowly, did not survive into summer, and failed to
flower or reproduce during the course of the experiment.
According to Barbour (1992) plant species, such as A.
leucophylla and A. chamissonis used in our experiment,
that are typical of the leading edge are expected to be more
tolerant of salt spray, soil salinity, and drying winds.
However, newly recruited plants in the groomed section
appeared to be overwhelmed by the unstable sand sheet and
sand movement produced by the seasonal beach grooming
regime and died before the annual onset of grooming.
Analyses of coastal dunes on a barrier island by Looney
and Gibson (1995) indicated that seed bank development
0.00
0.02
0.04
0.06
0.08
0.10
1.0 0.1 0.0 -0.1 -1.0
a
0.00
0.02
0.04
0.06
0.08
0.10
1.0 0.1 0.0 -0.1 -1.0
b
Mass (kg/hr)
Mass (kg/hr)
Distance (m)
Fig. 7 Relative mass (mean ± one standard deviation, n= 4) of sand
collected in aeolian sand transport samplers (MWAC) arrayed at
distances up and downwind of aindividual native dune plants, A.
leucophylla, and bindividual 1-m diameter piles of kelp wrack, M.
pyrifera, in two short-term field trials in late April 2003
74 Estuaries and Coasts (2010) 33:6777
scaled with disturbance frequency and time since distur-
bance, as well as successional state. Their study found that
seed banks were poorly developed and more transient in
frequently disturbed coastal strand habitat and dredge spoils
than in wooded dunes. Our findings suggest that disturbance
associated with beach grooming results in an extremely
reduced seed bank for coastal strand vegetation relative to
ungroomed beaches on the California coast. Along urban-
ized and groomed shorelines the resulting paucity of seed
sources from littoral transport may further intensify the
effects of this loss of local seed bank and active restoration of
strand vegetation may be required in such areas.
Although initial recruitment from added seed was similar
in experimental plots in the groomed and ungroomed
sections in the first season, it differed substantially by the
second season of observation, suggesting that additional
factors may have influenced recruitment from the originally
added seed in the second season. The recruitment of native
plant seedlings was lower and not restricted to seeded plots
in the groomed section, while overall recruitment was
higher in seeded plots in the ungroomed section. Natural
processes and human activities that differed between the
groomed and ungroomed beach sections may have contrib-
uted to this variation including the redistribution of seeds or
fruits by pocket gophers, Thomomys bottae (ungroomed
section only), wind and park users (both sections), or
grooming (groomed section only), the reproduction and
short distance dispersal of A. leucophylla and Abronia spp.
fruits (in the ungroomed section only), and the deposition
of fruits produced elsewhere by storm tides (ungroomed
section) or wind (both sections).
Grooming or raking to remove macrophyte wrack and trash
also alters the physical characteristics of intertidal beach,
coastal strand, and dune habitats including micro-topography
and zonal distinctions. Mechanical alteration of the sand
surface by heavy equipment during grooming results in the
direct destruction of existing vegetation, hummocks, and
embryo dunes, and the alteration of other features, including
beach profile and topography (Nordstrom 2000;Nordstromet
al. 2000; Roig i Munar 2004). Although storm and overwash
events create flat surfaces on beaches, with sufficient
intervals between disturbance events, these are transformed
by natural processes that lead to vegetated hummocks and
eventually dunes (Bauer and Sherman 1999). Our results, in
agreement with Nordstrom (2000), suggest that the regular
disturbance of grooming, as practiced on many beaches,
encourages the persistence of wide dry sand zones with very
low vegetation cover and diversity.
Hummocks and small dunes form where sand movement
is slowed by vegetation or other debris, including macro-
phyte wrack and driftwood (Barbour and Johnson 1988;
Bauer and Sherman 1999; Hesp 2002; Nordstrom et al.
2000,2006,2007). These features further influence
landward wind and sand transport patterns, which then
allows for colonization by plant species associated with
more stable dunes (Barbour and Johnson 1988; Hesp 2002;
Nordstrom 2000; Nordstrom et al. 2000). Although we
found similar short-term effects of wrack and a native plant
on sand transport, as native plants grow in size, they are
able to trap more sand, resulting in further development of
hummock and dune forms, while wrack provides only a
temporary effect on sediment trapping (Nordstrom et al.
2006,2007). A key indirect effect of grooming thus appears
to be the removal of both macrophyte wrack and native
plants (including propagules and seeds), as well as
driftwood and cobbles, all of which can potentially act as
ecosystem engineers that reduce saltation of wind-blown
sand particles and initiate the processes of hummock and
embryo dune formation (Hesp 2002). Continued develop-
ment of hummocks and foredunes in this ecotone is greatly
enhanced by the presence and growth of colonizing coastal
strand vegetation, the propagules of which may be
delivered with wrack and other drift deposits (e.g. Hesp
2002; Nordstrom et al. 2000). We observed relatively
greater (orders of magnitude) wind-driven sand transport
in our experimental plots on a groomed section compared
to an ungroomed section of a beach in every pair of short-
term comparisons. Although not indicative of absolute sand
transport rates, these results suggest that on beaches with
reduced vegetation cover and wrack accumulation associ-
ated with grooming, wind-driven sand transport can be
relatively greater than on ungroomed beaches contributing
to reduced seedling survival as seen in our study. In
agreement with Nordstrom et al. (2006,2007), our results
imply that by removing macrophyte wrack and reducing the
performance and cover of native strand plants, beach
grooming or raking could affect the dynamics of sediment
accumulation, retention, and loss on sandy beaches. By
extension, environmental drivers that affect the supply and
delivery of drift macrophytes from reefs and seagrass beds
to beaches (Reed et al. 2008) could also be expected to
indirectly influence sediment dynamics and topographic
evolution of beach and coastal strand ecosystems.
The removal of wrack by grooming may also indirectly
modify the distribution of soil moisture and nutrients
needed for plant growth with important implications for
plant performance and resulting coastal strand and dune
evolution. The productive nearshore kelp forests and reefs
of the region (Reed et al. 2008) export large quantities of
drift material, much of which is deposited on beaches
(Hobday 2000; Lastra et al. 2008). In addition to initiating
the formation of hummocks and embryo dunes by wind-
driven sand, macrophyte wrack, particularly kelps, can be
rapidly consumed and processed by intertidal detritivores
(Lastra et al. 2008) creating particulates that are washed
into the sand by waves and tides, subjected to microbial
Estuaries and Coasts (2010) 33:6777 75
activity and remineralized. High levels of nutrients in the
beach aquifer have been associated with a high standing
stock of wrack on California beaches (Dugan et al.
unpublished), suggesting wrack may be a source of
nutrients in this coastal ecosystem. This, in turn, may have
implications for the success and nutrient status of coastal
strand and dune vegetation on groomed beaches via bottom
up effects, as reported for plants and seabird roosts on
desert islands by Anderson and Polis (1999).
Our observations suggest that the section of San
Buenaventura State Beach where grooming had ceased for
4 years was gradually recovering ecological value as
indicated by the development of embryo dunes and
hummocks between the extreme high water mark and the
driftline, increased sand stability, the seaward expansion of
vegetation (2040 m), and the significantly higher perfor-
mance of plants observed in our experiment. A similar
response to the cessation of grooming was illustrated by
Nordstrom et al. (2000) and Nordstrom (2000) for a beach
in New Jersey and could be expected for other beaches
where grooming was suspended for sufficient periods of
time. For coastal managers and others concerned with
restoring intertidal and coastal dune and strand ecosystems
while maintaining high recreational use beach areas, a
scheme of grooming in which designated longshore
stretches or islandsof beach are left ungroomed year-
round, could represent a far more ecologically effective
approach than seasonal grooming of the entire stretch of
beach. Determining the length and spacing of ungroomed
islandsof beach shoreline needed to effectively conserve
coastal strand ecosystems for coasts with high human use
may require additional study.
Located on the boundary of a rising and warming ocean
and a growing populace, coastal strand ecosystems are
losing ground on the southern California coast and
elsewhere. The ecosystem services and functions provided
by these dynamic coastal ecotones have no analogs, yet are
profoundly threatened by the combination of sea level rise
and ongoing losses to widespread human activities (e.g.
Feagin et al. 2005; Greaver and Sternberg 2007), including
the impacts of beach grooming as demonstrated here.
Dynamic processes that link functional coastal strand ecosys-
tems with the development of dune forms (Hesp 2002;
Nordstrom et al. 2000) are worthy of consideration as well.
In the face of rising sea level, new management approaches
and timely conservation and restoration of these ecosystems
may assist in retaining sediments and providing buffers to
maintain biodiversity, wildlife, and human use on the coasts.
Acknowledgements We thank D. Chakos, M. Lastra, M. Lippincott,
J. Tarmann, and A. Webster for their dedication and enthusiastic
assistance with all aspects of field and laboratory work. We gratefully
acknowledge K. Samis for her measurements of beaches on the
northern Channel Islands in 2003. We extend special thanks to V.
Gardner, Resource Ecologist for California State Parks, Channel Coast
District, for making this research possible at San Buenaventura State
Beach. We thank V. Gardner, C. Roye, and two anonymous reviewers
for constructive comments on earlier versions of this manuscript. This
research was supported by funding to J. Dugan from (1) the California
Sea Grant Program Project # R/CZ-174 under NOAA Grant
#NA06RG0142 through NOAAs National Sea Grant College Pro-
gram, U. S. Department of Commerce; (2) California Department of
Parks and Recreation, Channel Coast District; and (3) the Santa
Barbara Coastal LTER funded by the National Science Foundation
(Award # OCE-9982105 and OCE-0620276). The statements, find-
ings, conclusions, and recommendations are those of the authors and
do not necessarily reflect the views of California Sea Grant, California
State Parks, the National Science Foundation or the U.S. Dept. of
Commerce.
Conflicts of Interest Notification The authors hereby state that they
do not have a financial relationship with the organization that
sponsored the research and that no potential conflicts of interest exist
to our knowledge and understanding. We maintain full control of all
primary data and we agree to allow the journal to review our data if
requested.
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Estuaries and Coasts (2010) 33:6777 77
... Wood deposited on coastlines can help to trap and retain mobile sediment, reducing coastal erosion rates (Eamer & Walker, 2010) and facilitating the formation of sand dunes (Heathfield & Walker, 2011) and taller berm crests on gravel beaches (Kennedy & Woods, 2012). Driftwood on sandy coastlines can enhance native plant abundance and richness (Dugan & Hubbard, 2010), help to retain organic matter, and provide nutrients and habitat for multiple species of invertebrates (Gheskiere et al., 2005). Wood in rocky intertidal zones provides nutrients, habitat, and refuge from predation for invertebrates (Kano et al., 2013;Storry et al., 2006). ...
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Coasts form the universal stage on which people interact with the global ocean. Our history is inextricably intertwined with the seashore, being a rich tapestry of archaeological sites that paint a vivid picture of people hunting, foraging, fishing and scavenging at the edge of the sea. Seascapes inspire diverse art forms celebrated through the ages. The world's sandy beaches have a flummoxing duality of anthropocentric purpose-ranging from the horrors when being theatres of war to first love under a rising moon. 'Man's Love of the Sea' continues to draw people towards the shore: the narrow coastal strip contains everything from holiday cottages to mega-cities. This coastal concentration of the human population is problematic when shorelines erode and move inland, a geological process fastened by climate change. Society's response is often a heavy investment in coastal engineering to complement and enhance the natural storm protection capacity of beaches and dunes. The coast's immense cultural, social, and economic significance are complemented by a wealth of natural riches. In the public's eye, these ecological values can pale somewhat compared with more imminent ecosystem services, particularly protecting human properties from storm impacts. To re-balance the picture, here we illustrate how peer-reviewed science can be translated into 'cool beach facts', aimed at creating a broader environmental appreciation of ocean shores. The colourful kaleidoscope of coastal values faces a veritable array of anthropogenic stressors, from coastal armouring to environmental harm caused by off-road vehicles. Whilst these threats are not necessarily unique to coastal ecosystems, rarely do the winds of global change blow stiffer than at the edge of the sea, where millions of people have created their fragile homes on shifting sands now being increasingly eroded by rising seas. Natural shorelines accommodate such changing sea levels by moving landwards, a poignant and powerful reminder that protecting the remaining natural land is primus inter pares in coastal management. There is no doubt that coastal ecosystems and coastal communities face august trials to maintain essential ecosystem services in the face of global change. Whilst bureaucracies are not always well equipped to counteract environmental harm effectively, using measures carrying a social license, many communities and individuals have encouragingly deep values connected to living coastlines. Building on these values, and harnessing the fierce protective spirits of people, are pivotal to shaping fresh models that can enhance and rebuild resilience for shores that will continue to be a 'baroque embarrassment of coastal riches'.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Chapter
Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward.
Book
The text begins with an introduction to concepts and terminology, and the factors that have affected coastal evolution and coastline changes (Chapter 1). This is followed by a discussion of waves, tides, currents and other nearshore processes (Chapter 2), and a study of the effects of land and sea level changes, notably the Holocene marine transgression, which has played a major part in shaping modern coastlines and can be regarded as a unifying theme in coastal geomorphology (Chapter 3). Cliffs are discussed in Chapter 4 and the shore platforms that border them in Chapter 5. Chapter 6 deals with the origin of beaches and the changes taking place on them, and Chapter 7 with the beach erosion problem. Spits, barriers and bars are discussed in Chapter 8 and the formation of coastal dunes in Chapter 9. Intertidal wetlands, including mudflats, salt marshes and mangroves are dealt with in Chapter 10, followed by estuaries and lagoons, including other inlets (rias, fiords, fiards, calanques, sharms and sebkhas) in Chapter 11. Chapter 12 considers deltas produced by deposition at river mouths, and Chapter 13 reviews coral and algal reefs. Chapter 14 deals with future coasts. There are 187 illustrations and 15 tables. Details of articles cited are given in the References section, which includes many pre-2000 publications that remain relevant.
Book
This book is divided into four major categories: management strategies (goals, development impacts, management solutions, strategy planning and program development); management methods (for aquaculture, coral reefs, environmental impact assessment, mangroves, and water quality management, for example); a management information base (for 110 different subjects eg agriculture, beach erosion, economic valuation, ecotourism, global warming, natural hazards, pollution and socio-economic factors); and 47 case histories from Australia, the Caribbean, the Indian Ocean, South-East Asia, and North America.
Chapter
This chapter discusses the morphological traits of beach plants, especially those at the leading edge of vegetation. It focuses on three of the four North American coastlines: (1) Atlantic, (2) Gulf of Mexico, and (3) Pacific Coasts. The studies described in the chapter include zonation data to distinguish the species at the leading edge of vegetation from those characteristic of the rest of the beach and from those that typify more stabilized dunes behind the foredune. Taxonomic diversity from coast to coast is resolved into a small pool of growth-form syndromes. Each syndrome is selected through evolutionary time as being adaptative to the beach habitat, and the value of a given trait can be estimated by computing the percentage of the flora that share it. The basic cause-and-effect nature of those adaptations is revealed only by laboratory experimentation and field manipulation.
Article
(1) Plant and soil-water variables were monitored at monthly intervals for a year on two Californian beaches. (2) Plant xylem-sap tensions were greater in plants at the warmer, drier, southern California site than in plants at the cooler, wetter, northern California site, but did not approach levels typical of extreme xerophytes. The species Atriplex leucophylla (Moq.) D. Dietr. and Cakile maritima Scop. had the greatest seasonal changes in dawn xylem-sap tension, whilst Abronia maritima Nutt. ex Wats. and Ambrosia chamissonis Less. had low dawn xylem-sap tensions throughout the year. (3) Measurements of soil-water concentration and soil-water potential showed that the sand at 100 cm depth remained relatively moist throughout the year, but during rainless periods it dried out at shallower depths. The soil water-table depth varied little throughout the year and the salinity of water below it was always less than 3% that of seawater. The concentration of salt in sand generally decreased inland from the ocean. Calculated soil osmotic potential was between 0 and - 10 bar at 100 cm depth, but substantially less at shallower depths. (4) Evidence is presented to explain the source of water available to beach plants during extended rainless periods. Field phenology and growth patterns are discussed in relation to the seasonal course of water relations and temperature.
Article
Atriplex leucophylla is an evergreen perennial which grows between 39⚬30'N and 28⚬N at the seaward edge of Californian beach vegetation. It has a northern form (NF, exemplified by material from Bodega Bay) and a central-southern form (SF, exemplified by material from Trancas). NF has genotypically smaller leaves, thinner stems, a larger leaf:stem weight ratio, smaller specific stem and leaf weights, and a more prostrate habit, as revealed by field and growth chamber studies. NF germinates later, devotes less time to sexual reproduction, and grows vegetatively later into the fall. Xylem sap tensions in nature were more negative for SF. Optimum germination temperature for both was 25⚬ C, but NF had a narrower range of temperature for significant germination. The photosynthetic response to light was the same for both (3 nmole CO2 cm-2 sec-1 at 200 nEinstein cm-2 sec-1). The photosynthetic temperature optimum for NF was 2⚬ C above that for SF and the optimum was considerably above natural leaf temperatures. Field measurements of environmental factors led us to conclude that some ecotypic differentiation was related to gradients in physical stress, particularly sand movement or salt spray.
Article
Twelve taxa, characteristic of beach vegetation along the Pacific Coast of the United States, were grown from seed and subjected to realistic levels of salt spray (50 mg dm-2 day-1) and seawater inundation (residual soil salinity of 3,328 ppm). Mortality, morphology, and biomass were measured and combined in a tolerance index. For most taxa, this tolerance index correlated well with zonation position in the field (average plant position from tide line inland to foredune; r > 0.85). Three or four taxa behaved anomalously, exhibiting either much more or much less tolerance than expected from their zonation position, and we conclude that a single-factor approach is too naive to account for the distribution of all beach taxa.
Book
This volume discusses the role of humans in transforming the coastal landscape. The book details the many ways beaches and dunes are eliminated, altered and replaced and the differences between natural landforms and the human artefacts that replace them. Emphasis is placed on the importance of retaining naturally functioning beaches and dunes in ways that achieve natural values while accommodating development and use. The issues dealt with in this book will be of interest to practising coastal engineers and research scientists, as well as to planners and managers of coastal resources at all levels of government. It will be of particular value to investigators planning for the future of coastal development under accelerated sea level rise. The book will also be useful as a reference text for graduate and advanced undergraduate courses in geography, geology, ecology and other disciplines dealing with the interaction between science, technology and society.