Dune Vulnerability in Relation to Tourism Pressure in Central Gulf of Cádiz (SW Spain), a Case study

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Dune Vulnerability in Relation to Tourism Pressure in Central Gulf of Cádiz (SWSpain), a Case studyAuthor(s): Sara Muñoz Vallés, Juan B. Gallego Fernández, and Claudia M. DellafioreSource: Journal of Coastal Research, 27(2):243-251. 2011.Published By: Coastal Education and Research FoundationDOI: http://dx.doi.org/10.2112/JCOASTRES-D-09-00125.1URL: http://www.bioone.org/doi/full/10.2112/JCOASTRES-D-09-00125.1

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Dune Vulnerability in Relation to Tourism Pressure inCentral Gulf of Cadiz (SW Spain), a Case study

Sara Munoz Valles, Juan B. Gallego Fernandez, and Claudia M. Dellafiore

Universidad de SevillaDepartamento de Biologia, Vegetal y EcologiaAvda. Reina Mercedes, S/NSeville 41012, [email protected]

ABSTRACT

MUNOZ VALLES, S.; GALLEGO FERNANDEZ, J.B., and DELLAFIORE, C.M., 2011. Dune vulnerability in relation totourism pressure in central Gulf of Cadiz (SW Spain), a case study. Journal of Coastal Research, 27(2), 243–251. WestPalm Beach (Florida), ISSN 0749-0208.

The severe modification and progressive loss of coastal dunes in the last decades has resulted in calls fromconservationists to assess the conservation status and condition of these systems, and thus several vunerability indiceshave been developed. The vulnerability status of two protected coastal dune systems in the central Gulf of Cadiz (SWIberian Peninsula) was assessed at local scale and results compared with a previous assessment to regional scale. Avulnerability index (VI) based on variables that desribed geomorphological condition, marine influence, aeolianinfluence, vegetation condition, and human effects was calculated to previously defined 17 homogeneous coastalsegments, and the main factors affecting them were identified. Higher vulnerability was related to two differentiatedsituations: segments with low or negative sedimentary budget and segments subjected to considerable human pressure.Vulnerability status of the studied stretches was also analyzed in relation to tourism pressure and level of accessibility.Vulnerability was directly related to some characteristics of the accesses as well as to visitor pressure, showing highervulnerability those segments with increased accessibility and influx of visitors. Obtained results were more detailed incomparison with previous assessment to regional scale, and were easily translated to specific management actions. Theseactions should be mainly focused on controlling and limiting human (tourism) influence, particularly in those segmentsaffected by these factors.

ADDITIONAL INDEX WORDS: Coastal dune management, dune vulnerability index, local-scale assessment.

INTRODUCTION

As the result of an excessive exploitation of natural resources

and services that they offer, an excessive population growth,

and urban and industrial development, many coastal dune

ecosystems are nowadays being seriously altered worldwide,

some of them irreversibly affected (Carter, 1988; Heslenfeld,

Jungerius, and Klijn, 2004; Martınez, Psuty, and Lubke, 2004;

Williams et al., 2001; Williams, Randerson, and Sothern, 1997).

Since 1900, it has been estimated that approximately 25% of

coastal dune areas has been lost in Europe and 55% of the

remaining areas has lost its natural quality, with 85% of these

existing coastal dunes currently endangered (Heslenfeld,

Jungerius, and Klijn, 2004). This severe modification has

resulted in the last decades in calls from conservationists to

assess the condition of these systems. Over the last years,

various indices have been proposed to assess dune vulnerabil-

ity to natural and human-induced disturbances, considering

hydrodynamic, climatic, or human impacts (Cooper and

McLaughlin, 1998; Garcıa Mora et al., 2001; Williams et al.,

2001). In this framework, vulnerability refers to the capacity

that a particular ecosystem has to absorb disturbance without

undergoing permanent alterations, being an antonym of the

concept of ‘‘elasticity’’ (Orians, 1975) or ‘‘resilience’’ (Pimm,

1991) . The main objective to the use of these indices is to

identify homogeneous units in the coastal zone and to classify

them to predict the system response to environmental

variations, as well as to develop appropriate management

strategies (Garcıa Mora et al., 2001; Williams et al., 2001). This

approximation can also be used repeatedly to evaluate a

particular system through time to assess the effectiveness of

adopted management measures, as well as to compare

vulnerability of systems to different scales (Williams et al.,

1993). The application of these indices has been useful in dune

vulnerability assessment at a regional scale in different

countries around the world, such as France (Bodere et al.,

1991), United Kingdom (Williams et al., 1993), Portugal

(Alveirinho Dias et al., 1994; Matias et al., 1998), Spain (Garcıa

Mora et al., 2001), Turkey (Marlow and Morris, 2003), or

Mexico (Martınez et al., 2006).

On the other hand, coastal dunes are considered at present

among the most demanded habitats for recreational use

(Kutiel, Zhevelev, and Harrison, 1999; Williams, Randerson,

and Sothern, 1997), with the resulting tourism and its

associated impacts one of the main threats to these ecosystems

(Heslenfeld, Jungerius, and Klijn, 2004; Kutiel et al., 2004;

Kutiel, Zhevelev, and Harrison, 1999; Martınez, Psuty, and

DOI: 10.2112/JCOASTRES-D-09-00125.1 received 31 August 2009;accepted in revision 7 February 2010.’ Coastal Education & Research Foundation 2011

Journal of Coastal Research 27 2 243–251 West Palm Beach, Florida March 2011

Lubke, 2004; Nordstrom, 2008; Nordstrom, Lampe, and

Vandemark, 2000). Derived impacts from tourism range from

direct loss of dune habitat by urban and facilities building to

the environmental degradation by pressure of use on the

surrounding natural areas (Gallego Fernandez, Garcıa Mora,

and Ley Vega de Seoane, 2003; Garcıa Mora, Gallego

Fernandez, and Williams, 1998; Martınez, Psuty, and Lubke,

2004; Nordstrom, Lampe, and Vandemark, 2000). In addition,

intensive and uncontrolled visitor traffic in the coastal dunes,

as well as other entertainment activities, can cause serious

alterations in the environment (soil compression, overland

seawater flow, loss of vegetation cover and erosion; Andersen,

1995a; Heslenfeld, Jungerius, and Klijn, 2004; Kutiel, Zheve-

lev, and Harrison, 1999), where trampling is one of the most

damaging derived impacts (Andersen, 1995b; Baeyens and

Martınez, 2004; Brown and McLachlan, 1990; Nordstrom,

Lampe, and Vandemark, 2000; Williams, Randerson, and

Sothern, 1997).

Since the beginning of the 1960s, the Gulf of Cadiz coast has

been transformed by a largely uncontrolled urban develop-

ment, resulting in highly developed coastal stretches inter-

spersed with some protected coastal areas, such as Donana, the

Rompido spit, or Enebrales de Punta Umbrıa. Road construc-

tion and marine engineering activities have interfered in

addition with natural sedimentary processes (Garcıa Mora,

Gallego Fernandez, and Williams, 1998; Ojeda Rivera et al.,

1993). Specifically, the coast of Huelva is an important tourist

destination, with more than 1 million people visiting it between

May and September (Rodrıguez Ramırez et al., 2003). The

management of this coast has been mainly focused on beach

nourishment, coastal erosion protection (construction of

groins), and the building of marine walks (Garcıa Mora,

Gallego Fernandez, and Williams, 1998; Munoz Perez et al.,

2001), such activities interfering with the natural sedimentary

processes (Borrego, Morales, and Pendon, 1992). At a local

level, administrations have focused their efforts on the creation

of infrastructures and beach facilities, residuals collection,

container establishment, and environmental education pro-

grams. Nevertheless, most of these measures can destroy the

beach and dune vegetation and damage the geomorphology of

the dune system (Garcıa Mora, Gallego Fernandez, and

Williams, 1998).

The aim of this study was to assess coastal dune vulnerability

along a segment of the Gulf of Cadiz coastline at a local scale to

identify the main factors affecting dunes and to relate

vulnerability condition to differential visitor pressure and

accessibility degree. Results were expected to provide a basis

for designing specific management approaches.

STUDY AREA

A discontinuous coastal strecth of 15 km in the Gulf of Cadiz

central section was studied, corresponding to the sand spit of El

Rompido at the west, and to Enebrales de Punta Umbrıa dunes

at the east (Figure 1). Both are protected areas, mainly

consisting of incipient transverse dunes and foredunes largely

continuous along the shore length and showing some parabolic

and barchanoid dunes inland. Foredunes are relatively narrow

in both cases, ranging from 2 to 4 m high. Tidal regime is

mesotidal and semidiurnal and climate is warm-temperate

(Borrego, Morales, and Pendon, 1993), framed into a Mediter-

ranean climate with oceanic influence. Mean annual temper-

ature is 18.2uC and mean annual rainfall is 620 mm. Prevailing

SW winds in the coastal frame (Dabrio, Boersma, and

Fernandez, 1982) bring 74% of swell from SW, with a

medium-low energy regime (Dabrio and Polo, 1987).

The spit of El Rompido is located at the Piedras River estuary

(Figure 1), deriving from an older barrier island that joined to

the mainland. It stretches for about 12 km along the coast, its

width varying from 300 to 700 m, steadily growing to the East

at mean annual rate of 39.5 m in the last 130 years (Munoz

Valles, unpublished data). The tourist settlement of La Antilla

Figure 1. Location of the study area (spit of El Rompido and Enebrales de Punta Umbrıa) in the coast of Huelva province (central Cadiz Gulf, SW Spain).

244 Munoz Valles, Gallego Fernandez, and Dellafiore

Journal of Coastal Research, Vol. 27, No. 2, 2011

is located at its western end. Access to the beach is facilitated by

an asphalted road crossing salt marshes and dunes. At the

study date and at the end of this road, connecting it with the

settlement, a pathway running parallel to and backward from

the foredune provided access to the beach by several non-

prepared pathways, mainly used by pedestrians. In addition,

two wooden walkways ran across the width of the spit, being

respectively located at about 4.5 km and 9 km east from the

settlement (Figure 2a). Boat services provided visitors with

access to the walkways and to the area at the eastern end of the

spit by crossing the river.

Enebrales de Punta Umbrıa is located near the eastern

end of the spit, in the continental side (Figure 1). This

dune system extends along 2.8 km of shore and between

350 and 1400 m inland. The town of Punta Umbrıa is located

at the eastern end of this area. The dune system is truncated

at about 500 m landward by an asphalted road running

parallel to the coastline, providing access to six wooden

walkways that cross the dune system and connect the road

with the beach (Figure 2b). All of these walkways finished

behind the foredune and not in the open beach at the

vulnerability study date; pathways cutting across the foredune

extended to the beach.

METHODS

Coastal dune vulnerability was assessed following a check-

list that was previously applied along SW Spain and Portugal

at a regional scale (Garcıa Mora et al., 2001). This checklist

comprises 54 variables grouped into 5 partial vulnerability

indices as follows: geomorphological condition of the dune

(GCD) (8 variables), marine influence (MI) (8 variables),

aeolian influence (AI) (9 variables), vegetation condition (VC)

(10 variables), and human effect (HE) (17 variables) (see Garcıa

Mora et al., 2001). GCD partial index is related to the

geomorphological and sedimentary factors affecting the effi-

ciency of the system to buffer extreme waves and wind:

typology and extent of the coastal dunes (sand supply),

existence and extent of wet slacks in the inner dunes, and

sand particle size, mainly. MI considers factors related to

marine erosion procesess: wave action variables (i.e., height,

length, energy), tidal range, coastal exposure, beach slope,

dune system seaward development, and particle size. Aeolian

influence is related tothe role of aeolian processes, largely

depending on the ratio between sand supply and deflation. It

takes into account sand supply input, cover of embryo dunes,

percentage of blowouts and deflation breaches not induced by

trampling in the foredune, sea litter, shells and pebbles

covering on the beach, and vegetation covering aspects.

Vegetation condition is related to the key role that vegetation

plays in coastal dune formation and development by trapping

and stabilising windblown sands. It considers factors affecting

vegetation cover and condition, and morphology and physio-

logical traits of some plants. Finally, HE is related to human

processes that cause extensive ecological and geomorphological

alterations in coastal dunes: temporary factors (pedestrian and

vehicle trampling, horse riding, grazing, seasonal outdoor

facilities, presence of sea litter in the beach, and beach

Figure 2. Coastal segments (S1–13, E1–4) defined in the study as well as zones with low, medium, and high visitor pressure and level of accessibility in the

spit of El Rompido (a) and Enebrales de Punta Umbrıa (b). Coastal segments are coloured according to the vulnerability groups defined by cluster analyses

(see legend). Accesses are represented as lines and urban and tourist settlements are represented as black patches in both systems.

Dune Vulnerability and Tourism Pressure in Gulf of Cadiz (Spain) 245


cleaning) as well as permanent factors (road building, housing,

parking, agriculture, afforestation, etc.).

Partial vulnerability indices (VIp; i.e., GCD, MI, AI, VC, HE)

was calculated as the sum of the ranked variables (Vi) divided

by the sum of the maximum ranking attainable within each

group or partial index (Vp max):

VIp ~X

Vi

.XVp max

Total VI was calculated as the average of the five partial indices

(Garcıa Mora et al., 2001):

VI ~ GCDzMIzAIzVCzHEð Þ=5

Partial and total VIs can range from 0 to 1, and as the index

increases, the ability of a dune system to withstand further

impacts decreases. Results are presented graphically on a five-

axis figure, each axis corresponding to a partial index, so it is

easily appreciable the contribution of each partial index and

theassociated factors to total vulnerability. Linking partial

vulnerability values defines a polygon whose area is positively

correlated to the total VI values (see Figure 2.4) (Garcıa Mora

et al., 2001).

Field data were recorded in summer of 2004. To apply the

checklist, the coastal frame was previously divided into 17

homogeneous segments on the basis of sedimentary dynamics

(eroding/noneroding; direct observations during winter of 2003

and 2004) and ecological criteria such as vegetation coverand

vitality. The checklist was applied in those segments over a

representative 100-m shore stretch and partial and total

vulnerability indices were calculated for each segment.

To relate visitor pressure to subsequent results from

vulnerability assessment, the study area was previously

divided into three zones attending to visitor pressure on the

basis of the facilities of access, as accessibility and visitor

pressure are closely related in the studied frame. A zone with

high accessibility corresponded to the whole Enebrales de

Punta Umbrıa frame, a zone with medium accessibility

corresponded to the spit western sector, and a zone with low

accessibility corresponded to the rest of the spit (Figure 2).

Data Analyses

A matrix with the values of the 5 VIps in the 17 sampled

coastal segments was subjected to hierarchical cluster analysis

(Euclidean distance method) to group segments of similar

vulnerability characteristics. Analysis of variance (ANOVA)

and post hoc Tukey tests were applied to compare partial and

total vulnerability values in those groups defined by cluster

analysis. Such analyses were used to compare the vulnerability

in the three defined zones with different visitor pressure and

accessibility degree. Normality of variables were tested before

applying parametric tests. Statistical analyses were carried out

by PCOrd 5.0 and STATISTICA 6.0.

RESULTS

Total VI ranged from 0.24 to 0.55 in the studied segments

(Table 1). Geomorphology condition of the dune system partial

index showed the highest vulnerability values, being relatively

homogeneous along the whole studied coastal stretch. Marine

influence partial index showed also high values in segments in

the spit, with some variation. In Enebrales, the most occidental

segment (E1) showed the MI highest value, keeping lower and

similar values in the rest of segments. Comparatively, those

lower values were only reached by the highest MI values in the

spit (see Table 1). Aeolian influence and VC partial indices

obtained the most variable values, being in general higher in

those segments located in Enebrales, and showing quite low VC

values in the eastern sector in the spit. Human effect partial

index showed higher values in those segments located in the

western sector of the spit and in Enebrales, but lower values in

the rest of the spit.

Cluster analysis defined three main groups attending to

vulnerability values:

Table 1. Characteristics of segments defined in the spit of El Rompido (S) and Enebrales de Punta Umbrıa (E) active coastal frame, and obtained partial and

total vulnerability index values.

Segment Length (m) Sedimentary Dynamic Visitor Pressure GCD MI AI VC HE VI

S1 1398 ne Medium 0.53 0.48 0.48 0.49 0.63 0.52

S2 299 e Medium 0.69 0.53 0.45 0.35 0.46 0.50

S3 398 e Medium 0.56 0.50 0.44 0.45 0.57 0.50

S4 474 e Medium 0.44 0.60 0.43 0.48 0.32 0.45

S5 562 e Low 0.44 0.60 0.47 0.58 0.18 0.46

S6 522 ne Low 0.61 0.43 0.33 0.23 0.25 0.37

S7 358 e Low 0.67 0.70 0.43 0.58 0.11 0.49

S8 2424 ne Low 0.56 0.40 0.14 0.03 0.17 0.26

S9 875 e Low 0.67 0.60 0.35 0.45 0.08 0.43

S10 991 ne Low 0.61 0.45 0.05 0.03 0.11 0.25

S11 811 e Low 0.64 0.55 0.30 0.05 0.23 0.35

S12 1394 ne Low 0.56 0.35 0.13 0.03 0.13 0.24

S13 506 ne Low 0.72 0.48 0.22 0.03 0.13 0.32

E1 331 e High 0.64 0.65 0.45 0.53 0.51 0.55

E2 665 e High 0.64 0.53 0.38 0.30 0.55 0.48

E3 1352 e High 0.64 0.50 0.35 0.23 0.51 0.44

E4 560 e High 0.64 0.53 0.23 0.30 0.57 0.45

GCD 5 Geomorphology condition of the dune system, MI 5 marine influence, AI 5 aeolian influence;, VC 5 vegetation condition, HE 5 human effect, VI 5

total vulnerability index, e 5 eroding, ne 5 noneroding.



N Group I, low vulnerability: VI ranged from 0.24 to 0.37

(0.30 6 0.02, mean 6 standard error [SE]). This group

enclosed six segments located in the zone with low

accessibility (S6, S8, S10, S11, S12, and S13) (Figure 2a).

Vulnerability was determined by geomorphological and MI

features. Geomorphological condition of the dune system

and MI showed medium to high values, whereas AI, VC,

and HE had a low contribution to total vulnerability,

showing low and quite low values (Table 1, Figure 3).

N Group II, type I medium vulnerability: VI ranged from 0.43

to 0.49 (0.46 6 0.01, mean 6 SE). It enclosed four

segments, all of them in the spit and characterized by a

Figure 3. Graphic representation of vulnerability partial and total indices in the assessed segments. Figures are grouped into those three vulnerability

groups defined by cluster analysis.



negative sedimentary budget (Figure 2a). One segment

was located in the zone with medium accessibility (S4) and

three in the zone with low accessibility (S5, S7, and S9).

Vulnerability was mainly determined by physical (medium

and high GCD, MI, and AI values) and biological factors

(medium VC values) that are, to a great extent, inherent to

the system. Nevertheless, human pressure was less

important in these cases, which showed low HE values

(Table 1, Figure 3).

N Group III, type II medium vulnerability: VI ranged from

0.44 to 0.55 (0.49 6 0.01, mean 6 SE). This group enclosed

all segments located in Enebrales (E1, E2, E3, and E4),

corresponding to the zone with high accessibility and three

segments (S1, S2, and S3) located in the zone with medium

accessibility in the spit (Figure 2a,b). In these cases,

human influence was significant to total vulnerability,

together with geomorphological and marine features

(medium to high values of HE, GCD, and MI) (Table 1,

Figure 3).

Analysis of variance revealed statistically significantly lower

VI values in group I than in groups II and III (F 5 21.719, p ,

0.001), but no significant difference was found when comparing

those latter ones, both showing higher VI values. Analysis of

variance also found significant differences associated with

partial indices MI, AI, and VC when comparing groups I and II

(higher values in group II; p , 0.01) with partial MI, AI, VC,

and HE when comparing groups I and III (higher values in

group III; p , 0.05) and with partial HE when comparing

groups II and III (higher VC and lower HE values in group II; p

, 0.05). No difference was found for GCD in every case

(Table 2).

Analysis of variance revealed statistically significantly lower

VI values in the zone with low accessibility than in the zone

with high accessibility (F 5 6.715, p , 0.01). The zone with

medium accessibility showed intermediate values that were

not significantly different from those in the zones with low or

high accessibility. Human effect partial index showed signif-

icantly lower values in the zone with low accessibility in

comparison with zones with medium and high accessibility (F

5 45.702, p , 0.001), but no difference was found when

comparing those lateter ones. No difference was found for the

rest of partial indices in every case (Table 2).

DISCUSSION

Vulnerability status of the assessed segments, at local scale,

agreed with results obtained at regional scale by Garcıa Mora et

al. (2001), pointing out the appropriate functionality of this

assessment tool to different scales. Those low to medium

vulnerability values obtained in the study area (0.24 to 0.55,

into a theoretical range from 0 to 1) meant relatively medium to

high vulnerability status in the context of natural (not urban)

beaches in the Gulf of Cadiz at a regional scale (Garcıa Mora et

al., 2001). Furthermore, the application of checklists to this

local scale provided, in comparison with the regional assess-

ment, detailed results that were easily translated to specific

management actions.

Results showed higher vulnerability status related to two

different situations in the studied coastal frame: (i) segments

with a scarce sedimentary budget together with a high wind

and marine negative influence and a low stabilizing ability of

vegetation (segments with negative sedimentary budget in

zones with medium and low visitor pressure in the spit), and (ii)

segments subjected to a significant pressure of use, mainly due

to tourism in these particular cases (the most occidental

segments in the spit and the whole Enebrales stretch).

Vulnerability was strongly and homogeneously affected by

the geomorphological and sedimentary features in the whole

studied frame. Partial index GCD assesses the condition of the

basic structure of the system, upon which the rest of the factors

work. Observed high GCD values along the study area

indicated low sand sediment storage in the dune (Borrego,

Morales, and Pendon, 1993; Garcıa Mora et al., 2001). This

made both dune systems, spit of El Rompido and Enebrales de

Punta Umbrıa, less efficient to buffer destabilizing factors such

as storms, strong winds, or human impacts. Sea influence also

affected substantially the dune vulnerability status in the

assessed segments. Sea influence is identified as one of the

principal destabilizing factors to coastal dune systems (Brown

and McLachlan, 1990; Rodrıguez Ramırez et al., 2003),

particularly in those cases where vegetation cover is scarce or

nonexistent, so dunes are exposed to the direct incidence of

waves (Panario and Pineiro, 1997). Observed variations in MI

values were related to the spatial alternation of eroding and

noneroding segments in the spit of El Rompido, probably due to

small variations in the coastline in this case. In contrast,

Table 2. Mean values (6SE) of total and partial vulnerability indices calculated to each vulnerability group, defined by hierarchical cluster analysis

(roman), and to zones with low, medium, and high visitor pressure and accessibility level (italic).

Group I Group II Group III

Low

Accessibility Zone

Medium

Accessibility Zone

High

Accessibility Zone

Low

Vulnerability

Type I Medium

Vulnerability

Type II Medium

Vulnerability

IV 0.298 6 0.023***,{ 0.458 6 0.013***,{ 0.491 6 0.015***,{ 0.352 6 0.031*,{ 0.493 6 0.015*,{ 0.480 6 0.025*{IGD 0.617 6 0.024 0.555 6 0.066 0.620 6 0.021 0.610 6 0.027 0.555 6 0.052 0.640 6 0.000

IIM 0.443 6 0.028*,{ 0.625 6 0.025*,{ 0.531 6 0.021*{ 0.507 6 0.038 0.528 6 0.026 0.553 6 0.033

IIE 0.195 6 0.044**,{ 0.420 6 0.025**,{ 0.397 6 0.033**{ 0.269 6 0.048 0.450 6 0.011 0.353 6 0.046

ICV 0.067 6 0.033***,{ 0.523 6 0.034***,{ 0.379 6 0.042***{ 0.223 6 0.082 0.442 6 0.032 0.340 6 0.065

IPU 0.170 6 0.024***,{ 0.173 6 0.053***,{ 0.543 6 0.021***{ 0.154 6 0.019***,{,.a 0.495 6 0.068***,{ 0.535 6 0.015***,{

* p , 0.05, ** p , 0.01, *** p , 0.001.

{,{ Differences found by post hoc Tukey test between vulnerability groups or accessibility and visitor pressure zones.



Enebrales segments showed homogeneous orientation, more

exposed to the surf, that explained those relatively high and

uniform MI values. Higher MI values obtained in segment E1,

in comparison with the rest of the segments in Enebrales, could

be explained by the highest presence of man-made breaches

and washovers cutting the foredune in this segment, caused by

intense visitor trampling.

Wind impact was not relevant in the spit or Enebrales

segments when human impact was low or vegetation cover was

not particularly affected. Since vegetation acts to intercept and

stabilize sands transported by wind, characteristics of vegeta-

tion cover and wind impact are closely related factors in dune

ecosystems (Carter, 1988; Nordstrom, Lampe, and Vandemark,

2000; Ranwell, 1972). Vegetation cover acts to attenuate the

action of destabilizing forces such as storms and wind erosion

(Brown and McLachlan, 1990), playing an important role in

dune stabilization. On the other hand, human impact behaves

as one of the principal vegetation-limiting factors (Tsoar, 2001).

According to different works, high levels of trampling across

dunes cause soil compacting and loss of organic matter, directly

affects vegetal covering, and can alter species composition

(Andersen 1995a; Brown and McLachlan, 1990; Kutiel,

Zhevelev, and Harrison, 1999; Williams, Randerson, and

Sothern, 1997), leading to changes in vegetation status that

can negatively affect vegetation stabilizing ability (Garcıa

Mora, Gallego Fernandez, and Garcıa Novo, 2000; Williams et

al., 2001). In this sense, and independently from geomorpho-

logical condition of dunes, human impact can alter the natural

stabilization–destabilization balance (Brown and McLachlan,

1990; Psuty, 2004). To different authors, human impact acts as

an important destabilizing factor of dune systems, directly

related to the coastal dune instability and disorganization, as

well as to the loss of coastal dunes’ protecting role (Barrere,

1992; Nordstrom, Lampe, and Vandemark, 2000; Panario and

Pineiro, 1997; Psuty, 2004). Apart from its general role

affecting the vegetation condition, uncontrolled movement of

visitors throughout dunes to reach the beach in the studied

systems led to the creation of bare deflation breaches that cut

across and fragmented the foredune. These breaches mean

serious foredune morphological alterations that greatly con-

tribute to incremental negative effects of natural disturbances

such as wind and storms’ erosive action (Lemauviel and Roze,

2003; Munoz Valles, Gallego Fernandez, and Dellafiore, 2005).

In this context, significantly higher values of total vulnerability

(VI) and HE in segments included in the zone with higher

accessibility and visitor pressure (Enebrales) pointed out a

certain ineffectiveness of access structures in avoiding human

impact on the dune system. In comparison, segments included

in the zone with high accessibility (Enebrales), where there

exist six wooden walkways, showed similar VI and HE to those

included in the zone with medium accessibility (spit western

sector), where there was no wooden walkway at the study date

and visitors might walk across the foredune to reach the beach,

leading to the creation of numerous deflation breaches cutting

across the foredune. In the spit of El Rompido, the main access

to the beach, an asphalted road located at about 2 km from La

Antilla settlement (spit western sector), caused the larger of

these breaches. The path roaming behind the foredune

connecting La Antilla to this main access permits (and

sometimes guides) the uncontrolled walking of visitors

throughout the foredune, which leads to the formation and

development of numerous breaches homogeneously distributed

in this foredune strip, affecting the foredune integrity (Munoz

Valles, Gallego Fernandez, and Dellafiore, 2005). This ex-

plained the observed alteration degree in VC and foredune

morphology as well as the obtained VI and HE higher values. In

contrast, in Enebrales, those six wooden walkways ended

before reaching the beach, producing a fan effect (Brown and

McLachlan, 1990) that caused homogenous visitor distribution

as well as the creation of a high number of breaches in the

foredune.

Dune management and restoration plans applied during the

last several years make use of soft actions, not very aggressive

to the natural environment, aimed at removing or minimizing

factors that contribute to degradation and helping natural

processes recover by themselves (Gallego Fernandez, Garcıa

Mora, and Ley Vega de Seoane, 2003; Ley Vega de Seoane,

Gallego Fernandez, and Vidal Pascual, 2007; Pethick and

Crooks 2000). In these terms, and focusing management

strategies in the studied coastal frame, geomorphological and

sedimentary characteristics are intrinsic to the dune system

and they are not modifiable by soft actions that do not alter

the system or its surroundings. This fact makes management

difficult in those assessed segments where vulnerability was

due to this kind of factor (group II). Nevertheless, disturbance

caused by visitor pressure, in addition to being artificial, can

be avoided by soft management actions. To that effect, actions

focused on controlling and restoring human action in dunes

are necessary, particularly in those segments where vulner-

ability was due to this factor (group III). This kind of action

would be positive as well in those segments mainly affected by

other factors (i.e., group II) to minimize the destabilizing

action of human impact. In the case of group I (low

vulnerability status), access limitation was related to low

vulnerability values. In this case, conservation of the system

condition will depend on future uses developed upon the zone,

such as the types of use or the number and design of accesses.

Among other measures, correct design of accesses to the

coastal swimming zones becomes essential to focus manage-

ment to these coastal dune ecosystems. Access may be

constructed above the sand surface, respecting the dune and

foredune mobility and vegetation, from a zone outward from

the system to the open beach frame to respect the dune

system dynamics (Gallego Fernandez, Garcıa Mora, and Ley

Vega de Seoane, 2003; Ley Vega de Seoane, Gallego

Fernandez, and Vidal Pascual, 2007; Munoz Valles, Gallego

Fernandez, and Dellafiore, 2005).

CONCLUSIONS

Checklists and VI application to assess the vulnerability

status of dune systems at local scale was shown to be equally

efficient in identifying factors affecting vulnerability to the

more extended assessment at the regional scale. Furthermore,

the use of this tool at the local scale was more efficient in

designing specific management actions.

In the assessed dune systems, intrinsic characteristics such

as geomorphological and sedimentary features as well as MI



play an important role affecting the systems’ vulnerability

degree, but they are not modifiable by less aggressive soft

management actions. Human pressure, and particularly

pressure of people visiting dunes to reach the beach, meant

an important factor destabilizing both dune systems as well,

and this was mainly due to certain ineffectiveness of access

structures in restricting this influence in the dunes. In this

sense, future soft management actions might be focused in

correcting this fact in the assessed stretch.

ACKNOWLEDGMENTS

This work has been financed by the Spain Environmental

Ministry (Coast delegation). We thank the staff of the

Marismas del Odiel Natural Park for their help and support;

F. J. Cano, D. G. Sevilla, L. Zerpa, R. Gonzalez, and M.

Marquez for their help in the field; and R. F. LoFaso for her

help with translations.

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% RESUMEN %

La seria alteracion y progresiva perdida de dunas costeras durante las ultimas decadas ha desembocado en la peticion por parte de conservacionistas de evaluar el

estado de estos ecosistemas, habiendose desarrollado diversos ındices para evaluar la vulnerabilidad de los mismos. El estado de vulnerabilidad de dos sistemas

dunares protegidos, localizados en una zona central del Golfo de Cadiz (SO de la Penınsula Iberica), se ha evaluado a escala local y los resultados se han comparado

con los obtenidos en un estudio previo a escala regional. En 17 tramos de costa previamente definidos se ha calculado un ındice de vulnerabilidad (IV) basado en

variables que describen las caracterısticas geomorfologicas, la influencia del mar y el viento, el estado de la vegetacion y el impacto humano, identificandose los

principales factores que los afectan. Los valores de vulnerabilidad mas elevados se correspondieron con dos situaciones diferenciadas; tramos con un balance

sedimentario bajo o negativo y tramos sometidos a una considerable carga turıstica. El grado de vulnerabilidad de los tramos estudiados fue tambien analizado en

relacion a la presion de uso turıstico y el nivel de accesibilidad. El grado de vulnerabilidad de los tramos se relaciono directamente con las caracterısticas de los

accesos y la presion de visitantes, hallandose valores mayores de vulnerabilidad en aquellos tramos con mayor accesibilidad y afluencia de visitantes. Los resultados

obtenidos fueron mas detallados que aquellos de un estudio previo a escala regional, y fueron facilmente traducibles a acciones concretas de manejo. Estas acciones

deberıan estar enfocadas principalmente a controlar y limitar el impacto humano (turıstico), en especial en aquellos tramos seriamente afectados por este factor.



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