Proximity to urban fringe recreational facilities increases native biodiversity in an arid rangeland

Abstract

Urban developments affect neighbouring ecosystems in multiple ways, usually decreasing native biodiversity. Arabian arid rangeland was studied to identify the primary causes of biodiversity variation. Al Marmoum is a 990 km2 area on the urban edge of Dubai, designated for ecological ‘enhancement’ and outdoor recreational use. The area lacks historical biodiversity data but is thought to be primarily influenced by camel herbivory. Perennial floral and faunal diversity was assessed at 54 sites. Counts of reintroduced ungulates (Arabian Oryx, Arabian and Sand Gazelle) were made at 79 separate sites. Correlations of observed biodiversity with substrate type, anthropogenic structures, and ungulate distribution were assessed. Native biodiversity was substantially higher in north-northwest locations near recreational facilities, with the most likely cause being differential browsing pressure. Camel browsing faced greater communal regulation in the north-northwest, while oryx and gazelles congregated at feed points in the south-southeast that were farther from human activity. Arid rangeland in this socio-ecological landscape exhibits greater natural biodiversity at the urban fringe. Human activity reduces ungulate density, enabling a greater diversity of perennial flora which then attracts non-ungulate fauna. Anthropogenic features can therefore offer conservation value in landscapes where ungulate populations are artificially elevated.

Full text

Proximity to urban fringe recreational facilities increases native
biodiversity in an arid rangeland
Tamer Khafaga
A
, Greg Simkins
B
and David Gallacher
C,D
A
Universidad de Málaga, Avenida de la Estación de El Palo, 4, 29017 Málaga, Spain.
B
Dubai Desert Conservation Reserve, PO Box 191177, Dubai, United Arab Emirates.
C
Department of Interdisciplinary Studies, Zayed University, PO Box 19282, Al Ruwayyah, Dubai,
United Arab Emirates.
D
Corresponding author. Emails: david.gallacher@zu.ac.ae; david.gallacher.dr@gmail.com
Abstract. Urban developments affect neighbouring ecosystems in multiple ways, usually decreasing native biodiversity.
Arabian arid rangeland was studied to identify the primary causes of biodiversity variation. Al Marmoum is a 990 km
2
area
on the urban edge of Dubai, designated for ecological ‘enhancement’and outdoor recreational use. The area lacks historical
biodiversity data, but is thought to be primarily influenced by Arabian camel (Camelus dromedarius Linnaeus, 1758)
herbivory. Perennial floral and faunal diversity was assessed at 54 sites. Counts of reintroduced ungulates (Arabian oryx
Oryx leucoryx (Pallas, 1777), Arabian gazelle Gazella gazella cora (C.H. Smith, 1827) and sand gazelle G. subgutturosa
marica (Thomas, 1897)) were made at 79 separate sites. Correlations of observed biodiversity with substrate type,
anthropogenic structures, and ungulate distribution were assessed. Native biodiversity was substantially higher in north-
north-west locations near recreational facilities, with the most likely cause being differential browsing pressure. Camel
browsing faced greater communal regulation in the north-north-west, whereas oryx and gazelles congregated at feed points
in the south-south-east that were farther from human activity. Arid rangeland in this socioecological landscape exhibits
greater natural biodiversity at the urban fringe. Human activity reduces ungulate density, enabling a greater diversity of
perennial flora, which then attracts non-ungulate fauna. Anthropogenic features can therefore offer conservation value in
landscapes where ungulate populations are artificially elevated.
Additional keywords: anthropogenic, browsing, camel, herbivory, peri-urban, ungulate.
Received 1 May 2017, accepted 8 October 2018, published online 2 November 2018
Introduction
Urban fringes are normally associated with a reduction in native
biodiversity (Hansen et al.2005; Bekessy et al.2012), and
urban expansion is one of the leading causes of local extinctions
(Marzluff 2008). However, outer urban fringes sometimes
exhibit increased biodiversity, likely due to increased habitat
diversity that includes faunal access to resource-rich gardens
(McKinney 2002). Total phytomass may increase with groundwater
changes, which typically include an increase in both volume and
pollutants (Simon 2008). In such cases, the apparent ecological
health is controversial because the modified urban–rural
transitional landscapes favour immigrant species (Walker et al.
2009).
A healthy ecosystem of predominantly native species
has value beyond the preservation of natural heritage. High
biodiversity has a positive psychological effect (Carrus et al.
2015), and people are more connected with the natural
ecosystem of the region if that ecosystem reaches close to
their homes (McKinney 2006). Community participation is a
necessary component of long-term sustainability of conservation
efforts (Seddon 2000), but such participation may be problematic
in societies that retain a predominance of anthropocentric
over ecocentric values (Gagnon Thompson and Barton 1994).
Arabian camels (Camelus dromedarius Linnaeus, 1758) and
dates (Phoenix dactylifera L.) are held in high regard within
the Arabian culture, and edible species are held in higher regard
than species with little or no economic value (Seddon and Khoja
2003). Abu Dhabi Media Co. operates a television station
devoted to traditional sports, with camel racing as its primary
focus. Societies tend to conserve the species they value, to
the extent that the real environment often becomes a partial
reflection of social attitudes (Ouis 2003).
Camel herbivory is frequently cited as the main cause of
rangeland decline on the Arabian Peninsula (Batanouny 1990;
Assaeed 1997;Ferguson et al.1998; Abed and Hellyer 2001;
Hegazy and Lovett-Doust 2016). Camels have been present
for millennia (Peters 1997), but social, cultural and political
effects have resulted in a population explosion (Al-Rowaily
1999) since the end of the Second World War (Heady 1963).
Camel herbivory suppresses phytomass and reduces the proportion
Journal compilation Australian Rangeland Society 2018 www.publish.csiro.au/journals/trj
CSIRO PUBLISHING
The Rangeland Journal
https://doi.org/10.1071/RJ17041

of more palatable small perennial plants on all land surfaces,
but more severely on gravel substrate (Gallacher and Hill 2006).
Camel herder settlements are scattered throughout the Dubai
rangeland (Gallacher 2010), but camel densities are highest
around racetracks and are not directly associated with rangeland
provision of feed or water (Yagoub and Hobbs 2003). Land
tenure is not always clear and is traditionally based on water
access rather than geographical boundaries (Wilkinson 1983).
Land tenure in the bordering Abu Dhabi emirate is legally
defined (The General Secretariat of the Executive Council of
the Emirate of Abu Dhabi 2015), though enforcement is unclear
and the emirate boundary is porous. Rangeland access for
camel herders is thus regulated communally within Dubai
emirate, with few restrictions through unfenced rangeland or
across emirate boundaries.
In the present study, the ecological status of an arid rangeland
zone on the southern edge of Dubai emirate was assessed as
part of a proposal for extending an ecological recreation zone.
There appeared to be more plant growth in areas bordering
recreational facilities, and it was hypothesised that proximity
to an urban fringe recreational facility influences the biodiversity
of native faunal and floral species. Possible mechanisms for
increased biodiversity might include the provision of resources
(gardens, groundwater), the distribution of seeds, and the
suppression of browsing by livestock (camels) and native
ungulates (Arabian oryx Oryx leucoryx (Pallas, 1777), Arabian
gazelle Gazella gazella cora (C.H. Smith 1827) and sand
gazelle G. subgutturosa marica (Thomas, 1897)).
Materials and methods
Study site
Al Marmoum is a 990 km
2
open-access, protected area of
interspersed gravel plains and sand dunes on the inland fringe
of Dubai metropolitan area (Fig. 1). The area is hyper-arid, with
high summer temperatures, low rainfall of ~80 mm annually, and
lying in the humid coastal zone of the United Arab Emirates
(Böer 1997). Al Marmoum is bordered by the fenced 225 km
2
Dubai Desert Conservation Reserve (DDCR), a 62 km
2
fenced
military area, and the open-access arid rangelands of Abu Dhabi
emirate. Two unfenced, sealed roads cross the area, intersecting
perpendicularly. Camels and ungulates can move freely within
the United Arab Emirates, but cannot cross major roads or enter
fenced spaces such as the DDCR. Approximately 120 camel
enclosures are scattered throughout Al Marmoum. Enclosures
are comprised of one or more fenced areas, usually of ~200 m
2
each, and may include buildings. Information on the ownership
of camel enclosures in Dubai Emirate is lacking, though
Abu Dhabi
Dubai
N
0 2.25 4.5 9 13.5 18 Kilometers
Map produced by:
Legend
Random Survey Points
Ungulate sites
Habitats
Gravel Plains
Sand Dunes
Sand Stone
Main Roads
Secondary Roads
Desert Tracks
Cycle Tracks
Endurance Tracks
PowerLinks
DM Ghaf Plantations
Lake
Plantations
Fenced areas
Crop Land
Gravel Plains
Study area
Sharjah
AI Marmoom
Study area
Fig. 1. Map of the Al Marmoum open-access nature reserve, and its location within the United Arab Emirates (inset).
BThe Rangeland Journal T. Khafaga et al.

a general description of rangeland farms and livestock
enclosures has been published (Gallacher 2010). Camel diets
are only partially provided by rangeland, with the primary
source being provided within the enclosure from non-rangeland
sources. Hence, rangeland browsing pressure is strongly
influenced by animal husbandry practices and is significantly
lower than would be surmised from camel density estimates.
Several recreational facilities are provided within Al
Marmoum, with more being proposed. Currently available are:
*Dubai International Endurance City; includes soil-graded
equestrian circuits, the longest being 160 km, and 15 km
2
of
stables and other facilities for the Dubai Equestrian Club.
*Al Qudra Cycle Track; includes tarmac cycle circuits, the
longest being 100 km, and facilities for patrons (bicycle hire,
cafeteria, changing rooms).
*Al Qudra Lakes; includes 14 km
2
of irrigated forests and
lakes, developed for day trips and overnight camping. Forest
species are mostly indigenous, though the high tree density
and placement on gravel substrate do not mimic natural
systems. The 40 lakes contain a mix of native and introduced
fauna, with a notably large population of ducks. Note that the
singular term ‘Al Qudra Lake’refers confusingly to a separate,
older lake associated with the Bab Al Shams Resort.
*Bab Al Shams Desert Resort and Spa; a 113-room hotel with
a3km
2
footprint.
*The Dubai Camel Racing Club is located on the area’s
perimeter, with race tracks (the longest being 8 km) and
35 km
2
of stables and other facilities.
A further 6 km
2
is used for pivot-irrigated forage production
of Medicago sativa L., and 10 km
2
for the Mohammed bin
Rashid Al Maktoum Solar Park. The area encompasses three
archaeological sites, but there are currently no plans to open
these to tourism.
Herbivore populations are encouraged to reside in the area
via 67 fixed feeding points, at which hay, water and shade are
provided ad libitum, and camels are exclosed via razor wire at and
above 1.5 m. Translocation has established populations of three
native ungulate and one bird species. Details were unavailable
regarding dates, numbers and sources of translocations, but likely
began around 2005. Arabian gazelle and sand gazelle were likely
introduced from a mix of captive and wild populations, and
Arabian oryx from captive populations only. Chlamydotis
macqueenii (J.E. Gray, 1832), the Asian houbara bustard, have
been released annually from captive-bred populations as part of
an ongoing release program at locations throughout the United
Arab Emirates. There have been unofficial reports of houbara
breeding colonies within Al Marmoum.
Data collection
Fifty-four sites were selected randomly within the existing and
proposed extension areas of Al Marmoum, using XTools Pro
16.1 plugin for ArcGIS to ensure representative sampling of
gravel and sand substrates. Perennial floral and faunal counts
were made from 7 to 16 August 2016 within a circle of 50 m
radius. Ephemeral plant species were absent during data
collection, but their distribution is not affected by ungulate
herbivory (Gallacher and Hill 2008). Perennial floral counts were
made on five 10 10 m plots within the circle, including one
central, and one randomly selected within each quartile of
50 m radius. This sampling method is time efficient for
heterogeneously distributed sparse vegetation (McAuliffe
1990). Faunal counts of tracks, burrows, faeces, skeletons and
living individuals were made in the entire circle. Ungulates
and sighted individuals were classified to species, but other
artefacts were classified broadly (rodent, lizard, etc.). Vertebrates
comprised 93% of observations. Sites were further ranked
based on ground observations of the substrate and included
9 stable and 24 active dunes, 17 gravel and 3 sandy plains, and
1 sandstone site.
In addition to counts made at study sites, live ungulates
(Arabian oryx, Arabian and sand gazelles) were counted once
during August 2016 at each of the 67 fixed feed points,
9 forested locations where feed had been provided, and
elsewhere when observed.
Data analysis
The Shannon–Wiener, Simpson and Margalef indices were
calculated for floral and faunal observations at each of the 54
sites. The first two indices represent Types I and II diversity (Peet
1974), which are more sensitive to variation in abundant and
rare species respectively. The third is an estimate of actual
species richness from observed data. Inverse distance weighting
(IDW) was used to generate heat maps of the predicted diversity
throughout the study area. The relative importance of each
species was estimated using the importance value index (IVI),
in which relative density, frequency, abundance and cover are
given equal weighting (Curtis and McIntosh 1951). The IVI
provides a broader assessment of a species presence within a
community than single measures do (Shukla and Chandel 1989;
Sharma 2003).
Direct distances from each sample site were measured (using
Google Earth) to the closest anthropogenic fixture for several
categories (sealed road, graded dirt road, plantation and/or
lake, a feeding point, cycle track, equestrian track, overhead
power line, camel enclosures, and non-farm buildings). Camel
enclosures were identified using Google Earth imagery, and
ranged from itinerant, small, fenced areas with a structure
providing shade, to permanent buildings with gardens and
livestock pens. The number of camels was assumed to vary
substantially from farm to farm.
Results
Perennial floral diversity was considerably higher in the north-
north-west (Fig. 2a,b), where recreational facilities are located
(horse stables, equestrian and cycle tracks, resort facilities
and day/night camping areas), and was lower in the central
zone. Higher diversity on the southern edges of the reserve
bordered the township of Al Faqa and a worker accommodation/
industrial facility in Abu Dhabi emirate (24.67888N, 55.16318E),
though it was not consistently higher near the town of Murqquab
or a southern afforestation project (24.62458N, 55.40278E). All
plant species observed within sites were native. Faunal diversity
was also higher in the north-north-west and displayed greater
homogeneity than floral diversity, though this may be an artefact
of the sampling method. No evidence of non-native animal
species was detected.
Arid urban fringe biodiversity The Rangeland Journal C

Study Area
0
Low Diversity
High Diversity
0 2 4 8 12 16
0 1.75 3.5 7 10.5 14
Kilometers
Kilometers
Shannon Predicted Diversity
Study Area
0
Low Diversity
High Diversity
Shannon Predicted Diversity Study Area
0
Low Diversity
High Diversity
<VALUE>
Study Area
0
Low Diversity
High Diversity
simpsons
Study Area
0
1–14
15–47
48–82
83–96
97–126
127–140
141–166
167–187
Ungulates Predicted Distribution
N
S
WE
N
S
WE
N
S
WE
N
S
WE
N
S
WE
0 2 4 8 12 16
Kilometers
0 2 4 8 12 16
Kilometers
0 2 4 8 12 16
Kilometers
(a) Shannon-Wiener floral diversity (b) Simpson’s floral diversity
(c) Shannon-Wiener faunal diversity (d) Simpson’s faunal diversity
(e) Ungulate count distribution
Fig. 2. Inverse distance weighted heat maps for Types I and II floral (a,b) and faunal (c,d) diversity indices and for ungulate counts (Arabian oryx, sand
gazelles and Arabian gazelles; e) in the Al Marmoum open-access reserve.
DThe Rangeland Journal T. Khafaga et al.

0
0.5
1.0
1.5
2.0
Index
North-northwest South-southeast
Ungulate counts
Shannon-Wiene
r
Index
- Flora
- Flora
- Flora
- Fauna
- Fauna
- Fauna
Richness index
Simpson index
Fig. 3. Quadratic correlations for floral (solid lines) and faunal (dashed lines) diversity indices, and ungulate
counts (dot–dash lines; 8% of average count per site) along a gradient from the nor-north-west (north-north-
west) to the sou-south-east (south-south-east) of Al Marmoum reserve.
0.8 3.0
2.5
2.0
1.5
0.5
0
1.0
3.0
2.5
2.0
1.5
0.5
0
1.0
2.5
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.0
1.5
0.5
0
1.0
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Active dunes
Stable dunes
Gravel plains
Sandy plains
Sandstone
Active dunes
Stable dunes
Gravel plains
Sandy plains
Sandstone
Active dunes
Stable dunes
Gravel plains
Sandy plains
Sandstone
0
0
Simpson’s Index Shannon-Weiner
Index
Margalef’s Index
FloraFauna
Fig. 4. Box-and-whisker plots of diversity indices for each of the five vegetation types,
including stable (9) and active (24) dunes, sandy (3) and gravel (17) plains, and sandstone (1).
Arid urban fringe biodiversity The Rangeland Journal E

Table 1. Plant species observ ed among the five habitat types, with life form (Raunkiær 1934), Impor tance Value Index (IVI) and frequency (percentage of plots in which the species
was observe d)
Family Life form; Raunkiær plant IVI Frequency Habitats (number of sites)
Species life-form
1
(%) Sand
stone (1)
Gravel
plains (17)
Sandy
plains (3)
Stable
dunes (9)
Active
dunes (24)
Total habitat
number
Asclepiadaceae
Leptadenia pyrotechnica (Forsk.) Decne. Perennial shrub Ph 109 9  2
Boraginaceae
Arnebia hispidissima (Lehm.) DC. Annual herb Th 30 0.1  3
Heliotropium digynum (Forsk.)
Aschers. ex C. Christ.
Perennial shrublet Ch 11 6   3
Heliotropium bacciferum var. crispum
(Desf.) Sauvage and Vindt.
Perennial shrublet Ch 7 6  2
Moltkiopsis ciliata (Forsk.) I. M. Johnst. Perennial shrublet Ch 41 7  2
Capparaceae
Dipterygium glaucum Decne. Perennial shrublet Ch 10 2 1
Chenopodiaceae
Cornulaca monacantha Delile Perennial shrublet Ch 45 0.04  2
Cruciferae
Eremobium aegyptiacum (Spreng.) Asch. Annual herb Th 6 2 1
Farsetia linearis Decne. Perennial shrublet Ch 13 2 1
Cyperaceae
Cyperus conglomeratus Rottb. Perennial sedge Ge 153 65   5
Fabaceae
Crotalaria aegyptiaca Benth. Perennial shrublet Ch 5 2 1
Indigofera colutea (Burm.f.) Merr. Perennial shrublet Ch 52 17  4
Indigofera intricata Boiss. Perennial shrublet Ch 21 9  4
Prosopis cineraria (L.) Druce Perennial tree Ph 72 6 1
Fumariaceae
Limeum arabicum Friedrich Perennial shrublet Ch 47 30    4
Geraniaceae
Monsonia nivea (Decne.) Decne. ex Webb Perennial shrublet Ch 46 13 2
Poaceae
Centropodia forsskaolii (Vahl) Cope Perennial grass Th/He 25 0.2  4
Coelachyrum pierceii (Benth.) Bor Perennial grass He 42 0.04 1
Panicum turgidum Forssk. Perennial grass He 51 19 4
Pennisetum divisum (J.F.Gmel.) Perennial grass He 16 7  2
Stipagrostis plumosa (L.) Munro
ex T.Anderson
Perennial grass He 55 46   5
Rosaeceae
Neurada procumbens L. Annual herb Th 18 4  2
FThe Rangeland Journal T. Khafaga et al.

A total of 615 Arabian oryx, 1098 Arabian and 650 sand
gazelles were observed, mainly in areas that were distant from
anthropogenic features, other than a road near the southern
border (Fig. 2e). Numbers were higher in the central-west and
south-south-east, approximately the opposite of both floral and
faunal diversity (Fig. 3).
Biodiversity was higher in stable than on active dunes, and
on sandy than on gravel plains (Fig. 4). This represented an
observed site richness difference of 2.5 and 3.8 on active
dunes, to 7.0 and 10.3 on sandy plains, for plant species
and animal artefacts. Three of the 29 observed plant species
were ephemeral, despite the timing of the study in summer.
Correlation between floral and faunal diversity among sites
was low (R
2
= 0.075, 0.122 and 0.045 for the Simpson,
Shannon–Weiner and Margalef indices respectively), but
among habitat types was high (R
2
= 0.374, 0.728 and 0.945).
Cyperus conglomeratus Rottb. was the most widespread plant
species, with the highest IVI, frequency, and appearance
across all five substrates (Table 1). Zygophyllum simplex L. was
common on gravel and Fagonia indica Burm. fil. on sandy
substrates. Gazelle and rodent tracks were observed at many
active dune and gravel plain sites, and at all other sites.
Plant diversity was significantly higher within 1 km of tree
plantations and lakes (P<0.003 for all three indices) and within
2.5 km of major roads (P<0.006 for all three indices). However,
anthropogenic features are clustered in the north–north-west
along the east–west main road, which follows a gravel plain,
and correlations became insignificant when this was taken into
account. Proximity to feeding points and camel farms showed
no correlation with diversity measures.
Discussion
Native biodiversity was ~3-fold higher near established
anthropogenic facilities in the north, and somewhat higher near
some but not all communities in the south. Plant biodiversity is
low across the United Arab Emirates (Hegazy and Lovett-
Doust 2016), and observed diversity is lower in summer, when
ephemeral species are mostly present only in seed form. Some
perennial species of ecological significance in the area did not
appear in sampling, including Acacia ehrenbergiana Hayne
and Calotropis procera (Ait.) Ait. fil. Hence, the true plant
species richness may be higher than observed.
Historical data is unavailable to determine whether
biodiversity distribution pre-dates anthropogenic structures.
Location of anthropogenic structures has been influenced by
substrate and proximity to the coast, and is unlikely to have
also been significantly influenced by biodiversity. Camel and
horse stables, towns, and solar facilities are located on gravel
plains, whereas forage production and the desert resort are
located on stable dunes. Variation in community self-regulation
of camel browsing throughout Al Marmoum could have caused
the observed spatial variation in biodiversity. Camel herders in
the north suggested the south has been, and continues to be,
overgrazed by intraday Abu Dhabi–based herders.
Proximity to camel enclosures did not affect plant diversity
at the scale observed in this study, though we expect that a
specifically designed transect study would find differences at
smaller scales (tens of metres from enclosures). Moderate
Salvadoraceae
Chrozophora oblongifolia (Delile)
A.Juss. ex Spreng.
Perennial shrub Ch 8 2 1
Solanaceae
Lycium shawii Roem. and Schult. Perennial shrub Ph 9 2 1
Zygophyllaceae
Fagonia indica Burm. fil. Perennial shrublet Ch 121 37  4
Tetraena qatarensis (Hadidi) Beier and Thulin Perennial shrublet Ch 65 11 4
Tribulus macropterus var. arabicus
(Hosni) F. Al-Hemaid and Jacob Thomas
Perennial herb Ch 54 4  2
Tribulus pentandrus Forsk. Perennial herb Ch 15 15  2
Zygophyllum simplex L. Perennial herb Th/Ch 127 33 1
1
Ch Chamaephyte; Ge Geophyte; He Hemicryptophyte; Ph Phanerophyte; Th Therophyte.
Arid urban fringe biodiversity The Rangeland Journal G

browsing can sometimes increase plant diversity through the
reduction of dominant species, but heavy browsing typically
reduces the richness of palatable species (Holechek et al.2010).
Observations of increaser and decreaser plant species were
mixed. The palatable grasses Panicum turgidum Forssk. and
Pennisetum divisum (J.F.Gmel.) Henrard were found only in
the north-north-west, and the palatable tree Calligonum
comosum L’Hér was not observed during the study, indicating
heavier browsing in the central and south-south-east regions.
However Calotropis procera, known to flourish under heavy
camel browsing (Gallacher 2010), was also not observed,
perhaps due to the presence of gazelles. Distribution of the
sedge Cyperus conglomeratus followed a similar pattern to the
Shannon–Wiener floral diversity (Fig. 2a), despite being an
early recoloniser of stressed habitats.
This study found no correlation between study-site
biodiversity and proximity to feeding points, but oryx and gazelle
densities were negatively correlated with site biodiversity and
proximity to human activity. These ungulates had ad libitum
access to non-rangeland food, water and shade sources at feed
points throughout Al Marmoum. It therefore appears they
preferentially inhabited areas away from people, using feed
points as their primary food source, and browsing on rangeland
vegetation nearby. Diurnal movement patterns of oryx and
gazelles were disrupted by reliance on feed points that provided
all their needs (food, water and shade) at a single location. In the
neighbouring DDCR, oryx utilised feed points, whereas gazelles
preferred rangeland vegetation if available. Oryx tend to disperse
uniformly during daytime and night-time browsing hours and
regroup at sunrise and sunset (Gallacher 2015). Ungulate
densities likely far exceed historical levels, but their level of
dependence on rangeland vegetation has not been measured.
Differential browsing is the most likely cause of the observed
spatial variation in biodiversity, due to camel herders using
areas that are less communally regulated, and other ungulates
avoiding human activity. Nevertheless, several other factors
could be contributing, including changes to groundwater, seed
bank production and dispersal, and faunal consumption of
irrigated vegetation. Groundwater distribution in the United
Arab Emirates has been substantially modified over the last
few decades through increased extraction and added recharge
sources (Murad et al.2007).
Protection from large herbivores is available for plants
in many anthropogenic structures, some of which also have
increased water availability. These areas may be important for
seed bank recharge of palatable species. Plants can grow far
larger with protection, and thus produce far more seeds than
plants without protection. Seed dispersal might also be affected
by faunal visits to irrigated spaces, and to anthropogenic activity
throughout the reserve. Equestrian tracks are regularly graded,
and on- and off-road vehicles of all sizes move throughout the
reserve. Higher site biodiversity appeared to be more associated
with fenced irrigated spaces than unfenced irrigated forests,
which is indicative that seed bank recharge might be significant.
Conclusions
A primary cause of rangeland degradation in Arabia is
open-access livestock herbivory. Ungulates and herders tend to
avoid peri-urban rangeland. This study found native biodiversity
to be higher in arid rangeland that bordered Dubai urban
developments, compared with rangeland further inland. Whether
this represents an increase over historical levels or a reduced
decline, is not known. The likely mechanism is the influence
of anthropogenic fixtures on browsing pressure by camels, oryx
and gazelles. Within the study area, camel browsing faced greater
communal regulation in locations bordering anthropogenic
fixtures, whereas oryx and gazelles selectively avoided these
areas. Anthropogenic fixtures can therefore offer conservation
value in this landscape by reducing the impact of elevated
ungulate populations.
Conflicts of interest
The authors declare no conflicts of interest.
Acknowledgements
Many thanks to Dr Richard Hornby, Nautica Environmental Consultants,
for his thorough review of the manuscript.
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