Cities as Ecosystems in the Emirates

Abstract

The United Arab Emirates (UAE) has had dramatic economic and population growth since its 1971 federation, with the built environment, green spaces, water features and other urban amenities growing to support its burgeoning population. These features, in turn, often provide unique habitats and microenvironments for a wide variety of resident and migratory species that benefit from their association with urban ecosystems, both on land and in nearshore coastal environments. While urbanization has undoubtedly caused important environmental challenges that should not be discounted, our growing cities have developed unique and important ecologies, much of which remains underappreciated and understudied in the UAE. Here we summarize the current understanding of urban ecology in the Emirates, providing insights into features that make cities amenable environments for organisms, particularly in the context of the UAE’s extreme environment. We also discuss several representative groups of organisms that benefit from the artificial environments provided by cities in both terrestrial and marine urban settings.

1 Recent Urban Growth in the Emirates

The total population of the United Arab Emirates (UAE) has grown from less than a 100,000 people in 1960 to just under 10 million by 2021 (Fig. 23.1). The most dramatic growth has occurred quite recently, with the population more than doubling since 2005. Today’s population is highly urban, with 88% of residents living in a city. As a result, there has been a dramatic expansion of urbanization across the nation to accommodate growing populations, with the built environment, green spaces, water amenities and other features of our cities serving as habitat for a wide variety of commensal species that benefit from the artificial environments and microclimates that our cities provide.

Fig. 23.1

Total population of the United Arab Emirates from 1960 to 2021. Graph data source: Population total, United Arab Emirates by the World Bank (CC BY-4.0)

As populations have expanded, so too has urban sprawl across the Emirates. Most of our urban spaces occur along the coastal fringe (Fig. 23.2), with the cities of Abu Dhabi, Dubai, Sharjah, Umm Al Quwain, Ras Al Khaimah and Fujairah, among others, growing from the much smaller early trading villages that developed in these areas due to their proximity to coastal resources such as fuel (mangroves) and fisheries. The only major exception is Al Ain, which grew from the oases and falaj-associated town that occurred at the base of Jebel Hafit. The dramatic expansion of the UAE’s cities, often merging laterally into one another along the Arabian Gulf coastline east of Abu Dhabi, and the country’s entire Gulf of Oman coastline, has led to urban habitats being the predominant ecosystem along much of the coastal fringe. Inland areas are bisected by vegetation-lined roadways, which in many cases follow traditional seasonal human migration routes, and consequently expand green habitat and act as corridors for the animals, plants and other organisms that have benefited from our presence.

Fig. 23.2

Population growth has resulted in concomitant expansion of urban areas across the UAE, particularly along coastal margins. This image, taken by an astronaut in the International Space Station on 11 Dec. 2013, illustrates the significance of urbanization across the Emirates. Image credit: NASA Photo ID ISS038-E-16335 courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center, under their conditions of use

In addition to expansion across terrestrial ecosystems, our cities have also expanded into the sea. Human-built infrastructure now dominates the seascapes of coastal cities, including structures such as seawalls, breakwaters, and piers, along with submarine pipelines and cables. Added to this are the semi-natural channels, beaches and intertidal areas created by coastal reclamation for real estate development (e.g. the ‘fronds’ of the Palm Jumeirah, among many others). While generally unrecognized by the public, such marine urban habitat occurs in incredible abundance. In the city of Dubai alone, over 200 km of artificial coastline has been created by dredging, with over 65 km of rocky breakwaters added for its protection, more than doubling the 90 km of natural coastline that had occurred here in the late 1990s (Fig. 23.3) (Burt et al. 2009b, 2012). While Dubai may be an extreme case, it is not an outlier; extensive addition of coastal infrastructure has occurred across much of the Emirates’ coastline. Offshore, the Arabian Gulf hosts over 2000 oil wellhead platforms that are connected by a network of thousands of kilometers of subsea pipelines (Stachowitsch et al. 2002). All of this infrastructure is rapidly colonized by marine organisms shortly after construction, and can develop highly diverse and abundant marine communities in just a few years as marine organisms co-opt our urban infrastructure into becoming large-scale artificial reefs (Burt et al. 2011, 2012; but see Sect. 23.2 below).

Fig. 23.3

The dramatic development of Dubai since the 1970s exemplifies the urban expansion across coastal fringes and into the sea occurring across the entire United Arab Emirates over the past half-century. Source: Fig. 2 in Burt (2014), reused with permission

Thus, UAE cities provide novel, varied and very recent ecosystems for organisms to exploit. While many species occurring in cities have reached them naturally, deliberate introductions and accidental escapes of non-native species—a phenomenon relatively frequent in urban areas globally but particularly marked in the cities of the Arabian Peninsula—have created unique assemblages of species in our urban areas. In addition to resident species, urban ecosystems also support transient species, particularly migratory birds and even marine animals such as the Whale Shark (Rhincodon typus), that stop off to feed and rest in urban marine habitats while en route to other parts of the world. Population densities of particularly successful urban species may be many times greater than those found naturally in the surrounding desert, despite many difficulties inherent in adapting to city life. These include direct dangers posed by traffic and predators such as feral cats, excessive noise and light pollution, and temperatures and humidity that often surpass those of adjacent natural habitats. Cities as ecosystems are also important as the only places where a large proportion of the human population regularly comes into contact with the natural world, where bold and conspicuous organisms may regularly come to one’s attention in a manner that is exceptional in natural habitats of the UAE. These may be anything from the Purple Sunbird (Cinnyris asiaticus) that squabble over flowering tobacco (Nicotiana sp.) plants on a balcony or weave an intricate hanging nest under roof eaves, to the Red Fox (Vulpes vulpes) or the Gazelle (Gazella arabica; Fig. 23.4) that are surprisingly tame on local golf courses. This chapter will showcase the cities of the UAE as ecosystems and discuss the challenges posed, opportunities provided, and the organisms that have taken advantage and thrived.

Fig. 23.4

Arabian Mountain Gazelle (Gazella arabica), part of herd that are well-established at a large golf course complex on the outskirts of Abu Dhabi. Photo credit: Oscar Campbell

2 Cities Are Not Surrogates for Natural Ecosystems

Urban expansion, of course, has not occurred without environmental challenges. Much of the fragile and unique coastal dune habitat of the UAE’s Arabian Gulf coast has now disappeared under our cities, threatening unique vegetation assemblages that occur only in these specific soil types (e.g. Panic Grass, Panicum turgidum), as well as associated habitat-specific biota (e.g. the critically endangered Wonder Gecko, Teratoscincus keyserlingii, Fig. 23.5) (see Chap. 5). Similarly, the east coast is now almost wholly dominated by urban sprawl, with natural habitat such as the now protected mangroves of Khor Kalba very much an exception. Specialist mammals reliant on particularly patchy resources, such as dugongs (Dugong dugong) and green turtles (Chelonia mydas) living in seagrass meadows, and large populations of breeding seabirds such as terns that are reliant on a small number of relatively undisturbed islands for nesting areas, are also negatively impacted by such development. Impacts can be direct or secondary, for example by increases in leisure activities such as boating, fishing and even by increased disturbance by beach visits from nearby urban populations, which represent a continuing and growing threat to turtle nests on UAE beaches (Whelan et al. 2019; Adhavan 2020). Our cities have also introduced light, noise and chemical pollution, disrupted hydrological cycles, favored the spread of non-native species, including feral predators such as cats and rats, and fragmented natural breeding populations, among other pressures. Our impacts in the sea have been equally destructive, if less visible. Coastal dredging and reclamation have resulted in incredible loss and degradation of some of the most biodiverse and productive ecosystems in the Emirates and the generation of new habitat by such processes in no way compensates for this. Further, sewage treatment, desalination and other industrial facilities continuously discharge into the shallow nearshore environments (Burt 2014; Le Quesne et al. 2021). As a whole, cities support a subset of ‘urban adaptable’ species, while suburban areas tend to favor species with life traits such as successional pioneer species or ‘edge’ specialists (McKinney 2006), all of which differ markedly from natural communities. Thankfully, in many cases some of the more destructive invasive species that have spread through UAE cities occur as urban specialists that seem unable to survive the extreme climate conditions prevailing in natural environments of the UAE. One example is the House Crow (Corvus splendens), a native of south Asia, which has remained a strictly coastal species in the UAE and is almost unknown both inland and from areas west of the Abu Dhabi capital. It does, however, readily travel to barren inshore islands that it would otherwise avoid to predate the eggs of nesting terns, and appears annually in spring in urban parks to seek out left-over food and the eggs and young of smaller birds such as doves, bulbuls and mynas.

Fig. 23.5

While urbanization can have ecological benefits, it also has costs. Urban expansion across the coastal dune systems of eastern Abu Dhabi and western Dubai have heavily impacted highly localized Panic Grass (Panicum turgidum) habitats, which are home to the critically endangered Wonder Gecko (Teratoscincus keyserlingii). Image credit: Andrew Gardner

While these issues should not be discounted in their importance, at the same time our growing cities have developed unique ecologies of their own, much of which remains underappreciated and understudied in the Emirates. In a climate as harsh as the UAE’s, for many species our urban habitats provide a refuge in which access to water, shade, unique microhabitats, and food resources allows populations to persist at far higher abundance than they could occur in natural habitats. Urban habitats have also resulted in the rapid development of interesting and indeed unique assemblages of species.

3 Cities as Amenable Environments for Organisms

Elsewhere in the world, cities are typically considered ‘urban heat islands’ as a result of the preponderance of radiative heating from glass, concrete, steel and related materials, waste heat from air conditioners and vehicle engines, and low evaporative cooling potential due to the dominance by impervious surfaces (Heisler and Brazel 2010). However, in arid areas the built environment can create a setting that favors far more benign conditions than in the surrounding desert.

The tall, vertical shapes of buildings, particularly around downtown cores and high-density areas, create conditions that favor wind funneling and shading that may be of benefit for urban-dwelling organisms (so called ‘street-canyons’; Pearlmutter et al. 1999), particularly during summer, and related design features are being actively incorporated into urban planning in the UAE for enhanced human comfort (Al-Sallal et al. 2001). Even in the absence of shading effects, buildings can reduce wind shear stress in their lee, and studies on desert plants have shown enhanced growth (in terms of height and biomass) compared with plants growing in exposed natural desert habitats (Bang et al. 2010). The stronger winds produced between buildings and the impervious surfaces of surrounding roadways can also act to enhance long-distance dispersal of seeds (Kowarik and von der Lippe 2011). In contrast, in areas that are dominated by impervious surfaces where bare soil is rare, adaptations can develop to enhance non-dispersal so that seeds remain on or near the soil patches where they originate, ensuring continuation of these urban populations and maintaining their diversity on vacant lots through time (Cheptou et al. 2008; Johnson et al. 2018). Thus, undeveloped plots in cities can represent important hotspots for vegetation growth (Fig. 23.6). The dynamic wind environment around buildings is also advantageously used by birds, who use building-induced updrafts and wind gradients to reduce energy expenditure during flight in urban settings (Shepard et al. 2016).

Fig. 23.6

Undeveloped land plots in desert cities can develop high-density plant assemblages. Here, Calotropis procera, Heliotropium kotschyi and Zygophyllum qatarense near the Sheikh Zayed road in Dubai. Such plants, being native to the UAE, likely also support diverse assemblages of invertebrates. Image credit: Gary Brown

Planted vegetation is an important feature of desert cities, which has been repeatedly shown to reduce urban temperatures relative to the surrounding arid environment because the evaporative cooling from plant transpiration causes temperatures within cities to be substantially lower than in surrounding landscapes (Lazzarini et al. 2014, 2015; Hall et al. 2016; Al-Ruzouq et al. 2022), including in the UAE (Frey et al. 2007; Issa and Saleous 2014; Mirou et al. 2022). At smaller scales, the presence of xerophilic (desert-adapted) trees can reduce temperatures at micro- to local-scales through shading (Wolf et al. 1996; Chow and Brazel 2012), allowing for distinctly cooler microenvironments for more mobile species to utilize. In the UAE such shading has been shown to provide a distinct advantage, where the Socotra Cormorant (Phalacrocorax nigrogularis) preferentially nest in the shade of planted trees (Fig. 23.7), and their offspring have significantly higher hatching success than those in unshaded areas (Muzaffar et al. 2012). Such shade-seeking is a common behavioral strategy used by a wide variety of arid-adapted animals to reduce thermal stress (Hetem et al. 2012; Newbold and MacMahon 2014; Roberts et al. 2016).

Fig. 23.7

Tree plantations around urban areas can reduce understory temperatures through shading. Here, Socotra Cormorants preferentially nest in the shade of planted Acacia trees in Umm Al Quwain, where hatching success is substantially higher than in the open. Image credit: Sabir Muzaffar

Urban water sources are also a critical feature that allows persistence of animals in desert cities. Access to urban water sources not only permits survival in an environment where freshwater is scarce to nonexistent, but also supports the greatly magnified water demand needed for evaporative cooling during the peak summer months (Riddell et al. 2019), and can reduce the metabolic costs of digestion compared to desert populations that do not have supplemental water available (Shochat et al. 2004).

Similar to terrestrial systems, the urbanization of marine systems can also provide opportunities for aquatic species. Coastal cities around the UAE are surrounded by relatively featureless bottoms comprised of sand and mud. By constructing submerged habitats made of rock, concrete and related materials, humans have dramatically increased the amount of hard-bottom habitat around coastal cities. This can have important implications for biodiversity, as many marine organisms are incapable of colonizing and growing on soft or mobile substrates. In Dubai, for example, where less than 10 km² of natural hard-bottom reef habitat occurred historically, over 65 linear kilometers of rocky substrates have been added in the form of defensive breakwaters (Burt et al. 2012), dramatically increasing the total available area that could be colonized by organisms such as corals, sponges, oysters and other fauna that are reliant on access to hard-bottom to growth. In addition, these structures provide a complex, three-dimensional habitat that is highly attractive to fishes (Fig. 23.8), providing shelter, foraging areas and spawning grounds in an environment that is largely flat, two-dimensional sand bottom (Burt et al. 2013). Such structures can also strongly affect the currents travelling along the coast, resulting in entrainment (i.e. pooling) and enhanced colonization by marine larvae that would most likely have been lost to offshore currents and predation had these structures not been in place (Burt et al. 2009a). Thus, marine infrastructure can play an important, although largely underappreciated, role in supporting biodiversity in the UAE (but see Burt (2014) for a discussion of the environmental costs of coastal development).

Fig. 23.8

Rocky breakwaters surrounding UAE coastal cities serve as an important habitat for fishes, many of which are attracted to the complex, three-dimensional structures, including (a) jacks (Carangoides bajad), (b) sergeant majors (Abudefduf vaigiensis), (c) painted sweetlips (Diagramma pictum), (d) two-bar seabream (Acanthopagrus bifasciatus), and (e) hammour (Epinephelus coioides). Photo credits: John Burt

3.1 Urban Green Spaces

Urban green spaces such as parks, private gardens, sports facilities and urban woodlands provide access to water, shade, complex three-dimensional microhabitats and food resources in desert cities, housing highly concentrated areas of biodiversity and interactive food webs in an arid environment typically supporting far fewer species. These green spaces are dense and highly productive due to water and nutrient enrichment, allowing the plants in these habitats to support far more extensive food webs than would be possible in less productive vegetation communities outside of cities. In addition to the introduced amenity plants that are typically included in these areas, urban green spaces can also act as refugia for native species. For example, Dubai’s Mushrif Park and the Mushrif Palace Gardens of Abu Dhabi act as de facto protected areas for woodlands of native ghaf (Prosopis cinerea) trees which can grow to their natural stature in the absence of the intense camel grazing that heavily impacts populations located outside of cities. Constructed ex-urban green spaces such as forestry and, particularly, agricultural areas, may be particularly significant for biodiversity in arid landscapes but are beyond the scope of this chapter (but see Chap. 15 for discussion of their importance more broadly).

In general, the floral composition of UAE cities is largely composed of non-native introduced species that create a completely new ecosystem, which is then colonized by a mix of native and non-native animal species. The proportion of non-native species is relatively high and the end-result is the formation of a completely distinct community. For example, of the 18 species of butterflies that occur in UAE urban areas, five (28%) are non-native (Feulner et al. 2021), while out of 36 regularly breeding bird species typical of urban areas, 14 (39%) are non-native (Pedersen et al. 2021). The prevalence of non-native organisms in urban areas in the UAE is in part due to supply, as humans have continuously introduced plants and animals to cities purposely (e.g. ornamental plants) and accidentally (e.g. domesticated cats that have gone feral), but also because of the environmental suitability of cities. The vast majority of non-native species are simply unable to survive in the arid, thermally hostile natural environment of the UAE (a factor labeled ‘environmental resistance’ in invasion ecology; Lovell et al. 2021), and therefore non-native species tend to concentrate in and expand throughout the more benign urban habitats that can support them. The reason many UAE native species have not proliferated to the same extent is likely down to their biology and interactions with other species. Most invasive non-native species are typically characterized by rapidly-reproducing, highly dispersive, generalist lifestyles that are highly amenable to urban settings (Kolar and Lodge 2001), while many native species may have far more restrictive habitat needs, lifestyles that limit their success in urban settings, and/or slower reproduction rates. In addition, species interactions likely also play a role. Invasive common mynas (Acridotheres tristis), house crows, rats and other commensal animals occur in urban environments in exceptional densities. Such species are generally highly aggressive and may out-compete and, in some cases, directly predate the eggs and young of other species; such characteristics are unusual in most native fauna, which ordinarily occur at much lower population densities in any case. Similarly, non-native plants likely ‘crowd out’ native species that may disperse seeds into urban green spaces, and the liberal use of herbicides and ‘weeding’ in managed greenspaces likely exacerbates issues for native plants establishing in these areas.

In urban parks native trees such as the delicately leaved, sweeping Ghaf are increasingly regarded as both culturally and environmentally significant and are widely planted. The Sidr Tree (Ziziphus spina-christii) is another native species that supports high biodiversity. For example, four species of native butterflies use one or the other as food-plants (Feulner et al. 2021). Such trees, although often planted at densities far beyond what is normal in natural environments in the UAE and causing a shaded and often very dry ground layer beneath, may often reach an older age, greater stature and much more luxuriant growth form than they are able to in wider countryside (Fig. 23.9). Again, this is attributable to the absence of severe grazing pressure that blights much of the UAE desert, although the inevitable over-zealous weeding, pruning and ‘tidying’ by the local municipalities generally has essentially the same effect. Another issue is over-watering, discouraging the formation of deep tap-roots; this may account for the overly severe damage suffered by many urban trees during the high winds encountered during occasional storms.

Fig. 23.9

The Verdant Ghaf (Prosopis cinerea; foreground) and the Toothbrush Tree, Salvadora persica; background) with lush growth in the absence of grazing in Abu Dhabi. Photo credit: Oscar Campbell

Thanks to the deliberate intervention of humans, soils are much richer and better developed in urban areas than virtually anywhere else in the UAE, and parameters such as humus (the organic component of soil) and nutrient content are much higher (Abdelfattah 2009; Abdelfattah et al. 2009). Such soils, and the non-native plants that are then grown in them, are responsible for the accidental introduction and subsequent establishment of many alien species and microbial pathogens into the UAE (Elsheikh et al. 2021). For example, the Soldier Orchid (Zeuxine strateumatica), a species native to south and east Asia, is believed to have reached the UAE (and many other parts of the world) thanks to importation of grass seed (Aspinall 2006). Populations of the Cycad Cupid (Chilades pandava), a small blue butterfly discovered in the UAE for the first time in Dubai in 2014, are completely restricted to association with the ornamental cycad Cycas revolute (Feulner et al. 2014). This invasive butterfly, native to south and southeast Asia has now reached Korea, Japan, Egypt and various islands in the Pacific and Indian Oceans, and is a severe pest of native cycads in many regions, although—as there are no such native cycads in Arabia—the butterfly’s persistence in the UAE is certainly reliant on horticulture. Similarly, widespread plantings of Mexican Petunia (Ruellia simplex), now a very common flowerbed shrub, have led to the establishment over a wide area of another butterfly, the Tiny Grass Blue (Zizula hylax; Feulner et al. 2021). Since its discovery in Dubai in 2016, it had broadened its distribution to Abu Dhabi, Al Ain and even Jebel Dhanna in the far west of the Emirates by 2021.

3.2 Urban Water Sources

As described earlier, water features are an important aspect of urban environments that help support biodiversity in desert cities. Fountains and related amenities are the most common freshwater sources in downtown cores, while swimming pools pepper the suburban landscape in areas where villas dominate, and these are widely used as drinking water sources by birds, feral mammals such as cats, and lizards. Often urban and suburban settings will also have small standing-water pools around leaking irrigation pipes, and these soon attract patrolling Slender Skimmers (Orthetrum sabina Fig. 23.10), one of the UAE’s commonest dragonflies and particularly tolerant of ephemeral and poor quality water. Birds often appreciate even the smallest drip in areas where water sources are uncommon, with Common Chiffchaffs (Phylloscopus collybita Fig. 23.11), a small over-wintering warbler particularly partial to such areas. Other standing water areas are ‘lake’ amenities in planned communities, which are most typically comprised of treated water from community sewage treatment plants and are typically brackish and nutrient-rich, supporting little other than algae. Aside from these planned and managed water features, unplanned ponds often develop where over-irrigation occurs in areas with shallow water tables. These often develop dense reed beds (mainly Phragmites) that can provide habitat for associated avifauna, although the water is typically brackish to saline and low in aquatic faunal diversity.

Fig. 23.10

Slender Skimmer (Orthetrum sabina), a common UAE dragonfly that is quick to appear at even ephemeral puddles. Photo credit: Oscar Campbell

Fig. 23.11

Common Chiffchaff (Phylloscopus collybita) attending a puddle created by a leaking irrigation pipe. Photo credit: Oscar Campbell

Box 23.1 The City That Never Sleeps: Urban Animals at Night

Fig. 23.12

Artificial light brightness in the UAE in 2015. Source: Data derived from Supplementary Data in Falchi et al. (2016) and shared under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

Artificial illumination is a defining phenomenon of urban development. In developed countries only the most remote areas are genuinely free of light pollution and the UAE is amongst the top twenty countries globally for artificial illumination, the extent of which is still increasing (Figs. 23.2 and 23.12) (Falchi et al. 2016). Such artificial light has profound implications for many organisms, particularly those that are nocturnally active.

Various species of marine turtles occur in the UAE, several of which utilize beaches to nest. Turtles hatchlings will typically use the ocean horizon, the brightest portion of the night sky in areas without light pollution, to orient after hatching so that they can reach the sea. As such, artificial lights adjacent to beaches have been implicated in disorienting hatchling migrations for nesting Olive Ridley turtles (Lepidochelys olivacea) on the UAE’s east coast (Yaghmour and Rodríguez-Zárate 2021), and light pollution management is being promoted for Hawksbill turtle (Eretmochelys imbricata) nesting sites on Arabian Gulf beaches (Grichting 2020).

Bats in urban environment are also particularly impacted by the development of artificial lights at night. Illumination changes their flight pattern and reduces their foraging activity, which suggests that lighting strongly reduces habitat availability and likely connectivity (Barré et al. 2021). Not all bat species are impacted in the same way, and some species show light tolerance, potentially shifting community composition (Seewagen and Adams 2021). Moreover, light can affect caterpillars’ development, reducing their abundance (Boyes et al. 2021), and as such prey availability for bats.

Light does not always have negative impacts, and can be used by visual species to expand their foraging opportunities. The effects of artificial illumination on birds has been relatively well-studied compared to many taxa, although work has concentrated on behavioral rather than physiological effects (Dominoni 2015). In the UAE, several shorebirds, including the locally common, breeding Black-winged Stilt (Himantopus himantopus) and Kentish Plover (Charadrius alexandrinus) regularly feed nocturnally on illuminated grasslands such as golf courses and even central reservations along busy city roads. Shorebirds, whose foraging cycles are generally tidal-dependent frequently feed nocturnally in natural intertidal habitats, but these species rarely use such urban grasslands diurnally. It is not clear if such habitats are favored at night due to reduced disturbance from people (or aggressive diurnal species such as House Crows) or if prey is more readily found at night. These two species are resident in the UAE but artificial light is known to have a direct and highly adverse impact on migratory birds (see Sect. 23.4).

4 An Overview of the Avifauna of Urban Areas

Green areas in cities, mainly parks, roadside verges and small plantations (sometimes comprising indigenous trees such as Ghaf but also gardens and golf courses hold very high densities of commensal bird species such as doves, bulbuls and House Sparrows (Passer domesticus). Non-natives such as bulbuls and parakeets are disproportionally well-represented in the avifauna urban areas throughout Arabia, with particular concentrations in the Abu Dhabi and Dubai (Jennings 2010) and both those and species with capacity to arrive independently (e.g. doves) have spread greatly with the general greening of the urban environment. Such areas provide oases of moisture and shade, often with abundant food. A number of species formerly restricted to montane areas or their environs, having reached urban areas under their own steam, have now adapted to city ecosystems and are as easy to find there as in their original natural habitats. These include Green Bee-eater (Merops orientalis) which relies on shallow banks of sand piles, readily found on construction sites, to excavate nesting holes and Indian Silverbill (Lonchura malabarica), a granivorous small finch that has adapted to forage on ornamental grasses such as Pennisetum. Pale Crag Martin (Ptyonoprogne obsoleta; Fig. 23.13), the UAE’s only regular breeding swallow, is now as at home nesting on buildings and under bridges as on rocky cliffs whilst Common Kestrels (Falco tinnuculus) and Pallid Swifts (Apus pallidus) have equally accepted large buildings as a suitable substitute for sea cliffs. The latter is a highly aerial species that lands only to nest, otherwise spending all its’ life on the wing. With a winter breeding season, they are present in the UAE from mid-autumn to late spring and the screaming hordes formed as they gather shortly before dusk make a wonderfully evocative spectacle over favored sites such as Dubai Museum. Their whereabouts from May to September remain a mystery. Figure 23.14 depicts four species that have benefit from new food sources and/or in urban ecosytems of the UAE. Several species (e.g. Eurasian Hoopoe Upupa epops and Indian Roller Coracias benghalensis) are common and conspicuous breeders in urban parks of the northern Emirates but extremely uncommon breeders on Abu Dhabi island and absent further west. Being mainly resident, the roller may still be in the process of very slowly spreading southwards but this is not true in the case of Eurasian Hoopoe, large numbers of which migrate through the entire country in spring and autumn. Instead, its general absence from seemingly suitable habitats in the western UAE may reflect subtle climatic variation. Increases in range and population are still on-going and may occur surprisingly suddenly. The most outstanding recent example is Northern Shikra (Accipiter badius), a small woodland-dwelling hawk first discovered in Dubai in 1996 and which soon became well-established there (Campbell 2018). However, it remained unknown away from the Greater Dubai area until 2013, since when it has spread spectacularly, with 498 records from 31 sites in 2019 alone (Campbell et al. 2022). Most of these sites are urban and include records from the entire span of the Arabian Gulf coastline from Sila’a on the Saudi border to the east coast and Al-Ain areas. The ultimate origins of the original Northern Shikra found in the UAE are subject to speculation (Campbell 2018), although no such doubt is associated with the Crested Honey-Buzzard (Pernis ptilorhynchus), a much larger raptorial species that breeds in south and east Asia and has steadily increased its numbers as a migrant and winter visitor to Arabia as a whole and the UAE in particular since the first record in 1992 (Babbington and Campbell 2016). A similar change of this species’ status in southern Israel has been linked to the spread of the introduced Dwarf Honey Bee (Apis florea) (Olsson et al. 2022), although the bee is native to the UAE, while the European Honey Bee (Apis mellifera) has flourished in urban areas in the UAE after its introduction for honey production. However not all species who rely on urban green areas in the UAE show a positive population trend. Eastern Olivaceous Warbler (Iduna pallida) is small, dull plumaged but vocal songbird that breeds in mature, shady plantations dominated by Ghaf trees on Abu Dhabi island only, where there is a small, dwindling resident population. It is otherwise very rare as an Arabian breeder (Jennings 2010) but occurs commonly as a migrant, as it breeds in central Asia and winters in tropical East Africa. Other species use urban areas to spend the winter, with, for example, dapper White Wagtails (Motacilla alba) arriving from early October onwards to any areas of grassland, especially if damp. Some winter visitors are even more conspicuous; Cattle Egrets (Bubulcus ibis) frequent central reservations and roundabouts and are regularly seen, and commented on, by the members of the general public as they wait at traffic lights. What is less appreciated is that these birds make daily flights to and from areas of mangroves where they roost in flocks of 50 or more (often using the same tree for many years) but additionally, in April, withdraw northwards to breed, presumably in Iran and southern Asia, before returning in September.

Fig. 23.13

Recently fledged juvenile Pale Crag Martins (Ptyonoprogne obsoleta). This species readily uses urban ledges as a substitute for traditional cliff nesting sites. Photo credit: Oscar Campbell

Fig. 23.14

Four species that have adapted well to urban environments in the UAE. Clockwise from top left, Pallid Swift (Apus pallidus), Crested Honey-Buzzard (Pernis ptilorhynchus), Northern Shikra (Accipiter badius), at nest in a Eucalyptus tree in urban Abu Dhabi and Indian Silverbill (Lonchura malabarica). Photo credits: Oscar Campbell

Finally, green areas in cities regularly provide life support, in the form of shade, water and food for many species of small migrant songbirds that battle through Arabia twice a year on migratory journeys spanning thousands of kilometers (see Chap. 15). Although representing a very small proportion of an urban site’s avian diversity or biomass at given time, these migrants greatly increase species diversity for a site as a whole; of the ten sites with the most diverse species lists in the UAE, three are wholly urban (eBird 2022). Migrations of the species involved are conducted mainly at night and it is likely that the now widespread and intense illumination of the UAE frequently causes disorientation and death of many migrants. This issue has come under increasing scrutiny elsewhere in the world (e.g. Loss et al. 2014) but is barely acknowledged as an issue, let alone studied, in Arabia. This is despite the region’s pre-eminence as a global stepping-stone for migratory birds.

5 Mammals in our Cities

Relatively few native mammal species have adapted to live in the urban environments of UAE. Most of these species are human-shy, highly adapted to live in arid habitats, and do not find favorable environmental conditions in our towns and cities. There are, however, a few exceptions, where species have found their way into the cities and—in some cases—even greatly benefited from urban habitats.

The Red Fox (Vulpes vulpes), a medium-size predator, is one of these native species that has adapted well to urban environments due to its dietary and behavioral plasticity. Worldwide, this widespread commensal species has colonized cities, finding food and shelter in parks and gardens, and reaching higher population densities than in its natural habitat. Mainly active at night, it is not rare to see them at dusk or dawn in the suburbs of all main UAE cities (Fig. 23.15), where they catch small animals or feed on food waste. The Ethiopian Hedgehog (Paraechinus aethiopicus), an insectivorous species that is widespread on the Arabian Peninsula and north of the Sahara in Africa, also frequents the parks and gardens of our cities. This species appears tolerant of habitat modification to a certain degree, and even in its natural habitat, generally prefers areas where food is more easily available, such as oasis and well-vegetated wadis. Green urban areas with enriched soils and an abundance of insects offer a good substitute to the often degraded natural habitats of the UAE. Al Ain, which has been occupied by human populations for several millennia and has extended its oases thanks to an ingenious underground irrigation system (falaj), has kept agricultural activities embedded in its urban development. This provides suitable conditions for Hedgehogs and other mammals, like bats.

Fig. 23.15

The Red Fox (Vulpes vulpes) is commonly observed in UAE cities. Image credit: Fouad Itani

The underground falaj system of Al Ain—Buraimi was known in the 1950s to shelter large populations of Trident Leaf-nosed Bat (Asellia tridens) and Persian Trident Bat (Triaenops persicus) (Harrison and Bates 1991), and these species may have occurred there for centuries. Although their populations have substantially decreased in recent years, both species are still present in the remains of falaj system, which were abandoned after they became dry in the past two decades due to the declining underground water table. Bats can often travel dozens of kilometers in one night between their roosting sites and foraging areas. Cities located in the vicinity of mountainous habitats, like Fujairah—half-surrounded by the Hajar Mountains—or Al Ain—at the foot of Jebel Hafit—attract more species of bats than the towns of the Arabian Gulf coast. The Muscat Mouse-tailed Bat (Rhinopoma muscatellum) often roosts in small caves or old buildings, and forage at night in the orchards and above the open green fields of Al Ain, Dibba and Fujairah (Judas et al. 2018). This is also the case of the Egyptian Fruit Bat (Rousettus aegyptiacus), that spends the day either in montane caves or in trees, and emerges to forage at night over city orchards or gardens. They also regularly drink water from urban artificial ponds and private swimming pools. The most common bat species in UAE cities is the ubiquitous Kuhl’s Pipistrelle (Pipistrellus kuhlii). This small bat, widespread around the Mediterranean basin in Arabia and West Asia, is encountered in all major towns where it roosts in colonies, sometimes of few hundred individuals. Tiny holes under the roof of buildings in well-vegetated compounds provide access to their roosts in the vicinity of foraging areas. Urban residents who may come across a colony in their home are often scared by their presence, more from lack of knowledge than any genuine threats. These animals are completely inoffensive, and are actually helping by predating on moths, mosquitoes or other pest insects. The Naked-rumped Tomb Bat (Taphozous nudiventris), who lives in rocky areas of the Emirates, is sometimes observed in old or under-construction buildings, but these are probably only temporary visitors from nearby natural habitats, than real urban inhabitants.

Native rodents, like the Arabian Spiny-mouse (Acomys dimidiatus), gerbils (Gerbillus spp.) and jirds (Meriones spp.) also prefer natural habitats to urban environments, and only venture to the edges of towns. During the strict quarantine period enforced at the beginning of the Covid-19 pandemic, cities became exceptionally quiet with virtually no traffic. Testimonies of wildlife entering cities came from all over the world. This also occurred in Dubai, where Sand Gazelles (Gazella marica) were seen walking peacefully on the highways in urbanized areas, showing that wildlife is never far and ready to quickly reconquer its lost habitats.

Beside the few native mammals that frequent UAE cities, four introduced non-native rodents are also ubiquitous in UAE urban environments. Mice (Mus musculus), the Brown Rat (Rattus norvegicus) and the Black Rat (Rattus rattus) are widespread species that often become pests, entering buildings and causing damage to food stores. These very adaptable species have followed human expansion for millennia and now provide food for predators that can also adapt to cities (Fig. 23.16). Urban domestic cats, feral cats and dogs are also very common in all UAE cities, and can have a high cost for urban wildlife, as documented in South Africa (Seymour et al. 2020). Feral dogs (Canis familiaris) live, forage and occasionally hunt in packs in parks, suburbs and landfills, often subsisting on food offerings from residents. Feral or domestic cats (Felis catus) are solitary animals that have retained the predatory hunting instinct of their ancestors, causing negative impacts on small urban fauna like reptiles, rodents, bats and birds. Feral Donkeys (Equus asinus), which lives mainly in the Hajar mountains, regularly venture in the suburbs of the east coast cities of Fujairah, Khor Fakkan, Kalba or Dibba. The Northern Palm Squirrel (Funambulus pennantii) has been introduced in UAE, first being noticed in agricultural areas of Ras-Al-Khaimah and Fujairah town in 2011 (Judas and Hellyer 2016). Since then, this very adaptable generalist species has invaded many urban parks across all UAE cities as well as agricultural areas. They do not appear to venture into natural habitats, suggesting that they will remain urban specialists in the UAE.

Fig. 23.16

Common Kestrel (Falco tinnuculus) with recently caught Brown Rat (Rattus norvegicus). Photo credit: Oscar Campbell

Cities comprise a complex assortment of habitat types, and we still know relatively little about the effects of their composition and spatial configuration on species distribution, and how these species respond to urbanization. Even species considered relatively common and well adapted to the urban landscape like Pipistrellus spp. may respond negatively to the built environment (Lintott et al. 2016). Mammals are exposed to multiple threats, noise, lights, sound and air pollution, as well as habitat changes (Finch et al. 2020), that may impact their feeding success. Effects of anthropogenic noise has deleterious effects on the foraging ecology of many animals, including bats (Song et al. 2020), although their effects can vary between species and situations. Noise can mask echolocation calls—due to frequency overlap—or create noise avoidance. In some cases, traffic noise has been shown to increase food intake of roosting bats, presumably as a response to stress and can induce metabolic dysregulation, immune disorders and disease. On the other hand, another study showed that noise affected bat activity and feeding behavior with a decrease of food intake in the proximity of the noise sources (Finch et al. 2020). Light at night can also affect foraging activities of nocturnal species. Since some species are more light tolerant than others, this can lead to shifts in community composition (Seewagen and Adams 2021). Road traffic also has an important toll on mammals, increasing road-kills in urban areas.

6 Cities Underwater: Importance of Submerged Infrastructure

Although knowledge of urban marine ecology in the Emirates remains underdeveloped, a series of research studies performed in the late 2000s, focused mainly on the coastal infrastructure of Dubai, has shed light on some general patterns. A study of large-scale rocky breakwaters across the emirate showed that they were rapidly colonized by corals (within two years) and that the coverage of the submerged rocks by coral grew relatively consistently over time (Fig. 23.17), such that by the time a breakwater was 20 years old it would typically have higher coverage by coral than is seen on natural coral reefs (Fig. 23.18), largely because these rocky breakwaters were elevated above the mobile sands that surround the low-lying reefs of Dubai (Burt et al. 2011). Fishes, because they are mobile, colonize these structures even more quickly from the surrounding environment. Surveys on the-then five year old Palm Jumeirah breakwater showed it to hold fish communities with diversity that was comparable to the natural coral reefs, and abundance that was significantly higher, presumably due to the complex three-dimensional structure provided by the breakwater (Burt et al. 2013).

Fig. 23.17

Rocky breakwaters are constructed to provide coastal defense for ports and marinas, but they also act as unintended artificial reefs. Juvenile corals colonize these structures within 1–2 years of construction (left) and grow laterally, developing three-dimensional complexity within 5 years (middle); they can eventually encrust most of the rocky substrate on decade or older breakwaters (right) if water quality conditions are favorable. Photo credits: John Burt

Fig. 23.18

Coral growth on UAE breakwaters over time. Corals typically colonize new breakwaters within a year or two after construction, with the total amount of coral increasing over decades. On mature breakwaters (more than 25 years) corals can cover nearly half of the available space on rocky breakwaters. Data from Fig 3e in Burt et al. (2011), reprinted with permission

Grizzle et al. (2016) conducted a nation-wide study to compare the abundance and diversity of coral communities on natural coral reefs and breakwaters. They showed that the highest species diversity observed at any location in the UAE was on the Saqr Port breakwater in Ras Al Khaimah, and that all other surveyed breakwaters had diversity comparable to or greater than on all coral reefs (Fig. 23.19, orange dots); they also showed that coral abundance was comparable to that seen on coral reefs (Fig. 23.19, green bars).

Fig. 23.19

The amount of coral (as percent coverage of the sea bottom, bars) and the total number of coral species observed (circles) on coral reefs (blue/red) and breakwaters (green/orange) across the UAE. The amount and number of species of coral on breakwaters are generally comparable, if not higher, than is observed on coral reefs, likely because they act as ‘walls’ for drifting coral larvae and because they are elevated above the mobile sands that typically surround natural reefs. Modified from Fig. 2 in Grizzle et al. (2016), reused with permission

While these observations are encouraging, it should be noted that such marine infrastructure cannot serve as surrogates for natural ecosystems. While species diversity and abundance may be high, the species composition of these communities, both in terms of the corals and the fishes, is highly distinct between breakwaters and coral reefs (Burt et al. 2009b, 2013), with many functional roles also operating differently between these systems (for example, higher abundance of predatory fishes on breakwaters) (Burt et al. 2013). As such, there has been a push against using ecological benefits of infrastructure for ‘greenwashing’ purposes to promote further development (Burt 2014), but rather to recognize infrastructure as important but unique systems. Further, ‘ecological engineering’ approaches—where knowledge of biology is factored into the design of marine infrastructure—are being promoted to further enhance the ecological value of any new developments that occur along our coastline (Burt and Bartholomew 2019).

7 Conclusion

There exists a great potential for the use of urban green spaces, either constructed (e.g. city parks) or natural (e.g. mangroves forests) for environmental education (Burt et al. 2019, 2021). This has the potential to both raise awareness of the importance and vulnerability of local ecosystems and habitats amongst the local populations, but also greatly enhance the quality of life of many city-dwelling residents. Many large urban centers of the UAE, including Abu Dhabi, Al Ain, Dubai and the city of Fujairah, are blessed with wonderful natural landscapes, and much more could be done to promote both the surrounding nature and the biodiversity of even the most mundane of urban green spaces.

Al-Wasit Reserve in Sharjah exemplifies bringing people and nature together in an urban setting; opportunities such as those presented by Ras al-Khor (Dubai) or Eastern Mangrove National Park (Abu Dhabi; Fig. 23.20) are still far from being fully realized. Simple signage, attractively designed and including informative highlights on a few common organisms and key ecological processes, could be provided for a very modest cost, yet are rare in the UAE, although such efforts are increasing. A deliberate policy of leaving even small areas of urban green space, including parks, relatively unmanaged (with information provided on why this is being done) could be enacted as a small but valuable gesture to increase awareness of ‘reclaiming nature’ by allowing natural successional processes to occur. A recent policy evident in the Western Region to plant selected roundabouts and verges with native herbs that are then allowed to flower and set seed, produces hotspots rich in biodiversity with greatly reduced water and maintenance demands than species that are more typically planted. Developments such as this, while small, are welcome and guide the way towards a more sustainable and publicly-engaged future for the Emirates.

Fig. 23.20

Mangrove forests represent an ecosystem where people can experience nature in cities, allowing opportunity for enhanced environmental awareness and education. Image credit: Jay Alonzo

8 Recommended Readings

Readers interested in learning more about the birds and mammals of UAE urban areas are recommended to seek out Aspinall (2005) and Hellyer and Aspinall (2005), respectively, with bats specifically described in Judas et al. (2018). For those interested in the marine ecology of urban infrastructure in the Emirates, Burt et al. (2012) provides a summary written towards the public, but the benefits of such ‘artificial reefs’ should be considered against the environmental costs that also come with undermanaged coastal development, which is discussed in detail in Burt (2014).