Keywords

1 Coastal Lagoons (Khors)

The Arabic word khor refers to coastal lagoons, bays and inlets, as well as to seasonal terrestrial watercourses, and is thought to have origins in the Arabic word ḵawr meaning “a low land between two stretches of higher ground”. In the United Arab Emirates (UAE), khors are typically low-lying tidal lagoons that exist in various shapes and sizes along the coastline and in some areas have been modified by urban development in recent decades. These structurally complex and dynamic land-sea ecosystems are hotspots of ecological connectivity that support high biological diversity and generate ecosystem services and benefits that are crucial for sustaining human wellbeing.

Lagoons are shallow-water transitional environments located at the edge of the ocean, forming the front-line in responding to urbanization pressures and to climate change where rising sea level, heatwaves and storms challenge and shape lagoonal ecology. As such, coastal lagoons are defined as areas of relatively shallow water that have been partly or wholly enclosed from the sea by the formation of depositional barriers such as islands and spits (Bird 1994). Kjerfve (1994) defined three broad categories of coastal lagoons as: (1) choked lagoons with a single narrow inlet; (2) restricted lagoons with several inlets and good circulation; and (3) leaky lagoons with many inlets, wide channels and strong tidal and wind driven circulation and flushing). The most common lagoon type in UAE is the choked lagoons, however, the UAE has examples of each of the three types of coastal lagoon (see the Distribution section below).

All coastal lagoons in the UAE have formed as a result of rising sea level during the Holocene epoch (i.e., during the past ~11,700 years) where coastal barriers were built by marine erosion and depositional processes. This was followed by a period of sediment deposition on the landward side of barriers resulting in a localized drop in sea level (Schneider 1975). The influence of the sea on lagoonal form and function is determined largely by the size and depth of inlets (and by dredged channels), the tidal range and the prevailing direction of currents. In the UAE strong moisture-laden winds from the northwest (shamals) create waves that reshape the coastal barrier dunes and support growth of halophytes (salt-tolerant plants) on dune ridges (Chap. 4). When combined with spring tides; the winds can bring sediments onto tidal flats where cyanobacterial mats thrive. These highly dynamic and ever-changing hydrodynamic and wind driven processes create the dendritic networks of channels delivering and removing sediments, nutrients, and organisms throughout the lagoonal circulation system that is constantly in flux.

Unlike the adjacent open ocean, tidal mixing and salinity can vary dramatically within and between lagoons. Lagoonal plants and animals are adapted to the highly variable daily conditions (sea water inundation, salinity and day-night temperature changes), and can also tolerate seasonal extremes of natural physicochemical fluctuations, yet these organisms remain vulnerable to human impacts. The tidal regime is of critical importance to organisms living between the high and low water marks because they need to survive periods of inundation during high tide, and exposure to intense solar radiation and desiccation during low tide. The complex tidal regime and the associated circulation system of lagoons epitomizes a homeostatic, or self-regulating, process with feedback that maintains a dynamic equilibrium providing sufficient stability for life to thrive.

Coastal lagoons provide a geomorphological setting for wetlands to thrive, where halophytic plants trap and bind inorganic sediments and organic matter to enhance stability of the land barriers and shallow sediments. In the UAE, topography shaped by coral and oyster reefs, oceanic carbonate sedimentation and windblown materials (Evans et al. 1964) and the interplay with biotic elements have generated gradients in environmental conditions and mosaics of habitat patches within these systems. Coastal lagoons promote high marine primary productivity from seagrass, algae and cyanobacteria that thrive in the photic zone where light can penetrate through the water column to allow photosynthesis. The complex patterns of coastal lagoons can be observed from above, where the intricacies of the hydrological network, with both its wetlands and drylands, can be clearly seen (Fig. 8.1).

Fig. 8.1
Aerial view of Khor at Umm al Quwain, low tide on July 2, 2023, exhibits vast coastal area, barrier islands, inlets, channels, urban zones, and wetlands.

The entire khor at Umm al Quwain as seen from space showing barrier islands, inlets and channels (including dredged), constructed land, urban areas and extensive wetlands. Image captured at low tide on 2nd July 2023. Source: PlanetScope imagery © 2023 Planet Labs Inc. and shared under their Terms of Service for Education and Research

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In the UAE, inner lagoons are typically hypersaline environments with salinity that can exceed 60 PSU (compared with 36 PSU in normal oceanic water) and are characterized by containing large areas of halophytic (salt tolerant) plants and microorganisms in intertidal and supratidal areas (Mateos-Molina et al. 2020, 2021a). Above the high tide are extensive supralittoral salt-flats called coastal sabkha where the salinity of groundwater is many times greater than seawater (Schneider 1975). The primary drivers of hypersalinity in UAE lagoons are the arid conditions and high rates of evaporation, low freshwater inflow and limited exchange with oceanic waters experienced by coastal lagoons.

Coastal lagoons also export materials, nutrients and biota to oceanic waters, fuelling food webs beyond their borders. Where powerful ebb channel flows occur, depositional sand deltas are created on the seaward side of land barriers. These outward-draining flows also transport nutrient-rich waters from the inner lagoon system to the outer more nutrient-poor oceanic water creating ecologically important nutrient subsidies, with potential benefits to outlying ecosystems and offshore fisheries.

2 Distribution of the Different Types of Coastal Lagoon in the Emirates

Coastal lagoons constitute a common coastal environment, occupying 13% of coastal areas worldwide (Kjerfve 1994). In the Emirates, the coastal lagoons are far more common and occupy approximately 27% of the coastline. The intricate geomorphology expands the intertidal and supratidal area along both coasts of the UAE, primarily in the low-lying Arabian Gulf coast, but with Khor Kalba being a remaining notable example on the east coast (Figs. 8.2 and 8.3).

Fig. 8.2
6 photos marked on the map of the Abu Dhabi and Dubai lagoons are as follows. Khor al-Baghal of 210 kilometers squared, Khor al-Bazam of 2320 kilometers squared, Bul Syayeef of 636 kilometers squared, Khor Faridah of 248 kilometers squared, Khor Ghanada of 44.6 kilometers squared, and Ras al Khor of 11.9 kilometers squared.

Distribution of lagoons in the emirates of Abu Dhabi and Dubai. Map created using ESRI ArcGIS Pro 3.0

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Fig. 8.3
Map titled Northern Emirate Lagoons created with E S R I Arc G I S Pro 3.0. The map displays the locations and distribution of lagoons in the northern emirates, providing geographical insights into the regions water bodies.

Distribution of lagoons in the northern emirates. Map created using ESRI ArcGIS Pro 3.0

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All three geomorphological types of coastal lagoon described by Kjerfve (1994) exist in the UAE. In the southwest of the emirates, close to the town of Mirfa in Abu Dhabi, lies Khor al Bazam, a leaky lagoon, which includes several connections to the open sea, where strong winds from the north maintain a highly flushed system (Fig. 8.2). More restricted lagoons are present on both sides of Abu Dhabi city, with several ‘drumstick’ or ‘T’ shaped barrier islands (Fig. 8.3). These barrier islands form the ‘T’ structure seaward and perpendicular to the prominent wind direction (shamal) (see Chap. 3). These are characterised as low to moderate wave energy systems with fine-grained sediments and brackish lagoonal marshes.

Large wave-driven dune formations along the coast of the UAE result in numerous barrier lagoons associated with low-lying areas in the lee of the dunes and abundant sediment that often builds into intertidal islands and spits. Hence, the tails of the barrier islands frequently extend south away from the direction of the shamal winds, which transport sands back towards the lagoon and restrict circulation. The consequence of this process can be visualised on Halat Al Bahrani Island, in Khor Bul Syayeef in Abu Dhabi (Fig. 8.4).

Fig. 8.4
A satellite view of Halat Al Bahrani Island shaping a T in Khor Bul Syayeef, Abu Dhabi.

Halat Al Bahrani Island forming a T-shaped structure of the Khor Bul Syayeef, Abu Dhabi. Source: ESRI World Imagery basemap using 0.5 m WorldView-2 (Maxar) satellite imagery

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The Khor Faridah and Khor al-Baghal complex near the Abu Dhabi capital city is made up of approximately 400 km2 of coastal lagoons, split by several natural and artificial or modified barrier islands, including Saadiyat, Al Jubail and Zeraa islands, that form ‘T’ shaped structures perpendicular to the prevailing winds (Fig. 8.2). Further north, Khor Ghanada lagoon near the Dubai border is restricted to two main channels that distribute tidal waters into the mangrove-dominated ecosystem. Here, numerous artificial channels have been created, flushing out highly saline waters and promoting mangrove growth.

In the northern emirates (Fig. 8.3), the prevailing wind changes to be more oblique to the direction of the coast, resulting in lagoons that are often stretched wide, parallel to the coast, and exhibiting more restricted connection to the ocean (i.e., choked systems). Khor al-Beidah at Umm al Quwain is the largest (~127 km2) and remains one of the most undisturbed lagoons in the Northern Emirates. The dominant wind force has transported barrier island sands alongshore on Siniya Island, which has extended the sand-spit feature over 600 m along the coast between 1984 and 2020.

Because of their sheltered nature, most of the lagoons in the UAE have been modified or dredged to accommodate local ports and related infrastructure. Al Khan, Khalid (locally referred to as Al-Buhaira) and Al Mamzar are highly modified lagoons in Sharjah that are widely used for recreation and commercial boating. Notwithstanding these modifications, each coastal feature is orientated north-east, reflecting the effect of the dominant shamal wind direction from the NNW. This effect is further exaggerated further north along the coast, where there are a series of lagoons in Ras al-Khaimah including Khor al Rams, Julfar and Khor al Muzahmi (Fig. 8.3). These three lagoons form over 22.9 km2 of biodiverse wetlands that are highly valuable to the ecotourism and fisheries industries. This has been recognised by an area of Al Muzahmi that has been designated with reserve status to ensure its conservation. Khor al Rams consists of a large barrier island (known as the Saraya Islands) and extends over 7 km along the shore. Ras al Khor in Dubai is another lagoon which has been significantly modified by development. This choked lagoon once had a singular narrow connection with the sea, but was heavily modified by the dredging of the main creek and the then-new Rashid Port in the 1960s, followed by expanded dredging further into the Ras Al Khor area in later years (Köstem 2021); the khor has now been linked to the sea through the Jumeirah area with the dredging of the Business Bay through the 2010s (Hammad 2019).

3 Biodiversity in Coastal Lagoons

Coastal lagoons in the UAE are highly productive ecosystems that support rich biodiversity and provide important ecosystem services. These coastal lagoons have been identified as priority areas for conservation due to the presence of key coastal habitats for threatened and locally important species and their life cycles (for example, species that utilize them as nursery habitats before moving out to open sea) (Ben Lamine et al. 2020; Mateos-Molina et al. 2021a, b). Coastal habitat mapping on the UAE coast of the Arabian Gulf revealed the coexistence of multiple important habitat types (sabkha, halophytes, mangroves, seagrasses, saltmarshes, etc.) forming an interconnected mosaic of different intertidal and subtidal habitats in the coastal lagoons (Mateos-Molina et al. 2020, 2021b). The composition and spatial arrangement of habitat types, together with hydrology, influence the ecological connectivity among those habitats and their organisms in coastal lagoons. This ecological interplay creates unique seascapes where the value of the whole ecosystem is more than the sum of its individual habitat types (Fig. 8.5). For that reason, it is critical to understand these complex seascapes and their ecological functions as whole social-ecological systems in order to design effective conservation actions.

Fig. 8.5
Seascape of Umm Al Quwain coastal lagoon, featuring diverse habitats with dense mangrove forest, salt marsh stands, mudflats, and sabkha.

Seascape of Umm Al Quwain coastal lagoon with the presence of multiple habitats, including dense mangrove forest, saltmarsh stands, mudflats and sabkha. (Photo: Daniel Mateos-Molina)

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Coastal lagoons in the UAE are important areas for carbon sequestration, the process of capturing and storing ‘blue carbon’, where carbon captured by marine living organisms gets trapped in sediments, potentially reducing atmospheric carbon dioxide (Nellemann et al. 2010). Coastal lagoons contain a variety of habitats associated with carbon capture, including mangroves, seagrasses and saltmarshes, and also coastal sabkha and microbial mats that are common in the region (Schile et al. 2017, Schile-Beers et al. 2018; Alsumaiti and Shahid 2019). Field measurements from dominant coastal habitat types in the UAE indicate that microbial mats, which support no emergent vegetation, exhibit the second highest carbon storage values after mature mangroves (Schile et al. 2017). Saltmarsh, coastal sabkha and seagrass also function as important blue carbon stocks. Thus, the conservation value of these ecosystems extends beyond their high biodiversity to their importance to climate change mitigation, an important feature given the UAE’s 2050 carbon neutrality goals.

Unlike terrestrial environments that are limited to sequester carbon through photosynthesis, habitats in coastal lagoons can accumulate carbon by encouraging the deposition of carbon dioxide into sediments in coastal waters. Suspended sediment from land runoff and erosion elsewhere along the coast gets trapped along with dead plant biomass in coastal lagoon environments which makes them hotspots for carbon burial. Furthermore, a lack of oxygen in water results in slower decomposition of carbon, therefore promoting long term sequestration (Campbell et al. 2015).

The coastal zones of the United Arab Emirates and the greater Arabian Gulf are characterized by relatively high levels of productivity due to nutrients originating on land (Nezlin et al. 2007; Muzaffar et al. 2017a). This makes the coastal lagoons and inlets fertile feeding areas for large shoals of ‘forage’ fish such as anchovies, sardines, herrings and scads (Muzaffar et al. 2017a, b) and a variety of juvenile individuals of larger fish species such as trevallies and barracudas. Anchovies and sardines undertake migrations along the coastal areas, making them seasonally abundant at different times along the coast. Collectively these small forage fish serve as an important food for larger fish, sharks, dolphins and seabirds (Muzaffar et al. 2017b). Numerous threatened coastal and marine species such as green and hawksbill turtles, halavi guitarfish, greater flamingo, socotra cormorant (see Box 8.1), and greater spotted eagle among many others use this habitat as a feeding, breeding and/or roosting ground (Fig. 8.6) (Whelan et al. 2017, 2019; https://ebird.org). Lagoon ecosystems are also home to extremely thermally tolerant corals (Smith et al. 2017) and are important seascapes for birds (including many globally threatened migratory species), particularly for feeding, breeding and roosting (Muzaffar 2020; Ben Lamine et al. 2020).

Fig. 8.6
3 underwater photographs exhibit sea creatures.

Presence of threatened species in a coastal lagoon. (a) Black tip reef shark, (b) Halavi Guitarfish and (c) Green Turtles. (All photos: Daniel Mateos-Molina)

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Box 8.1 UAE Lagoons as Critical Habitat for Socotra Cormorant

Socotra Cormorants are classified as globally vulnerable and geographically restricted in their distribution, occurring only in the Arabian Gulf and the adjoining Gulf of Oman, extending into the Gulf of Aden (BirdLife International 2018; Muzaffar 2020). The largest and most well-studied colony within the Arabian Gulf breeds on Siniya Island in Umm Al Quwain Khor (Fig. 8.7). Up to 26,000–41,000 pairs have been estimated to nest on this island, with an annual presence of around 150,000–200,000 individuals (Muzaffar et al. 2017a). They form gregarious breeding colonies between August and January (Muzaffar et al. 2017a; Muzaffar 2020). For the rest of the year, they disperse throughout the Arabian Gulf.

Fig. 8.7
4 photographs depict groups of birds near the shore and flying over water body.

(a) A breeding colony of Socotra Cormorants (Phalacrocorax nigrogularis) showing adults (black) and chicks (white) on Siniya Island, Umm Al Quwain Khor; (b) an early morning congregation of adults and juveniles getting ready to fly off to fishing grounds; (c) a pre-departure ‘raft’ of cormorants; and (d) a feeding frenzy at one of the foraging sites. All photos: Sabir Muzaffar

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As the searing hot summer begins, vast flocks of Socotra Cormorants start arriving at the northern sand banks of Siniya Island (Muzaffar et al. 2017a; Muzaffar 2020). Initially, they roost on the islands while scoping out the terrain and assessing the nearby fish stocks. Thus, as the Socotra cormorants initiate nesting, they have a steady supply of forage fish in the nearby waters.

Every morning, many cormorants gather near the shoreline, flexing their wings and getting ready for a morning of fishing (Muzaffar et al. 2017b). Then, as if by some unknown signal, individuals start flying in large groups towards the fishing areas, sometimes as much as 40 km away from the colony. Eventually, both the adults and juveniles leave Siniya Island mostly making their way along the coastline west towards offshore islands.

The relative abundance of forage fish in coastal waters indicates a healthy, functioning marine ecosystem. Socotra Cormorant populations have declined overall in the Arabian Gulf, although they appear to have increased within the United Arab Emirates (Khan et al. 2018). Overfishing and development in the coastal zones threaten the complex food web that supports the cormorant populations (Muzaffar et al. 2017a, b; Muzaffar 2020). The establishment of coastal marine protected areas that protect coastal lagoons and surrounding shallow waters of these islands is urgent to ensure the preservation of marine biodiversity and healthy flourishing ecosystems.

4 Socio-cultural Importance of the Coastal Lagoons

Coastal lagoons provide numerous and diverse ecosystem services for society such as fisheries (e.g., commercial fish species), regulation and protection of coastlines from floods and storms, regulation of climate change and purification of water among many others (Basset et al. 2013; Lopes and Videira 2013; Newton et al. 2014, 2018) (Fig. 8.8). Coastal lagoons also support tourism and recreational activities such as recreational fishing and boating, leisure and water sports in the United Arab Emirates. In addition, the historical nature of humanity’s relationship with coastal lagoons places lagoons as important for societal, archaeological, and heritage values (Craig 2006; Lasserre 1979).

Fig. 8.8
A schematic presents regenerative and sustainable actions between coastal lagoons and species and society connected via environmental, economic, and social factors.

Coastal lagoons support important ecosystem services. Modified from Fig. 1 in Pittman et al. (2022) and reused under Creative Commons (CC-BY 4.0)

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Several archaeological sites of human settlements have been discovered around coastal lagoons in the Emirates demonstrating the socio-cultural value of these ecosystems. The findings at archaeological sites showcase the historic importance of lagoons in food security and livelihoods (Fig. 8.9). At the Kalba coastal lagoon on the east coast, mangrove wood from nearby Avicennia marina forests were burned in the fireplace, while small finds such as fish bones and molluscs were also identified. The site is thought to have had strategic importance in maritime trade (Schwall and Jasim 2020). At Jazirat Al Hamrah, Ras Al Khaimah, pottery shards originating from the western Mediterranean, Mesopotamia, and Indo-Pakistani borderlands reveal the presence of the lagoonal settlements for commercial maritime trade (Potts et al. 2003; Mutin 2012). At Khor Al Beidah, Umm Al Quwain, the Ed-Dur Site is one of the largest archaeological sites in the UAE, with settlements over several periods, including the Ubaid period (3800–6500 BC), Bronze Age, Stone Age, Iron Age, and Pre-Islamic periods (Carter and Philip 2010). In fact, the development of modern day Umm Al Quwain began when a tribe of people led by Sheikh Majid bin Rashid Al Mualla moved from Siniya Island in Khor Al Beidah to the mainland (Government of Umm Al Quwain 2015). Food waste such as discarded oyster shells and fish skeletons indicate that fishing took place within the lagoon itself, though some fishing (for example tuna), may have occurred outside of the lagoon (Charpentier and Méry 2008).

Fig. 8.9
2 photographs suggest human occupation in the coastal lagoons. In the left photo, there are skeletal remains accumulated over time. In the right photo, there are eel-like structures.

Traces of human occupation in coastal lagoons. (a) Dugong bone mound and (b) the rostra of animals and the skulls placed in anatomical position, aligned ribs in Siniya Island, Umm Al Quwain. Source: Méry et al. (2009), reproduced with permission (license: 5514780773472)

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More recently, lagoons may have been used as boat shelters for trade and pearling. For example, from the late thirteenth century Julfar al-Mataf in Ras Al Khaimah was fabled as a commercial trading centre but declined over time due to the continuous siltation of the lagoon that had previously formed the natural harbour. As a result, people relocated closer to what is modern-day Ras Al Khaimah (Velde 2012).

In the early 1900s, many villages subsisted on fishing and pearl-diving, and some lagoons became important areas for local inhabitants involved in these two professions. For example, Abu Dhabi’s Bateen village, which lies close to Khor Al Batin, was noted to have 50 pearl-diving boats to export pearls and import a variety of commodities, including rice and coffee (Lorimer 1908).

5 Human Impacts on Coastal Lagoons

UAE’s coastal lagoons have played an important role in supporting human settlements for centuries from small coastal trading towns and neolithic fishing communities (Lidour et al. 2021) to the modern cities of today (Chap. 22). Consequently, the human footprint on coastal lagoons is considerable and diverse. Coastal urbanization including construction of new islands, creation of small artificial coastal lagoons and modifications to the hydromorphology of existing lagoons through the dredging of new channels has accelerated the loss of some coastal habitats and species whilst benefiting others (Chap. 23; Burt 2014). The city seascapes have also changed the physical structure of the coastline with construction of seawalls, breakwaters, jetties, piers, marinas, ports and related infrastructure having replaced the softer shorelines (Chap. 23; Burt and Bartholomew 2019). In addition, sheltered lagoonal coastlines are prime real estate for residential developments and for locating critical urban infrastructure such as marine storage and transport facilities (ports, marinas, storage depots), desalination plants, sewage treatment works and marine transport.

Over the past several decades new channels have been dredged to allow safe and efficient navigation between lagoons and to the open ocean in many of the coastal lagoons across the UAE (Fig. 8.10). These channels have reduced the environmental differences between the open ocean and coastal lagoons (e.g., water temperature and salinity), and therefore could be argued to have made the lagoon environment more amenable to life.

Fig. 8.10
2 aerial views of the northern Khor Faridah lagoon in Abu Dhabi, exhibit natural features with minimal human impact in December 1984 and a dynamic transformation of the landscape over time in December 2020.

A portion of the northern Khor Faridah lagoon (Abu Dhabi) in (a) December 1984 and (b) 36 years later in December 2020 showing artificial channels, land creation and modifications, extensive urbanization, as well as expansion of wetland vegetation in 2020 (dark green areas). Source: Google Earth, based on Landsat/Copernicus imagery, reused per Google Terms of Service

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Some lagoons have become less hypersaline where dredging has deepened channels and widened inlets to the ocean resulting in increased tidal flushing with lower salinity sea water (~38‰). In some areas, increased flushing and lowering of salinity together with nutrient runoff from land is thought to have improved habitat suitability for grey mangroves (Avicennia marina) allowing the recent expansion of existing and newly planted mangroves in several UAEs lagoons since 1990 (Elmahdy et al. 2020). The densest mangroves typically grow between tidal channels and the edges of mudflats. The ecological characteristics including human uses of coastal lagoons influence the capacity of a lagoon for carbon sequestration and storage (i.e., blue carbon), the delivery of a range of other ecosystem services and the suitability of its habitats to support biodiversity.

However, dredging results in the suspension of sediments that can increase turbidity that reduces water quality for light-sensitive organisms such as seagrasses and corals (Erftemeijer and Shuail 2012; Duck and da Silva 2012). Subsequently, there are consequences for species that rely on these habitats to survive (e.g., turtles). Dredging also results in increased water flow that can reduce soil stability for seagrass and mangrove seedling growth.

However, the changes to channel depth and complexity can benefit some highly mobile species. For example, research in Australia (Borland et al. 2022) found that functional diversity in fish assemblages was highest in urban estuaries where dredged channels were small (i.e. <1% of the estuary) and where channel slope orientation promoted light penetration to the seafloor. For most lagoons globally, however, our understanding of the direct and long-term indirect ecological consequences of channel modifications through dredging is insufficient to support effective ecosystem-based management, and this topic has yet to be well studied in the Emirates.

5.1 Marine Vessel Traffic

Marine vessels have multiple types of impact on marine environments that include underwater noise known to disturb marine animals, the potential for chemical pollution, the erosion of channel banks from bow-waves, collisions with the seabed (e.g. propellor scars in seagrass and groundings), and collisions with large air-breathing marine animals (turtles, dugongs and cetaceans) (Duarte et al. 2021). Marine vessels are a widespread and chronic source of underwater noise pollution. The underwater sound from vessels propagates over great distances (Fig. 8.11). As a result, vessels have altered marine soundscapes with high traffic areas suffering from chronic exposure to noise, especially in surrounding urban areas. Vessel noise overlaps with the audible frequencies of many marine mammals, turtles, fish and some invertebrates which can disrupt their orientation, communication, socializing, predator avoidance, settlement cues and rest. Therefore, a reduction in vessel noise can reduce cumulative pressure on marine species (Merchant 2019). In addition, in shallow water, vessel wakes disturb sediments leading to sediment resuspension and redistribution particularly where unvegetated soft sediments exist, such as lagoon channel banks. Wakes can propagate far into shallow-water areas, creating turbulence and erosion that increase turbidity and reduce water quality for plants and injure or displace juvenile fish (Zaggia et al. 2017).

Fig. 8.11
A screenshot of the global fishing watch screen exhibits the Khor Faridah lagoon and its vessel presence ranging from 0 to less than or equal to 2000 in hours per 0.5 kilometer squared.

Vessel traffic intensity within the Khor Faridah lagoon recorded using vessel locations/hours from the Automatic Identification System during a 2-year period (January 2018 to January 2020). The presence of a vessel is determined by taking one position per day per vessel from the positions transmitted by the vessel’s AIS. Only large vessels are required to use AIS. Source: Global Fishing Watch shared under Creative Commons license (CC BY 4.0)

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Vessel impact abatement policies and regulations are crucial for limiting their disturbance to lagoonal ecosystem. Vessel speeds and routes can be controlled to reduce impacts in biologically sensitive areas, solar-electric recreational boats and passenger ferries can be incentivised, and safe boating practices can be promoted to minimise collisions. Furthermore, technological solutions to vessel design and schemes can reduce impacts and infrastructural standards, such as green marina schemes, low impact moorings and initiatives to reduce waste disposal and chemical pollution.

5.2 Urban Light Pollution

Urbanization of coastal lagoons increases light pollution from streetlights, building and ports, altering the natural regime of night-time sky brightness. Artificial night lights impact a wide range of organisms including marine species in shallow water, insects and birds by disrupting fundamental processes such as circadian rhythms, energetics, movement orientation, reproduction and predator-prey relationships (Davies et al. 2014). The reported impacts, including disruption to molecular and cellular processes, are most severe for nocturnally active animals (Tidau et al. 2021). Light-induced mortality occurs with seabirds. White LEDs are now widely used as an energy efficient light source, but many marine organisms are sensitive to the short wavelengths they emit (Tamir et al. 2017).

Light-related impacts can be mitigated by changing the light source to a less biologically responsive wavelength or using barriers to reduce light spillage (i.e., from white to amber LED, filtered and shielded light sources) (Longcore et al. 2018). For example, The State of Florida prohibits lighting for new construction near beaches to emit wavelengths less than 560 nm to protect sea turtles. These changes are required if we are to transition to nature-positive urban environments that allow other species to coexist with us in the urban seascape. Comparison of urban night-light intensity measured by the VIIRS satellite (Visible Infrared Imaging Radiometer Suite—Day/Night Band DNB) (lightpollutionmap.info) revealed that night time irradiance across Umm al Quwain lagoon fluctuated between 2012 and 2017 and then increased by >40% from 2017 to 2022 (Fig. 8.12). A deeper scientific understanding of horizontal irradiance and the biological impacts of artificial lights on coastal lagoons needs to be conducted in collaboration with energy companies and urban municipalities.

Fig. 8.12
2 maps exhibit the data to understand the amount of artificial light in different parts of the world. Some areas exhibit brighter spots concluding more lights on that place while some appear dark that means there are fewer lights.

Artificial light at night (vertical radiance) measured from 2012 by the Visible and Infrared Imaging Suite (VIIRS) sensor on board NASA Joint Polar-Orbiting Satellites. Source: Data derived from NASA’s VIIRS/NPP Lunar BRDF-Adjusted Nighttime Lights Yearly composites and shared under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC)

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5.3 Water Pollution

Coastal lagoon waters and sediment quality are susceptible to contaminants and nutrients due to runoff from land, outflows of wastewater, and seepage from ground water that often occurs in urban and agricultural areas. This problem is further exacerbated by low flushing, sheltered waters and abundant depositional environments. Low rainfall in the UAE reduces the occurrence of land-based sources of pollution entering the marine waters, although the limited freshwater input also means flushing is entirely tidally driven. Water and sediment samples in UAE lagoons and urban creeks have been shown to have exceedances with some sediment-associated heavy metals (e.g., manganese, zinc, copper) (Shriadah 1998; Samara et al. 2020) and through bioaccumulation in fish (Cunningham et al. 2019). Little is known about the scale of the threat from engineered products such as discarded fishing gear and other sources of marine plastics, but as a global problem it must be considered as a priority in the management towards healthy coastal lagoons (Stöfen-O’Brien et al. 2022).

5.4 Implications of Climate Change for UAE Lagoons

Global climate change caused by greenhouse gas emissions are predicted to produce even more extreme conditions (e.g., higher salinities, higher temperatures, lower oxygen levels) in UAE’s coastal lagoons.

The Arabian Gulf holds the world’s warmest ocean water. Thermal expansion of the oceans and melting polar ice due to accelerated global warming are increasing sea levels, and this is projected to continue for centuries and potentially drive intertidal and shallow water species and habitats inland seeking more favourable conditions (Lauchlan and Nagelkerken 2020). IPCC projections of global mean SLR by 2100 range from 0.61 to 1.10 m (RCP 8.5) with some models predicting scenarios of over 2 m by 2100 due to large uncertainties in the stability of Greenland and Antarctic ice sheets (IPCC 2019). For the north-western Arabian Gulf, tidal gauge data indicated a relative sea-level rise of 2.2 ± 0.5 mm per year between 1979 and 2007 (Alothman et al. 2014) and publicly available coastal inundation maps for 2050 using moderate projections suggest that considerable changes in the intertidal habitats will occur (Melville-Rea et al. 2021; https://www.climatecentral.org/).

Submergence of 20–78% of coastal wetlands globally has been predicted to occur by 2100 while, simultaneously, some intertidal habitats may keep pace with sea level rise and expand landward (Spencer et al. 2016). Where hard barriers to landward shifts occur, such as seawalls and elevated relief, the phenomenon of ‘coastal squeeze’ will result in temporary loss of habitat (Mills et al. 2016). Efforts to conserve and expand natural intertidal habitats will serve to buffer the coastline from waves and inundation. As sea level rises, increasing wave action will erode low-lying sandy beaches and barrier islands that allowed lagoons to form, and creeks will begin to silt up and become more homogeneous as they transform into subtidal flats. On the landward edge, sea level rise may increase seawater intrusion into groundwater, reducing the inflow of freshwater to the lagoons and reducing the suitability of water for vegetation (Tully et al. 2019). Potential evapotranspiration has been predicted (SSP2–4.5) to increase throughout the region by up to 0.37 mm per year during the middle of the twenty-first century (2021–2050), likely creating harsher hyper-arid conditions and hyper-salinity for many coastal plants and animals (Ajjur and Al-Ghamdi 2021). Models based on RCP 8.5 scenario predict local extinctions of marine species due to decline in habitat suitability and a > 40% drop in potential fisheries production in UAE waters by 2090 (Wabnitz et al. 2018), although such estimates may be underestimated as the models did not include other human impacts or hard-to-predict processes such as predator-prey interactions. Organisms such as oysters, a wide range of shallow water sedentary species, and vulnerable juvenile fishes are expected to suffer from prolonged exposure to elevated temperatures, deoxygenation and acidification (i.e., ocean water becoming less alkaline and hindering calcification) (Weatherdon et al. 2016). Such changes are likely to have cascading effects through the lagoonal food web impacting birds and the food availability for marine fauna (Lincoln et al. 2021). These changes may allow ecological space for non-native species to become invasive nuisance species (e.g., some phytoplankton) while others will decline in threat (Clarke et al. 2020).

Impacts to lagoonal ecosystems from human activity are likely to have cumulative and unanticipated interactions accruing across scales in time and varying in space across the lagoons. The high biodiversity, diverse ecosystem services and vulnerability of coastal lagoons to climate change suggest that these fascinating formations can serve as priority locations for nature-based solutions (e.g., protection, climate adaptation, restoration) (Pittman et al. 2022). Considerable knowledge gaps exist in our understanding of how multiple interacting local and global stressors will influence species and habitats and the structure and function of the lagoons in the region (Melville-Rea et al. 2021). Strengthening relationships for data diplomacy, data sharing and collaboration among scientists of the region could facilitate accelerating our understanding of the impact of stressors in the UAE and the Gulf (Fawzi et al. 2022) Ecoengineering solutions and identifying areas for managed retreat will be important adaptation strategies with potential to increase coastal wetland area (Burt and Bartholomew 2019; Schuerch et al. 2018). It is clear that the structure and function of UAEs lagoons are profoundly intertwined with human activity.

6 Management and Conservation

The specific characteristics and spatial arrangement of coastal lagoons, where individual habitat types often intermingle with each other in a configuration of ‘seascape’ mosaics, point to the need for a whole-site and ecosystem-based approach for conservation and management. Such an integrated approach focuses on the integrity of the interconnected ecosystems, rather than individual habitat types, and focused on the ecological functioning and resilience of an area to maintain biodiversity and the flow and quality of ecosystem services. Considering the vulnerability of the coastal seascapes to human pressures, ecosystem-based management can strengthen the synergies between ecological and biodiversity conservation with key socio-economic challenges and needs.

To address the Kunming-Montreal Global Biodiversity Framework (GBF) targets that include 30% of land-sea protection by 2030 (CBD 2022), future plans to expand the current protected areas in the UAE can draw from the recommendations of local scientific studies, as well as global guidance by IUCN and the Convention of Biological diversity (CBD) calling for a science-based design of ecologically representative and interconnected protected area networks (i.e., Aichi Target 11). Following the definition on Areas of Particular Importance for Biodiversity (APIBs) by CBD, a recent study in the UAE identified a number of coastal lagoons as Marine ‘APIBs’ considering habitat richness and their critical role in different life-stages of endangered species, among other criteria (Ben Lamine et al. 2020). These Marine APIBs are underrepresented within the existing UAE national designation of Marine Protected Areas (MPAs) with an estimated gap between current and desired protection of approximately 78% (Ben Lamine et al. 2020). Continual coastal development and ecosystem fragmentation points to the urgent need to expand the extent of protection in the coastal and intertidal zones along the UAE’s waters and particularly coastal lagoons.

Increasing protection of coastal ecosystems is recognized as a key strategy for the UAE that not only supports biodiversity, but also safeguard the nation’s largest blue carbon sinks that, if lost or degraded, can in turn release additional Green House Gas Emissions (GHGs) (IPCC 2019; Hilmi et al. 2021). The UAE National Determined Contribution (NDC, MOCCAE 2020) under the United National Framework Convention on Climate Change makes explicit reference to the initiatives that aim to conserve or restore blue carbon habitats as an adaptation measure with mitigation co-benefit.

Moving forward, greater collaboration between scientific research and policy making is critical to support compiling comprehensive blue carbon ecosystem inventories. It is highly important to measure the carbon storage and long-term emissions removal by coastal ecosystems, including coastal lagoons that typically are higher due to the dynamic environmental conditions, habitat maturity and biodiversity richness present in these areas. Such comprehensive inventories can form the basis of robust design, implementation, and reporting of blue carbon projects in the future. Science-based efforts to protect and restore blue carbon ecosystems are recognized as credible ‘Nature-based solutions’ supporting national climate plans to achieve Net-Zero by 2050 with measurable positive long-term climate mitigation and biodiversity outcomes (SBTi 2021; IUCN 2020).

The UAE’s coastal lagoons are at the heart of the economic activity of each emirate, with multiple stakeholders, such as tourism, real estate, ports and shipping, fishing, and recreation, benefiting from the ecosystem services of these coastal ecosystems, while often engaging in activities that sometimes have a negative environmental impact. These complex interconnections of natural and socio-economic systems can offer an opportunity to integrate protected areas into broader economic and social development plans and strategies for the UAE. Moreover, the rise of ecosystem valuation and natural capital studies have demonstrated a clear link between oceans and economic development (Hoegh-Guldberg 2015), therefore natural capital accounting can further support integrated management decisions in the future.

Progress is being made in the implementation of commercial and government sector guidance for social and environment safeguarding and for the realization of environmental net gain (Hooper et al. 2021). An integrated approach to coastal management can support effective biodiversity conservation in areas that fall outside of formally recognized protected areas (e.g., private land). The Kunming-Montreal GBF include specific targets of ‘Other Effective Conservation Measures’ (OECMs) recognizing that governance and management mechanisms other than protected areas can positively contribute to ecosystem and biodiversity conservation (IUCN-WCPA Task Force on OECMs 2019).

Designating protected areas within coastal lagoon seascapes and OECMs would ultimately need to be integrated into broader decision-making and land-sea use planning guided by national or sub-national Marine Spatial Planning (MSP) and/or Integrated Coastal Zone Management (ICZM). MSP and ICZM are broadly recognized by government, private sector and the scientific community as credible planning tools that can enable dialogue and engagement across multiple sectors to help identify optimum scenarios for activities (Katsanevakis et al. 2011; Santos 2019). Where ecosystem-based approaches are central, effective spatial planning can safeguard biodiversity and ecosystem resilience (WWF 2017). Key learnings from the increasing empirical knowledge on MSP and integrated ocean management implementation can offer valuable insights for the UAE decision makers. MSP and coastal management can benefit from natural capital studies and environmental impact assessments that are becoming increasingly important not only for development agencies, but also for financing institutions that are becoming more aware of their dependence on natural capital and the risks associated with biodiversity loss (TNFD 2022; DNB 2020).

Coastal wetlands and lagoons play a key role in global biodiversity persistence, so their effective management can elevate the national and international status of a designation. More than half of the currently listed Important Bird Areas (IBAs) in the UAE are coastal/marine (BirdLife International 2022) and at least three coastal lagoons have received recognition as Ramsar sites under the Ramsar Convention on Wetlands (Ramsar 2022). Three of the four protected areas in the UAE recognized by the prestigious IUCN Green List are coastal wetlands (https://iucngreenlist.org/explore/green-list-sites). Further expanding IBAs, Ramsar Sites, UNESCO World Heritage sites of cultural and natural importance in the UAE can offer a wide range of opportunities for scientific research, guidance on sustainable management of the coastal zone including MPAs, MSP, OECMs, as well as raising awareness among the public.

Given the proximity of coastal lagoons to urban environments, an integrated approach to managing these areas should also include citizen science and community programs that gather local knowledge, enable field activities contributing to science and conservation efforts, while creating environmentally-conscious behavior. Protected areas in coastal lagoons can also provide a platform for citizens to learn and enhance their physical and mental wellbeing as they interact with nature (Brymer et al. 2019). Ultimately, engagement of local communities and the public as well as citizen science initiatives are fundamental elements that can help advance the ‘science we need for the ocean we want’ as stated in the Implementation Plan for the United Nations Decade of Ocean Science for Sustainable Development (United Nations 2021).