Location and General Description
Situated at the north east tip of the Arabian Peninsula, this ecoregion lies predominantly in Oman with a portion extending into the United Arab Emirates (UAE). To the west lies the Persian Gulf and Qatar; to the north the Strait of Hormuz and Iran; to the east the Gulf of Oman and Arabian Sea, and to the southwest the Rub’al-Khali (Empty Quarter) desert of Arabia. A number of small islands in the Persian Gulf are UAE territories, the majority of which are close to the mainland but a few are further out. This ecoregion completely surrounds two others in Oman, one being the Al Hajar al Gharbi montane woodlands and the other, a portion of the Arabian desert and East Sahero Arabian xeric woodlands, otherwise known as the Wahiba sands.
In Oman the ecoregion splits into two strips. The first of these is the northern Oman coastal Batinah plain which extends southeast past Muscat to the country’s easternmost point at Ras al Hadd before following the coastline south to the extensive mud flats off the Bar al Hikman. Opposite this is Oman’s largest offshore island, Masirah Island. The Batinah plain runs 270 km in length between the foothills of Hajar mountain range and the sea and varies in width from 3 to 30 km. It is scoured along its length by wadis (watercourses) from the mountains. A characteristic feature of the sandy beaches of the Batinah are the inlets of water called khors, sometimes containing mangrove stands and offering important habitats to birds (Gallagher & Woodcock 1980).
The second strip, referred to as the northern fans and pediments, is comprised of the southern flanks and plains at the foot of the Hajar mountain range. This gently sloping pediment is covered in gravels formed by water erosion after the range’s uplift in the late Eocene and Oligocene. A complex system of wadis running southwest drain the mountain flanks bounded in the southeast by the Wahiba sands and on the southwest by the great sand deserts of the Rub’al-Khali.
Satchell (1978) describes the UAE as having two distinct regions: an eastern mountain region with a sub-montane zone of outwash plains characterised by Acacia tortilis, and a western desert region divided into a coastal belt and inland desert and scrub characterised by ghaf (Prosopis cineraria) trees. In the eastern region, the barren, jagged mountains form part of the Hajar range in neighbouring Oman; they rise rapidly to 1,300m and then descend to a narrow coastal lowland plain along the Gulf of Oman. The northern ridges of these mountains, known as the Ru’us al Jibal or Musandem, face the Strait of Hormuz and are in an enclave of Omani territory. The highest peak is 2,087m, and the slopes drop precipitously, creating a highly irregular coastline with spectacular fjord-like valleys.
Geologically the Hajar and Musandem Mountains are comprised of paleozoic, metamorphic and igneous rocks formed at the site of a mid-oceanic ridge in the Indian Ocean. During the Tertiary and following uplift, erosion carved out spectacular scenery of rugged mountains, incised by sharply convoluted wadis. Fulner (1996) describes the Hajar mountains as constituting the world’s finest and most extensive surface exposure of rocks of the oceanic crust, with the grey-brown ophiolites being of special interest. Fossils can be found ranging from nearly 300 million to 8 million years ago.
The climate of the UAE is characterised by high temperatures (up to 490C in July), high humidity and low rainfall, typical of this ecoregion. Generally, annual average rainfall in the mountain region (140-200 mm) and along the east coast (100-140 mm) is higher in comparison to the gravel plains (100-120 mm), with the west coast receiving the lowest average of less than 60mm (Boer 1997). Oman’s Batinah coast receives an annual average rainfall of nearly 100 mm, mostly in winter (Gallagher & Woodcock 1980). The area of northern fans and pediment, located farther from the sea, are less humid.
The UAE’s four major habitat types support a range of plants that, according to Western (1989) and following further surveys, may number between 450-500 indigenous and naturalized species. Many show interesting adaptations to high salt levels, high temperatures and low rainfall. Along the coast, mangrove is represented by a single species, Avicennia marina. Common indigenous tree species are Zizyphus spina-christi, Prosopis cineraria and Acacia tortilis. Common trees of the Musandem and Hajar mountains are Moringa peregrina, Ficus cordata salicifolia, F. johannis, Acacia tortilis and Prunus arabica, the latter still used by the mountain tribes to make the shaft of the distinctive ‘Shihuh’ axe. Oman’s Batinah coast is dotted with thorn trees, mainly Acacia tortilis with Prosopis cineraria, in more sandy areas. The areas behind beaches and creeks contain salt tolerant scrub.
Certain species of vegetation in the Musandem Mountains show a link with Iran, which is due north across the Persian Gulf, separated by only 50 km at its narrowest point. Mandaville (1985) describes how the occurrence of species such as Artemesia sieberi Besser, Ephedra pachyclada Boiss and Astragalus fasciculifolius suggest that the southern Iranian highlands are an important centre of origin for the mountain flora of Oman. The high-altitude genera of Monotheca, Olea and Juniperus in Oman’s Al Hajar al Gharbi are absent in the lower Musandem mountains, possibly due to long-term climatic factors.
This ecoregion is a bird watchers paradise, with over 400 bird species recorded. The Arabian Peninsula serves as a staging post between Africa and Asia for migratory species, and the many lagoons, mud flats, khors and mangrove stands found along the Persian Gulf and the Gulf of Oman provide ideal nesting and feeding sites. An inventory of Important Bird Areas (IBAs) in the Middle East (Evans 1994) showed this ecoregion to contain 14 out of 33 areas identified in Oman, and 11 out of 20 areas in the UAE. Khor Khalba on the UAE’s east coast, bordering Oman, contains an endemic subspecies of the white-collared kingfisher (Halcyon chloris ssp. kalbaensis). This subspecies is endangered, with only 44-55 pairs remaining at the site (Aspinall 1996). The UAE contains a significant population of the Socotra cormorant (Phalacrocorax nigrogularis), a species endemic to the Arabian Peninsula and listed as endangered on the IUCN Red List (IUCN 2001); the population numbers around 200,000 individuals, representing 15-33% of the estimated world population (Aspinall 1995).
The Arabian leopard (Panthera pardus ssp. nimr) still exists in the Musandem and Hajar mountains but in very low numbers, certainly no more than 20 and probably far less than this figure (Stuart & Stuart 1995). This leopard is listed as critically endangered in UAE’s National Red List of threatened animals (Hornby 1996) and on the IUCN Red List (IUCN 2001). The Arabian tahr (Hemitragus jayakari), a type of wild goat, was photographed in the UAE Hajar mountains in 1995, constituting the first recent evidence that this ungulate survives in the UAE (Stuart & Stuart 1995). Periodic sightings still arise but numbers are precariously low and the animal is relentlessly hunted.
Fours species of turtles nest in the coastal areas, including the green turtle (Chelonia mydus), hawksbill turtle (Eretmochelys imbricata), olive ridley turtle (Lepydochelys olivacea) and the loggerhead turtle (Caretta caretta). The IUCN Red List categorizes Chelonia mydus as endangered and Eretmochelys imbricata as critically endangered (IUCN 2001). In Oman, the Ra’s al Hadd National Nature Reserve, 400 km southeast of Muscat, offers spectacular viewing. Here green turtles nest year-round and the site is considered to have the largest nesting population in the Indian Ocean, thought to exceed 20,000 (Baldwin 1996). Masirah Island contains the worlds largest nesting population of loggerhead turtles, with an estimated 23,000-30,000 females nesting every year (Baldwin & Al Kiyumi 1999).
The Indian bark gecko (Hemidactylus leschenaultii) was recently reported for the first time in Arabia and appears to be restricted to mature Acacia tortilis woodlands along the Batinah coast (Gardner 1992).
In the UAE, protected sites comprise both privately owned and government-designated reserves. Among the latter, Khor Dubai is protected by emiri decree and Khor Khalba was designated as a Nature Reserve by the Sharjah government. Planning is underway to develop a protected area network for the whole country, to be overseen by the Federal Environment Agency (Aspinall 1996). Oman is comparatively well advanced in the planning of its protected areas system. A system of Nature Reserves was proposed in 1986 (Clark 1986) and a coastal zone management plan was prepared during the 1986-1992 period. The Ministry of Regional Municipalities and Environment, and its Directorate of Nature Protectorates, is responsible for environmental protection. The Diymaaniyat Islands nature reserve, located off the Batinah coast, is classified as IUCN category IV – Habitat/Species management area, and the Ra’s al Hadd Turtle Reserve is also in IUCN category IV. There are also several other bird and nature sanctuaries.
Types and Severity of Threats
The whole of UAE’s sand dune system is subject to extensive grazing by camels and goats. Hunting and trapping of large mammal species has resulted in very low population levels of Panthera pardus ssp. nimr and Hemitragus jayakari. Oil spills are a threat to the entire coastline of this ecoregion, and 4-wheel drive vehicles cause damage to bird and turtle nesting sites. Off-road driving inland causes much damage to the vegetation, which is slow to recover due to the limited annual rainfall.
Justification of Ecoregion Delineation
This ecoregion boundary was formed using Zohary’s (1973) geobotanical map of the Middle East. It corresponds to Zohary’s classified regions of Acacietea tortilis ssp. sub-sudanica in the Palaearctic realm.
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Prepared by: Robert Llewellyn-Smith
Reviewed by: In process