Location and General Description
Situated in northern Oman, the Al Hajar al Gharbi montane ecoregion runs northwest to southeast in a 500 km arc paralleling Oman’s Batinah coast and extending roughly to Badiyah, not quite as far as Ras al Hadd on the easternmost point of Oman. The Arabic name means "the Western Hajar", and the mountain range has an eastern portion known as Al Hajar Ash Sharqi ("the Eastern Hajar"); the two portions are split by the Sumail gap. The highest part of the Al Hajar al Gharbi range is the limestone massif of Jebal Akdar (Green Mountain), lying between the western and eastern portions of the range. It has a breadth from north to south varying from 10 to 40 km and a maximum height of 2,980m in Jebel Sham. The mountains of Al Hajar Ash Sharqi have a maximum elevation of 2,152m.
Geologically, the Al Hajar Mountains are comprised predominantly of Cretaceous limestone and much of the geological time sequence is exposed. Textbook examples of folds, thrusts, and other structures, uplifted in Oligocene and Miocene times, are weathered to form a breathtaking landscape of dramatic peaks and precipices. Also included are metamorphic and igneous rocks that include the distinctive grey-brown ophiolites, formed in the earth’s lower crust and upper mantle and thrust to the surface to form jagged hills and mountains.
In the Jebel Akdar, December to March are the coolest months, often receiving violent thunderstorms, rain, hail and even snow. From April to September, temperatures increase, with occasional rain and thunderstorms brought on by the sporadic influence of the Indian Ocean monsoon winds. At about 2,000m on Jebal Akdar, extremes of temperature have been recorded (–3.50C in January to 34.50C in July) and an average annual rainfall for this altitude is 300-350 mm (Gallagher & Woodcock 1980). Temperatures in the foothills are higher and rainfall is unpredictable.
Except in gullies (wadis), the areas of ophiolite support little vegetation. In comparison, the richer soils of the limestone areas nurture more varied vegetation. Mandaville (1977) and Ghazanfar (1999) describe a marked altitudinal zonation. In the lower mountain areas, wadi species include Zizyphus spina-christi, Prosopis cineraria, Acacia tortilis and some fig species, especially Ficus salicifolia. Species richness is greatest from 1,000m-1,500m. On the steep slopes, Euphorbia larica is the characteristic species, associated with Acacia tortilis, A. gerardii and Periploca aphylla. Woodland vegetation occurs from 1,100-2,500m, where the characteristic species are Olea europaea, Monotheca buxifolia and Dodonaea viscosa. The uppermost zone, from 2,100m – 3,000m, occupies the summit area of the central range of the Al Hajar al Gharbi. Peculiar to this impressive landscape are large junipers (Juniperus excelsa ssp. polycarpos) that form open woodland, often co-dominant with Olea europaea.
Plant species diversity and endemism are both high compared to the surrounding foothills and the central plain. The northern mountains (including the Musandem Peninsula) contain 60% of Oman’s 1,204 species of vascular plants, of which 16 taxa are endemic to Oman (Ghazanfar 1998). The highland flora has affinities with the montane flora of southwestern Iran and neighbouring territories. Zohary (1973) describes a series of southern Iranian plant associations led by Euphorbia larica that appear to be near equivalents of the Euphorbia larica shrub communities found on the lower Jabal Akdar slopes. Madaville (1975) describes how the Reptonia-Olea zone of Jabal Akdar, between 1,350m and 2,300m, has a floristic equivalent in east Afghanistan. Ghazanfar (1998) suggests that the occurrence of Juniperus spp. and other plant associations in the Al Hajar range may be due to plant migrations from southeastern Iran across the Arabian Gulf. Evidence suggests that, in the past, sea levels fell to 120m below present levels, resulting in a land bridge between Asia and Arabia.
An African floral element is also present in Oman’s Al Hajar range, due probably to the linkage of the Arabian and African land masses during the Tertiary. An example is the tree Ceratonia oreothauma ssp. oreothauma, endemic to peak areas of the eastern Al Hajar Mountains, but also occurring in Somalia (Ghazanfar 1999).
The Arabian tahr (Hemitragus jayakari), a type of wild goat inhabiting precipitous mountain slopes and stark bare cliffs, occurs only in the mountains of northern Oman and the United Arab Emirates and is a regional endemic. Other members of the genus are the Himalayan tahr (H. jemlahicus) and the Nilgiri tahr (H. hylocrus) from the Nilgiri Hills and western ghats of southern India. The estimated total world population of H. jayakari in 1978 was less than 2,000 (Munton 1985) and the animal is classified as endangered on both the IUCN Red List (IUCN 2001) and Oman’s preliminary National Red List (Fisher 1999) of threatened animals. Small populations of mountain gazelle (Gazella gazella) exist, particularly in the Wadi Sareen Reserve.
The mountains contain three nationally endemic species of geckos: Asaccus montanus, A. platyrhynchus and Pristurus gallagheri. Five additional regionally endemic geckos and lizards are restricted to the mountains: Asaccus caudivolvulus, A. gallagheri, Pristurus celirrimus, Lacerta jayakari and L. cyanura (Gardner 1999).
The Oman Flora and Fauna Survey (1975) recorded 71 bird species for the Jebel Akdar area, including 28 residents and 41 migrants (Gallagher 1977), out of a total of 451 species recorded in Oman (Eriksen 1999). The mountains support a population of the lappet-faced vulture (Torgos tracheliotus), significant in the Middle East since the species is threatened and declining in the region; it is listed as vulnerable on the 2000 IUCN Red List (IUCN 2001). In addition, 5 species restricted wholly or largely to the Middle East are resident here (Evans 1994), including Alectoris melanocephala, Ammoperdix heyi, Otus brucei, Oenanthe monach and O. alboniger.
Of the carnivores, the Arabian leopard (Panthera pardus ssp. nimr) disappeared from the Omani Al Hajar Mountains in the 1970’s as a result of severe persecution by man (Spalton & Willis 1999). The Al Hajar Ash Sharqi are reported to have small numbers of Arabian wolf (Canis lupus), striped hyaena (Hyaena hyaena) and possibly Gordon’s wildcat (Felis silvestris) (Fisher1999).
The Ministry of Regional Municipalities and Environment (MRME) and its Directorate of Nature Protectorates is responsible for nature conservation in Oman. A detailed conservation assessment of the country carried out in 1986 resulted in a proposal for a system of Nature Conservation Areas (Clark 1986) and provides the basis for all terrestrial protected area work. The Office of the Adviser for Conservation of the Environment, Diwan of Royal Court, assists the Ministry and is responsible for managing the Wadi Sareen Reserve, created primarily for the protection of Hemitragus jayakari. Here, rangers patrol an area of c. 1,800 km2. MRME rangers also protected Hemitragus jayakari and Gazella gazella in the Jebel Qahwan-Jebal Sebtah area in the Al Hajar Ash Sharqi.
Types and Severity of Threats
Overbrowsing by camels, goats and feral donkeys threatens the vegetation resource. Although not serious, young branches and fresh leaves are cut for fodder. Increased housing development and road building pose a threat to vulnerable sites and species-rich habitats. The endemic Ceratonia oreothauma ssp. oreothauma in the Al Hajar Ash Sharqi is classified as ‘vulnerable’ in Oman’s National Red List, threatened by heavy browsing and lopping for fodder and showing little or no regeneration (Ghazanfar 1998). The juniper woodland from 2,100m to 3,000m shows poor regeneration, apart from a few locations, perhaps due to human disturbance, grazing pressure and climatic change (Gardner & Fisher 1994). Below 2,400m, the trees are either dead or in very poor condition and regeneration is minimal (Fisher and Gardner 1995).
Survival of the Hemitragus jayakari is threatened by competition with domestic goats and by development projects, particularly mining, that threaten vegetation and water sources (Insall 1999). Insall also reports that while illegal hunting has diminished with increased ranger protection, a more recent threat is one of poaching to satisfy demand outside Oman.
Local people in the northern mountains have their own traditional method of resource conservation through the establishment of hamiyaat, traditional livestock-free protected areas where fodder is cut by hand. Similar traditional protected areas in which livestock are excluded are found in Saudi Arabia and termed himas. However, abandonment of key hamiyaat has led to further grazing pressure and further loss of suitable habitat for Hemitragus jayakari (Insall 1999).
Justification of Ecoregion Delineation
This ecoregion is located in the Al Hajar range of northeast Oman. The boundaries are derived using Zohary’s (1973) geobotanical map of the Middle East. The region corresponds to Zohary’s savanna of Acacietea sudano-arabica vegetation (mainly Acacia-Commiphora scrub).
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Prepared by: Robert Llewellyn-Smith
Reviewed by: Fred Launay