Red Sea Nubo-Sindian tropical desert and semi-desert
Located chiefly on the Arabian Peninsula in the Middle East, the Red Sea Nubo-Sindian tropical desert and semi-desert ecoregion consists largely of level desert terrain, punctuated by scenic and topographically distinctive rocky landforms.
There is limited biodiversity in this extreme climate, which at times receives little or no rainfall for years at a time. There have been a total of 432 vertebrate species recorded in the ecoregion. Characteristic fauna includes the Arabian White Oryx, Sand Gazelle, Sand Dune Cat and Ruppell's Fox.
Location and general depiction
This ecoregion consists largely of vast generally level expanses of sand, gravel or lava plains, sometimes monotonous in character and incised periodically by gullies (wadis). In some areas the topographic relief is punctured by isolated granite and sandstone mountains, and there is a high mountain range in the southern Sinai Peninsula. In Jordan, the Wadi Rum forms a maze of spectacular sandstone cliff scenery with "great bastions of rock, skewered and scrolled and fissured and wrinkled by salt, sand and wind into shapes" that not even a delirious mind could invent.
In Oman, the ecoregion starts at the Huqf depression close to the Bar al Hikman on the east coast. Heading south, it then incorporates the central plains of the Jiddat al Harasis plateau, an area now home to re-introduced Arabian Oryx (Oryx leucoryx) and other wildlife of the Arabian Oryx Sanctuary.
Further south and west, the central plains give rise to the Dofar pediment. Here a complex system of wadis drain the inland face of the Dhofar mountain range and run north until deflected and overrun by the sand dunes of the Rub' al-Khali. Extending southwest into Yemen, the ecoregion intercepts the Mahara and northern Hadramaut Governates. The start of the Wadi Hadramaut, an area noted for its settled agriculture and ancient towns, is included. It then extends northwards into Saudi Arabia up as far as the Jordanian border, where the terrain is characterized by fairly monotonous gravel plains and sparse vegetation. However, these plains are often interrupted by large areas of black volcanic lava desert known as harrats, strewn with volcanic boulders that make these areas virtually inaccessible by vehicle. Rising above the plains are several mountain ranges, including the Jabal Aja' and Jebal Salma near Hail in the north, which are essentially rounded domes of weathered granite.
The coastal plains and rugged mountains of the southern Sinai add considerable interest to this ecoregion. The mountains of the St. Catherine area reach an elevation of 2624 metres (m), and their smooth granite slopes and near vertical faces contribute to the spectacular mountain scenery. Deep gorges or wadis are notable topographic elements, with some containing water throughout the year. The mountains are comprised of acid plutonic and volcanic rocks belonging to the Precambrian basement complex of the southern part of the Sinai Peninsula.
The climate is characterized by high summer temperatures and cold winters with low annual rainfall; periodically little or no precipitation occurs for several consecutive years. For example, Oman's central plain receives an annual average rainfall of less than 50 millimetres (mm), and in some years receives no rain. Rainfall for Mahazat as-Sayd near Taif in Saudi Arabia is variable and ranges from 50 to 100 mm, while mean monthly minimum and maximum temperatures vary from 20C to 210C and 290C to 400C, respectively. Over a 25-year period, the mountains of the Saint Catherine area in the southern Sinai showed a mean annual precipitation of 45 mm, although the highest peaks receive more precipitation (100 mm) as rain and snow. On Mount Sinai, mean monthly temperature ranges from -10C to 20C in winter to 170C to 190C in summer.
The vegetation in this ecoregion is sometimes referred to as a pseudo-savanna. The spaces between the scattered trees and larger shrubs are occupied by smaller shrubs and herbs; grass-cover may sometimes appear, but only after a plentiful rainfall. The wadis and gullies tend to support most of the vegetation, due to generally higher soil moisture levels in such ravines. Common plants include species of Acacia, notably A. tortilis, A. raddiana and A. gerrardii, as well as Christ's Thorn Jujube (Ziziyphus spina-christi), Desert Date (Balanites aegyptiacus), Toothbrush Tree (Salvadora persica), Moringa peregrina, Karira (Capparis decidua), Cordia gharaf, Giant Milkweed (Calotropis procera)and many other plant taxa. On Oman's central plains, common trees are Acacia tortilis and A. ehrenbergiana, with Prosopis cineraria in areas of deeper sand accumulation. The most widespread and abundant grasses are within the genus Stipograstis.
On Oman's central plains, the Arabian Oryx Sanctuary covers around 25,000 kilometres2 (km2). A World Heritage site, it supports a diverse wildlife community, made famous for the successful reintroduction of the Arabian Oryx (Oryx leucoryx). It contains the largest population in the Arabian Peninsula of Arabian Gazelle (Gazella gazella ssp. cora), estimated to number about 5000 individuals, with positive fluctuations after plentiful rain years. Other mammals include the Goitered Gazelle (Gazella subguttorosa), Dorcas Gazelle (Gazella dorcas), Sand Dune Cat (Felis margarita) and Ruppell's Fox (Vulpes rueppellii). It is one of the few sites on the Arabian Peninsula hosting a resident Houbara Bustard (Chlamydotis undulata) population. This part of the ecoregion is unusual, in that it receives supplemental moisture up to 120 km inland from the coastal zone, provided by heavy dews and fogs influenced by southwest monsoons. Even though species richness is low, eleven endemic plant species are found in the ecoregion.
The Mahazat as-Sayd Special Nature Reserve (2200 km2) is another key re-introduction site, containing re-introduced Oryx leucoryx and Arabian Sand Gazelle (Gazella subguttorosa ssp. marica). The IUCN Red List categorizes both species as endangered. The population of Arabian sand gazelle was estimated at approximately 300 in 1994. Also introduced to the site is the Somali Ostrich (Struthio molybdophanes) from the Sudan as a replacement for the indigenous Arabian Red-necked Ostrich (Struthio camelus ssp. syriacus) which became extinct in 1940. The vegetation in this reserve made a notable recovery after fencing to keep out livestock; the number of plant species increased from 112 to 142 between 1989 and 1994.
Boulos et al. describes the southern Sinai and northern Hijaz area as a center of plant diversity and endemism in the Saharo-Sindian Regional Zone. The 16,000 km2 area contains approximately 700 vascular plant species, of which about 35 taxa are endemic with one endemic genus. The flora includes Mediterranean, Irano-Turanian and Saharo-Sindian elements. The southern Sinai is estimated to contain 28 of the endemic species, most of which are found in the gorge habitats of the Saint Catherine mountains.
In northern Saudi Arabia near the Gulf of Aqaba, the Jebal al Lawz granitic mountains contain at least twenty peaks at over 2000 m. The highest peak is Jebel Fayhan at 2549 m, high enough to receive snow in winter. Vegetation zones are evident, with some stunted Juniperus spp. on the summits. The site is of great botanical interest as it contains wild date palm (Phoenix dactylifera), the only site in Arabia of Wild Almond (Prunus dulcis), and one of two sites in Arabia of Wild Tulip (Tulipa biflora). This is also the only site in Saudi Arabia containing numerous birds of the Chukar Partridge (Alectoris chukar).
Also of importance to wildlife is the Jebel Aja Mountain range and the northern Ha'il extension into the Nafud Desert in Saudi Arabia. The site lies at the center of the spring flyway for the threatened African wintering population of Gus virgo. In addition there is an impressive spring migration of swifts, larks and wheatears, together with a gamut of raptor species. Other characteristic avifauna are the Houbara Bustard (Chlamydotis undulata), Lichenstein's Sand Grouse (Pterocles lichtensteinii), and Chestnut-bellied Sand Grouse (Pterocles exustus).
Oman, is an endemic reptile to this ecoregion. Tilbury's Fringe-fingered Lizard (Acanthodactylus tilburyi), found in southern Jordan and the Ridyadh region of Saudi Arabia, is another reptile endemic to this ecoregion. The Critically Endangered Egyptian Tortoise (Testudo kleinmanni) is found within the ecoregion. Other reptiles found in this ecoregion include the Grey Monitor (Varanus griseus); Thomas' Mastigure (Uromastyx thomasi); and the Arabian Fringe-fingered Lizard (Acanthodactylus arabicus), native to south and central Yemen, known from wadis below Mount Manif, Aden, Hadramaur, Lahej, Jimil Valley, Abian Hills, Bir Fukom, Shugra, Bal-Haf-Azzan and Wadi Irma. Snakes found in the ecoregion include the Arabian Sand Boa (Eryx jayakari); Black Desert Cobra (Mesalina ayunensis); Field's Horned Viper (Pseudocerastes fieldi); Mediterranean Spur-thighed Tortoise (Testudo graeca VU).Arnold's Sand Lizard (Mesalina ayunensis), found in southwest
The main responsibility for wildlife conservation and environmental protection in Yemen lies with its Environment Protection Council. Up to 1994, no areas had legal protection and little information exists on the current situation, although Miller indicates that UNEP and IUCN have recommended a network of reserves.
Nature conservation and protected area management in Saudi Arabia is the responsibility of the National Commission for Wildlife Conservation and Development (NCWCD) established in 1986. Its protected area plan builds on the existence of traditional resource conservation areas or himas, of which Draz estimated there to be 3,000. In Oman, the Ministry of Regional Municipalities and Environment, and its Directorate of Nature Protectorates, is the principal body responsible for environment protection and wildlife conservation. The Office of the Adviser for Conservation of the Environment, Diwan of Royal Court, shares this task and is responsible for managing the Arabian Oryx Sanctuary.
In the southern Sinai, the Egyptian Environmental Affairs Agency (EEAA), through its Nature Protectorates division, has established several protected areas. The Saint Catherine Protectorate incorporates a unique high altitude desert ecosystem and covers an area of 4,350 km2. The Abu Galum and Nabq sites on the east coast protect mountain and coastal biodiversity, while the Ras Muhammad National Park protects marine and terrestrial areas of the Ras Muhammad Peninsula.
The Jordanian Royal Society for the Conservation of Nature (RSCN) is in the process of creating the Wadi Rum Nature Reserve, planned to cover approximately 500 km2 (RSCN 1994). The Reserve will address problems of overgrazing and damage to archaeological sites as well as provide protection for wildlife, including the ibex (Capra ibex ssp. nubiana) and Gazella subguttorsa.
Ecological threat profile
Common threats to biodiversity are wildlife poaching, overgrazing by camels and goats, and damage to vegetation through off-road driving. The wildlife inhabiting Oman's central plains are formally protected in the Arabian Oryx Sanctuary. Despite the protection, however, poaching reduced the number of re-introduced Oryx leucoryx in the sanctuary from over 400 in 1996 to 136 by January 1999. Off-road driving by local bedu, visitors, and seismic operators exerts a damaging effect on vegetation, both in the sanctuary and the surrounding area, although no studies have yet been conducted to examine the damage. A further threat to the vegetation in the sanctuary and surrounding central plains is overgrazing by goats and camels. During the last 20 years, livestock herds have increased as the local nomadic pastoralists have purchased pick-up trucks that provide greater access to borehole water and the transport of supplemental feed.
Justification of ecoregion delineation
The area corresponds to Zohary's geobotanical zone of Acacietea tortilis sub-sudanicain the Afrotropical realm.
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- Miller, A. G. 1994. Highlands of South-Western Arabia: Saudi Arabia and Yemen. Pages 317-319 in S. D. Davis, V. H. Heywood and A. C. Hamilton, editors. Centres of Plant Diversity, Vol.1. WWF, IUCN, Gland, Switzerland. ISBN283170197X
- Royal Society for the Conservation of Nature. 1994. Wadi Rum proposed as a new nature reserve. Arabian Wildlife 1(1):34.
- Sibley, C.G. and B.L. Monroe, Jr. 1990. Distribution and Taxonomy of the Birds of the World. Hancock House Publishers. ISBN: 0300049692
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