Deserts in Saudi Arabia

30% of the land in Saudi Arabia is covered by sandy-deserts. Although the desert of Saudi Arabia is more or less continuous, extending from North to South, the Nafud in the north and the Rub-al-Khali in the south are the largest among all. Other sand bodies, such as the crescent-shaped Dahna situated in the Najd Area and the Al-Jafurah on the Eastern region are relatively smaller in size. Rub-al-Khali occupies an area of about 650,000 sq. km with sparse vegetation. Sand dunes in this desert often reach a height of about 250 m, especially on the eastern side of the country. Rainfall is almost nil in this desert. Yet sporadic rains measuring about 35 mm/year are reported in some years. Vegetation composed of diffuse shrubs. Annual plants are virtually nil in this desert. Rub-al-Khali or the ‘Empty Quarter’ is believed to be the largest continuous sand body in the world and supports the life of at least a few endemic plants such as Calligonum crinitum spp. arabicum, Tribulus macropterus var. arabicus (Tribulus arabicus), Cornulaca arabica, etc.

The Great Nafud is composed of transverse sand dunes that often reach up to a height of about 120 m. The sand of Nafud is reddish in colour due to iron oxide coating while the sands of other deserts are somewhat yellowish in colour. The sandy deserts of the central Saudi Arabia consist of an arch-shaped Dahna in the east and a number of smaller sand bodies such as  Nafud Al Mazhur, Nafud ath Thuwayrat, Nafud as Sirr, Nadud Qunayfidhah, Nadud ash Shuqayyiqah, Al Urayq, Irq Subay, etc. The sands in these bodies contains high sand ridges with flat interdune beds with shallow, stable sand.

Life in the desert, particularly plants, insects, lizards, rodents, snakes, birds, etc. are highly dependent and each one helps in the survival of the others. As the rains in the deserts are intermittent and erratic, every drop of water that fall on the sand is precious for the existence of plants and animals. Plants have several adaptations that help them to survive in the desert, such as ability to collect and store water, features that help reduce water loss, etc.

Saudi Arabia’s desert ecosystem possesses one of the harshest environments for living beings. However, both animal and plants adapted various forms to adjust their life in that inhospitable habitat. In many situations, such life in the desert is uncompetitive, as many plants particularly tropical and temperate plants do not exist in sandy or rocky deserts due to their inability to adapt hot desert climate. Majority of desert plants do not have broad leaves, rather represented by scaly or needle-like leaves as in the case of Tamarix, Haloxylon, Calligonum, etc. In order to prevent excessive transpiration rate, plants have thick cuticle or waxy coating over stem and leaf surfaces, or have sunken stomata or possess multilevel epidermal layers. Sand covered strong-roots that help to penetrate deep into the soil in search of water and also help the plant to hold firmly on the ground against sand-storms. As far as the animals are concerned, the source of water comes from the plants, while in the case of carnivorous creatures /animals the water need is satisfied by the fluids contained in the bodies of the animals that they live upon.

Many desert species, especially Vachellia spp. have very long tap root system, which often go deep into the soil in search of moisture. The same plant, if grows on wadi produces extensive feeder roots to tap the easily available subterranean water. Their main tap- root may not go deep in search of water. Uprooting of such plants along wadi bed is quite common in Saudi Arabia during flash floods. The above ground parts of many desert plants, particularly short lived perennials or plants having bulbs shed their shoot system during summer months and remain alive at subterranean level and grows again after the first showers during early winter.