Plant Diversity Hotspots in Saudi Arabia

The most important topographic and floristic diversity of Saudi Arabia can be seen in the mountainous North and South Hijaz regions, stretching parallel to the Red Sea coast. Various scientists and explorers have carried out several studies during the past few decades to explore the vegetation of these regions. The mountains of south western region are more or less continuous with peaks reach elevations of over 2000 m in the vicinity of Taif and over 3000 m southwards, towards Abha. The stony mountains in the north-western region, on the other hand, are generally discontinuous with peaks reach between 1500-2800 m.  Isolated mountains in north central Saudi Arabia and an arch like Jabal Tuwaiq, extending the entire central region are less elevated, ranging between 1000-1500 m. Unlike the vegetation of northern and southern Hijaz Mountains, the vegetation in other parts of the country including that of sand seas and range lands in the central and northern region is less important in terms species diversity.

The vegetation of Raida escarpments (1500-2800 m), previously an inaccessible one due to the region’s steep slopes, is now facing degradation because of increased pastoral activity. Though this escarpment is protected and containing a large number of trees including Juniper forests in pristine conditions, the populations of a moderate number of species, including some of the rare species such as Huernia saudi-arabica, Ceropegia spp., Scadoxus multiflorus, Klenia odora, Adenia venenata etc., are increasingly marginalized during the past few years. All these threatened populations do not have more than 50 plants/10 sq. km.                       

Mountains in the Fayfa region, close to Yemen borders, and other isolated mountains like Jabal Abu-Hassan also harbor a diverse flora, which is more or less similar to that of East African, one. A considerable number of endemics have also been reported from these regions. Fayfa Mountains (2000 m) which receive a constant moisture-laden breeze on the west facing slopes support the life of many endangered species including few remaining stands of Dracaena ombet, Dorsetnia foetida, Ceropegia spp., Rhytidocaulon spp., etc. Though the mountains in the Saudi-Yemen border do not have any remarkable variation in terms of precipitation and temperature, the density and variation in the vegetation of Yemen are apparently higher than that of the Fayfa Mountains. This is perhaps due to the increased urbanization practices or the effect of centuries-old terraced cultivation on virgin lands. A considerable number of species recorded from the northern mountains of Yemen have so far not been collected from Fayfa Region. The ways to trace those species, which were disappeared from these mountains (local extinction), are virtually, nil, as all previous literature covering this part of the region did not mention any exact collection detail or all collections are from within the borders of Yemen only.