Guarding the flanks of Arabia are two main mountain ranges, both reaching higher than 3,000 meters in places (9,800 feet). One stretches south from Taif in Saudi Arabia to Yemen, the other curves from the Musandam peninsula of Oman, through the United Arab Emirates to southern Oman.
Both ranges are imposingly steep - indicating their relative youth in geological terms (10-30 million years or so) -and are the end product of collisions between land masses floating on molten lava. These collisions could be described as the final adjustments in the continental drift which started to break up the super-continent called "Panagaea" some 200 million years ago; at that time Panagaea included all the land masses we know as continents today, and the Arabian peninsula was still attached to Africa.
Mountains they most certainly are - and very impressive ones at that. But are they really "alps"? In a strict sense - mountains with permanent snow - no. While it does snow from time to time, the snow melts immediately. But in the general sense - high rugged mountains - they certainly are "alps" - at least if you consider the flora - and fauna.
Among the flora and fauna of Arabia are desert-adapted species which botanists classify as Saharo-Sindian, or Saharo-Arabian, and which zoologists classify as eremic. Mostly of African origin, these species have adapted to a climate which is essentially hostile to flora and fauna, in that they are at the mercy of highly irregular rainfall. As a result, many of these plants are now so specialized that they cannot live outside of the true desert regions in southern Arabia: from Jiddah to Aden and from Aden to northern Oman.
Most of these species, which originated in the dry tropics of Africa, do not exist in Europe at all. But in the high mountains of Arabia - 2,000 to 2,500 meters (6,560 to 8,200 feet) - a very different group of plants and animals occurs, whose origins lie in the temperate zone of Europe and Asia, the so-called Palaearctic region. Here, in splendid isolation, they continue to exist, though often separated from their usual home by thousands of kilometers.
All told, some 3,000 plants are found in Arabia, of which perhaps a quarter have their origin in the temperate zone. Nearly half of these are weeds whose status is doubtful; they may have been introduced by man. One example is the common European Dandelion (Taraxacum officinale) which has been found in only one locality in Arabia: the lawn of the British embassy in Sanaa. But that still leaves a hard core of some 300 plants which came originally from temperate zones and which are identical to those of Europe and Asia; other species have developed into distinctly Arabian species, such as the Arabian Thyme (Thymus lacvigatus), undoubtedly a distinct species but also representative of a large group otherwise found only in Europe and Asia.
Why are these temperate plants found deep within the desert and the tropical zone?
There are two main possibilities. First, they might have invaded these regions during a cool period of the ice ages, some 250,000 years ago, and might then have been trapped by a rise in temperature. Or they might be the survivors of an ancient stock dating back millions of years to a time when the world's climate was very different from that of today.
In the Yemen/Asir mountains, for example, many plants show signs of being immigrants that have maintained direct contact with the main range of the species until quite recently. Examples include the Giant Fennel (Ferula communis) and the lovely White Iris (Iris albicaus), which differ in no way from the Mediterranean examples. But nearby there are also species which can hardly be recent immigrants. A typical example is the Ethiopian Rose (Rosa abyssinica). A plant obviously derived from the temperate roses, the Ethiopian Rose - common in both Ethiopia and southwestern Arabia - probably developed into a distinct species before Arabia broke away from Africa some nine million years ago.
In Oman, the temperate flora show every sign of having been linked at some point with those of the Zagros mountains in Iran; at levels above 2,000 meters (6,560 feet), the flora are largely composed of temperate plants such as the large Star Thistle (Centaurea S.P.). Indeed, the first botanist to climb in the Musandam mountains region was overheard muttering, in effect, "I don't believe this isn't Iran."
There is, in fact, evidence that there was a land connection between the Zagros and Oman near Bandar Abbas as recen tly as 90,000 years ago, when climatic conditions would have permitted the interchange of such plants. And there may have been older affinities as well. Oman, for example, has a quite distinct Oleander (Nerium mascatense), allied to, but not identical with, the Mediterranean Oleander.
On the other hand, there are enigmas as well. The Carob (Cerahviia siliqua) is recognized by botanists as an extremely ancient plant from the Mediterranean region; it is mentioned in the Bible on several occasions. Its long flat pods are eaten in times of famine, and the weight of the seeds is the origin of the term "carat," now used as a weight measure of precious stones. It was long thought to be the only species in the genus Ceratonia, but in 1975 another species was discovered in Oman by the first Oman Flora and Fauna Survey. This connection between Oman and the Mediterranean must be very old indeed, dating back into the mists of pre-history. It may even be that the Mediterranean Carob descended from an ancient Arab stock. Another example is the Pomegranate (Punkagmnatum), widely cultivated in the Middle East and Arabia. There are only two species, one of which is endemic to Socotra Island. Was the Pomegranate also Arabian in origin?
In southwestern Arabia, the drier mountains of the Asir and Yemen have the highest proportion of temperate plants. On the barren summit of the Jabal al-Nabi Shu'aib near Sanaa, at 3,600 meters (11,800 feet), the highest in all Arabia, some 37 plants have been recorded including the Alpine Cress (Arabis alpina); the most genuinely alpine of Arabian plants, it is also found in the tundras of the USSR and the high mountains of Europe.
Also present are the Arabian Thyme (Thymus laevigatus), whose aromatic leaves make an excellent herb for cooking, and Forsskaal's Pink (Dianthus uniflorus), endemic to southwestern Arabia and closely related to the Alpine pinks of Europe. First found by Swedish botanist Petrus Forsskaal, a member of the Danish-sponsored scientific expedition to Yemen in 1761-62, Forsskaal's Pink does not have the delightful scent of many garden varieties. Another temperate species on Jabal al-Nabi Shu'aib is Botta's Chicory (Cichoricum bottae), which can be used as a coffee substitute. It was first discovered near Taif in Saudi Arabia by the Paul-Emile Botta, the rich 19th-century amateur scientist who unearthed the palace of the Assyrian king, Sargon II.
In the lush and well-watered southern provinces of Yemen, the situation changes as temperate plants become less dominant than they are farther north. Looking at the green summit of Jabal Subr above Taiz, this seems paradoxical, but there is a good reason: ample rainfall allows the survival of plants of African origin which cannot cope with the arid mountains north of the Jabal Sumara.
Temperate species are represented, however. One example is Botta's mullein (Verbasaun bottae), found by Botta almost certainly on the Jabal Subr. There are more than 100 species of mullein in Europe, Turkey and the Middle East, a few in southwestern Arabia, one in Oman and one - only - in the mountains of East Africa.
Among the most spectacular of the temperate plants in Arabia is the Arabian Primrose (Primula vertisolata), another of the plants found only in southwestern Arabia and Ethiopia. It is a moisture-loving plant, often clinging to cliff-sides from which fresh water oozes forth. Another is the Hairy Vetch (Vicia vilosa), a Mediterranean plant also present in the Asir and Yemen.
Writing about Jabal Subr, Carsten Niebuhr, of the Danish expedition to Arabia, said that the "exuberant fertility of Mount Subr affords, according to the accounts of the Arabs, plants of every species that is to be found anywhere else in the world."
In the gardens and fields of the high Arabian mountains, another group of temperate plants predominates. Those are the weeds which have developed in close association with the agricultural activities of man, and which are now almost exclusively found in artificial habitats. Whether they were present in ancient times is a moot point; man has spread weeds together with his crops since time immemorial. What is certain is that they are now firmly entrenched, often reaching pest proportions. One, for example, is the Water Crowfoot (Ranunculus rionii), a relative of the buttercup; it can clog watering streams and ponds with its beautiful white flowers. Another is the Plantain (Plantago), species of which are among the most cosmopolitan of all weeds, some surviving at lower levels in the tropics than most other temperate plants.
The distribution patterns of temperate plants are closely mirrored in the fauna. About 10 percent of the butterflies in the high Arabian mountains, for example, are of undoubted temperate origin, and among non-migratory birds we find the European Jay (Pica pica asircusis) in splendid isolation in the juniper forests of the high Asir; it has developed into a separate subspecies differing from the closest populations of the European subspecies in Turkey, more than 1,500 kilometers farther north (932 miles).
Technically speaking then, the high Arabian mountains may not really be "alps." But their flora and fauna are heavily influenced by those temperate regions in Europe and Asia, and when the cool sub-alpine zones of the summits are viewed from the shimmering heat of Asir's Tihama or Oman's Batina coast can't a slight exaggeration be justified?
Torben B. Larsen and John Wood are specialists in the flora and fauna on the Arabian Peninsula.