The Sahara (2 page)

Sometimes it is easier, and more comfortable, to explore the Sahara from afar. The first satellite pictures taken of the desert, by NASA in 1981, provided clear evidence of something that anyone who lives or has travelled in the Sahara already knew. The desert was not always as dry as it is today. NASA’s photographs showed large and numerous dry riverbeds and wadis that provided clear evidence of a once extensive system of surface water.

Fresh, cold-water oasis

Even nowadays many of the wadis continue to function as they are meant to, periodically filling with water funnelled along the channels after the infrequent rainfall that comes to parts of the desert, albeit often less than annually. Finding the path of least resistance, the rushing water cuts its way through the softest beds of normally parched rock.

Today, the only permanent rivers in the greater Saharan region are on its edges, with the Nile and the Niger marking portions of the desert’s border along some of their course. Neither of these great rivers draws water from the desert itself but both rather rely on rainfall from wet highland areas in lands far beyond the Sahara’s borders. As the alleged traveller and writer Sir John Mandeville writes in his curious mid-fourteenth-century Anglo-Norman French travelogue, “Egypt is a long country, but it is straight (i.e. strait), that is to say narrow, for they may not enlarge it toward the desert for default of water.” Whether or not (although probably not) Sir John ever existed, let alone travelled to the ends of the earth as he claimed, the compiler of his Travels was more or less correct in this description of Egypt as a land hemmed in by the Sahara.

A far more reliable source of water are the oases, which appear in depressions where water is able to break through-for instance where there exists some break or fissure in the earth’s surface that allows the water to intrude on the land. While both the quantity and quality of the water found in the oases vary greatly, the fact that many of the larger oases have been continually inhabited for millennia gives a good indication of just how immense are the underground aquifers that supply them. The water in some of the aquifers below the Sahara was left behind at the end of the Pleistocene epoch, which lasted from approximately 1.8 million to 12,000 BCE, rightly earning this priceless prehistoric resource the name fossil water. Yet although the centuries-old presence of certain oases demonstrates the enormous capacity of these aquifers, it by no means guarantees that some of them will not lose their water at some point. Indeed, there are many examples of oases becoming extinct, and when the water supply disappears so too must the residents of those oases. Quite simply, without these oases, human habitation in the Sahara would be impossible.

Often thought of as underground lakes, the aquifers that lie beneath the Sahara instead of being recognizable, uniform bodies of water can more accurately be thought of as subterranean regions of saturated stone. It is the exertion of pressure on these wet underground rocks that feeds water up to the surface, like squeezing a sponge, in an unbroken flow. The Sahara is blessed with a number of such aquifers, of which two giant examples are especially noteworthy. The first is the Bas Saharan Basin, an artesian aquifer system that ranges not only under the majority of the Algerian and Tunisian Sahara but also stretches as far as Morocco and Libya, encompassing the entire Grand Erg Oriental region. The second great aquifer is the Nubian Sandstone System, which is located in the Sahara’s eastern and north-eastern quarters and is reckoned to cover in excess of770,000 square miles in the area of north-western Sudan, north-eastern Chad, south-western Libya and most of Egypt. Best estimates suggest that the Nubian Sandstone System contains somewhere in the region of36,000 cubic miles of groundwater. This single gigantic water system is responsible for supplying the majority of the water needs for all of the countries it lies beneath, with the exception of Egypt, which, as it has done since antiquity, relies on the Nile for most of its water needs.

At the other end of the spectrum, the Sahara contains some of the world’s least-visited massifs and mountain ranges, which are among the most isolated places on earth. One reason for the lack of visitors is that these high places tend to have sprung up in the Sahara’s more central, and subsequently less accessible, districts. This is a pity for anyone who enjoys wildernesses because these peaks are among the most rugged and remote locations the world can offer. In northern Nigeria, the Air Mountains reach higher than 6,000 feet, and the Ahaggar Mountains in Algeria rise above 9,000 feet. To reach the Sahara’s highest peaks, however, one has to travel to the Tibesti Mountains in the emptiest corner of northern Chad. Here, among the lunar peaks, is the Sahara’s highest point, Emi Koussi, a forty mile-wide volcanic cone that reaches a height of 11,302 feet, rising a mile and a half above the otherwise flat sandstone plateau that it dominates.

The Ahaggar Mountains from Assekrem

By far the largest proportion of the Sahara’s makeup is dun-coloured rock and stone in various forms, thousands of miles of gravel-strewn plains that can initially seem devoid of life or interest, especially for those who travel over these landscapes at speed. As Sven Lindquist once wrote: “In Sweden, when trying to imagine the desert, I thought of sandy beaches which never reach the water. But it is fairly rare to see beaches in the desert, which is more like an endless schoolyard.” These stony regions make up approximately seventy per cent of the Sahara, and consist of everything from plains of coarse gravel to plateaus of stripped rock and wadis.

Water’s presence does not necessarily mean that life there is sustainable. In the northernmost part of the Sahara, southern Tunisia is home to the Chott el-Djerid, the desert’s largest saltpan or, for the sake of technical accuracy, endorheic basin. The Chott el-Djerid is a highly saline marsh lake that covers more than 2,500 square miles, and which glistens a brilliant, crystalline white. A startling sight, saltpans are found in different parts of the world, but especially in hot deserts. Lacking an outflow, either on the surface or underground through permeable rock, any rain that falls into these basins is permanently trapped there, apart from that which escapes through evaporation thus forming the Fata Morgana or superior mirages of mountain ranges and fairy castles as seemingly real as the rocks beneath one’s feet. In high summer, it is also possible to traverse the salt lake on foot or, exercising due caution, in lighter vehicles, thanks to the presence of a semi-hard crust that forms during the period of blistering weather.

The sub-sea level conditions of the Chott el-Djerid are broadly the same in Egypt’s Qattara Depression, which marks the Sahara’s lowest point in places more than 400 feet below sea level; the depression is an area of 7,000 square miles, mainly saltpans and one-time marshes. Like the Chott el-Djerid, the Qattara Depression’s surface is saline and unstable, although there are guides willing to lead interested parties along one or more of the basin’s more stable paths. Of the few who do venture into these places, farmers are not among them, the salinity of the soil in both the Chott el Djerid and the Qattara Depression rendering agriculture impossible. Not even the highly salt tolerant palm tree can cope with the high saline content in the regions’ soil.

While in too high a concentration salt kills soil and prevents agriculture, it is vital and is the most precious of all the Sahara’s minerals. Rightly praised as a jewel among the desert produce, evidence of its importance can be found in the earliest human records found in the Sahara. To this day, great lengths are gone to in order to extract, process and sell this life-giving commodity, and wealthy empires have flourished in the Sahara just because of the presence of salt and its distant, hungry markets.

Among the most notable of the cities founded on salt are Taoudenni in Mali and Bilma in Niger, both of which have been centres of the salt trade for centuries. Whether through mining or harvesting from saltpans, the cargo was transported to the furthest ends of the Sahara and beyond. At the height of these empires it was not unusual for the annual camel caravans to number in the tens of thousands. Early accounts of such camel trains come from the great Arab travellers and geographers al-Idrisi and Ibn Battuta. Today, camel salt caravans have virtually disappeared, and the most sought after minerals lie somewhat further down in the form of oil and gas.

It is a great irony of modern Saharan travel, that while petrol-powered vehicles provide access to more of the desert to more people than before, they have also largely eliminated the need for camel transport, thus removing the romantic sight of a camel caravan that many travellers still dream of seeing. The greatest of late twentieth-century Saharan explorers are also not so far removed from their centuries-long Arab predecessors. Just as it was once geographers who recorded what they saw of the Sahara, today the majority of exploration is conducted by geologists, commissioned by patrons in the boardrooms of energy companies, sending them out to discover energy beneath the desert floor.

Flora and Fauna

If petroleum engineers are not usually thought of as overly interested in flora and fauna, perhaps they should be. After all, the precious oil and gas found in such quantities below the surface of the Sahara was once living itself Every species of plant and animal that now dwells in the desert has somehow evolved in order to survive in one of the world’s most demanding and unforgiving natural habitats. The camel - of whom more later - is only the most obvious example of an animal whose adaptations allow it to thrive where, for instance, the horse cannot.

Nor is the Sahara as devoid of life as the casual observer might imagine. Hundreds of species of insects live happily within its borders. Each species of ant, fly, moth, spider, centipede, locust and beetle manages to eke out an existence because all have adapted to the particular conditions of desert life. Water is obviously the key to all life, but in hot deserts and away from the oases the rarity, scarcity and unpredictability of rainfall have forced both plants and animals to evolve. In the case of certain species of frog and toad, their spawn can wait years for life-giving rainfall that will cause the swift reanimation of dormant life, with tadpoles sprouting and maturing in double-quick time.

Similarly, certain plant species have developed to allow the seeds to survive for years, and in some cases for decades, until a single shower will see them spring to life: seeds turn into seedlings and then rapidly become fully mature, flowering plants that disperse seeds of their own, which in turn lie waiting for the arrival of rain. A number of plant species support delightful names, including grasses such as the scrubby Cram-cram, which grows in low clumps often near the hardy acacia tree, and the Had, both of which thrive along the Sahara’s southern border. More impressive are the Sodom Apple or Calotrope, native to central Saharan regions, a large, woody bush with thick, fleshy leaves and pink flowers, and the pleasant-sounding and succulent Desert Melon, but be warned: the latter is a strong emetic, as any who have been tempted to feast on its ground-hugging fruit will attest.

Of the trees, the date palm is best suited to the desert. Able to survive with limited water and high levels of salinity, it is hardly surprising that the date is so highly praised in the folklore of the region and the Middle East as a whole. Acacia trees found in the desert, primarily but by no means exclusively in more mountainous areas, tend to be survivors of a past time instead of new plants, veterans of the Sahara rather than cadets.

Flora and fauna are both integral to the delicate ecosystem that exists in the Sahara, with the trees and smaller plants providing shelter and sustenance to any number of the animal species and with animals fulfilling their share of the bargain by assisting in the dispersal of seeds. For seed dispersal over the greatest distances, plants can do no better than to be eaten by a bird. Most bird species found in the Sahara are visitors. Crossing from West and Central Africa to take advantage of cooler European summers, they migrate south back across the desert to avoid the harsh northern winter. Although drawn by nature to this annual migration, the journey is long and extremely hard and many thousands of small birds do not survive. The corpses of doves, flycatchers, pigeons, pipits, swallows and thrushes will most often be found in early summer, killed by the heat and failure to find water while en route to Europe.