During the second half of the 19th century, archaeologists unearthed ruins in the desert, sometimes large ones, evidence of great cities that appeared before their astonished eyes. It was obvious that certain ancient civilisations had existed in regions that today have an arid, sub-arid or desert environment. It was reasonable to deduce that these now arid regions could not have supported the needs of these ancient societies, and that the climate had changed in historical times. This climate, which has changed so fundamentally over the long history of our planet, was the result of major ice ages during the Quaternary. During their retreat, about 8000 years ago, the ice cap was still at the mouth of the Thames. The Sahara had a temperate climate at that time and the people who lived there created a civilisation, and from that time onwards the retreat of the ice to the north was slow with a series of oscillating movements.
At the end of the 19th century, when these ideas were beginning to take hold with precision in the minds of scientists, Pierre Kropotkin, a friend of the French geographer Elysée Reclus, discovered in the steppes of Turkestan forests of dried-out, sometimes solidified, trees stretching for hundreds of kilometres. Famous for his geography and his anarchist convictions, this Russian not only understood that this was a sudden change, he was the first to deduce historical consequences from this phenomenon. The degradation of the land had caused the nomads to migrate westwards to better pastures. This explains the movement of barbarian hordes towards these regions, in a word, the displacement of masses of people towards the green and fertile valleys of our continent.
Silicified tree trunks: Huntington’s findings
To confirm these observations, the Carnegie Institute of Washington sponsored a major exploration in Turkestan in 1903, led by the American geographer Raphael Pumpelly. These explorers recognised the importance of the area of dry trees, mostly poplars, and were accompanied by the soon-to-be famous American scientist Ellsworth Huntington. He immediately became aware of the importance of the climate changes that had taken place in history, a theme to which he dedicated the first part of his life. He quickly confirmed Kropotkin’s hypotheses and began major studies using various methods of investigation. This research lasted from his first notes on Turkestan in 1905, until the publication in 1924 of the third edition of his work: Civilisation and Climate, the synthesis of his efforts. Huntington and other specialists convinced by his teachings made numerous investigations to verify the variations of water levels in certain Asian lakes, in relation to the situation of certain known ruins. These investigations on the water levels, which were used for the construction of the reference monuments, showed great oscillations in the level of the waters, which decreased or increased according to the periods and their rainfall. The Caspian Sea, a closed sea that bears witness to a vanished Tertiary ocean, was particularly suitable for these investigations, since important civilisations had developed on its shores over the course of time. They also studied facies changes, both botanical and zoological, in areas that are now deserted. Albrecht Penck (1858-1945), one of the founders of glacial geomorphology, observed the movements of vegetation and dunes in the southern Sahara, and confirmed Huntington’s work. The oscillations of Mother Nature of a glacial or torrid climatology were manifested according to a succession of geographical frames, following each other in a determined order, characterised by precise geobotanical observations. Subpolar vegetation could not suddenly give way to subarid species. A series of interludes must have existed for each of its extremes, which was of paramount importance for reconstructing the past landscape.
Other research took very curious methods, for example a study in the Syrian desert succeeded with the help of historical testimonies in establishing statistics with which to record the number of caravans that crossed this region on their way from Damascus to Chaldea. In this way, it was possible to determine the dates of the changes of trajectory, when these routes had become dangerous due to the lack of water and were abandoned. These facts demonstrated oscillations in rainfall and drought activity in these regions, which were once rich and fertile as evidenced by ancient texts and archaeology.
With these methods, which are half geographical and half historical, one could only make general statements: the climate had changed since antiquity. It was certain that a process of drought had occurred since the 2nd century and had subsequently become intense. It was impossible to determine a precise climatic situation with reference to a region in the past. The only thing that remained within the capacity of the researchers was to induce relationships between the climate crisis and past events. This was not the case with the methods used by Huntington, which had the rigour of mathematical calculations that could be applied to any circumstances of space and time. He soon realised that the double radial impressions that appeared in the cross-sections of large trees that had been cut down, and if averaged over a large number of specimens, determined not only the age but also the dryness or humidity characteristics. There is a gigantic tree in California, the Washington Sequoia, which is up to 3,500 years old, and for specialists it is a real weather archive. Huntington studied 450 of them in detail and with his calculations he established exact and precise graphs. Parallel research on Owens Salt Lake, fed by a river of the same name whose waters lead to Los Angeles, near the Huntington redwoods, confirmed Huntington’s data through numerous analyses of the salts present in the lake and the river.
These data, which are very important for historians because the redwoods and the lake are at the same latitude as the Mediterranean, were confirmed by the work of the Swedish geologist Gerard de Geers, who studied the deposits left by the retreating glaciers as a result of higher temperatures. In 1940 he established a chronology of the climatic situation over the last few thousand years, and these results, obtained using completely different methods to those used by Huntington, which nevertheless corroborate, remove any hesitation. Nowadays, we can study the evolution of the climate in historical times and fix the major atmospheric crises with precise dates.
Climate has shaped our history
Historians cannot ignore these lessons: important civilisations, such as the one that developed in Mesopotamia, had disappeared corroded by drought. Wind erosion had buried Sumer, Nineveh, the immense Babylon under the sands. On the contrary, other civilizations disappeared because of a reverse phenomenon: the Mayans and the Khmers who built magnificent temples at Angkor, and other lesser known ones were suffocated under the rainforest, which suddenly appeared dismantling their civil and religious constructions, whose ruins are behind thick foliage. Thus, the changes in climate over time, transforming the environment of these ancient societies, was one of the keys to understanding the evolution of universal history.
However, the historian faced a great difficulty: he had to date every change in the landscape, every natural setting, if he did not want to consciously fall into gaudy anachronisms. During the Middle Ages, the Iberian Peninsula had a different climate from that of modern times, and this lack of knowledge was due, among other things, to the mythical nature of Spanish history. Thus, in order to establish the particular case that interests us in this thesis, i.e. the past facts of the 18th century, it is necessary to reconstitute the natural framework of that time, which was the consequence of the general evolution of the climate in our hemisphere. Since this was correlated with the atmospheric situation of the Sahara, this problem was reduced by determining the last transformation of this desert, i.e. the date on which it changed from a steppe environment to an arid one. From what we know, it is reasonable to place this mutation during the High Middle Ages, and if this is correct, we must admit the existence of a connection between the mutation of the landscape and the economic and political crisis that had ravaged the Maghreb and most of the Iberian Peninsula at the same time. In other words, the Islamic revolution was reciprocally linked to this process of desertification of the Sahara.
Angkor site: Relativisation of Saharan desertification
Most geographers agree on the following principles: the current deserts are of recent formation. One could argue about the climatic mechanisms, but what is not in doubt is that the process of aridity increasing to a desert has not been simultaneous in all regions. There are ancient deserts and recent deserts. Because of the gigantic dimensions of the Sahara, about 5000 km long from the Red Sea to the Atlantic, and 2000 km wide from the Atlas to the Sudan, almost 10 million square kilometres, the process of aridity could not be the same in all places. The desert side of its western part is more recent than the eastern one.
How can we appreciate this difference? Émile Félix Gauthier, one of the first to have studied the Sahara, used a very appropriate term. He said that ancient deserts like Libya were in an “aseptic” state. By this he meant that the geophysical and climatic conditions in these regions were so severe that life was almost non-existent. The fauna and flora had disappeared and caravans did not cross them, with the ancient means no one dared to do so. On the contrary, the western desert, which was formed more recently, had important wells, and the remains of vegetation testified to a previous situation that was already over. There is still a specialised and widespread fauna, and in some places in winter there is enough pasture to feed a few herds of goats and camels, and nomads and caravans still pass through these places. The geophysical facies also confirm the existence of a divergence in the time when the soil deteriorated. In the Eastern Sahara, the river systems are filled in and blocked by wind erosion, and the sands hide the reliefs once sculpted by the waters, giving a landscape of grandiose, but lunar uniformity. In the western part of the Sahara, on the other hand, a fossil river system remains. The water no longer flows into these great Quaternary valleys, carved by rivers and streams that have now dried up, but they can be easily recognised. The closer one gets to the Atlantic, the more the wadis retain the same geophysical context as the European rivers. Thus, in the Rio de Oro, one can find the meanders of the Seguia el Hamra, whose rivers are devoid of vegetation, but whose bed still maintains its sinuous course of a living river. This thesis will only focus on the Central and Western Sahara areas to understand the role played by climate change with the events of the 8th century. But even in these two areas the processes were not the same, the one in the central region was much more pronounced. There is a tanezrouft or ‘thirsty desert’ there, which reaches 150-300 km in its north-south dimensions. This area is surrounded by highly altered xerophytic steppes in which the landscape changes to a sub-arid vegetation, and then becomes very arid as one moves towards the Mediterranean or Niger. A desertification process always occurs in several stages where the change of the landscape varies successively from steppe to sub-arid, from sub-arid to arid, and modifies the climate of the peripheral zones. This law of correlation makes it possible to reconstruct the succession of landscapes that existed in the past. It is sufficient to gather sufficient historical evidence to determine the existence of ancient natural settings, and if possible, to establish the chronology of its mutations. This task is made easier by the fact that it is a recent process, and geobotanical and biological evidence can still be recognised.
Conifer in the Tassili: North Africa’s vanishing forests
Snail farms, which are places where snails were prepared for export and consumption, are found by the thousands in southern Tunisia. The analysis of the ashes of the pyres makes it possible to locate the ancient forests and classify the most frequent species. Some of these snails belong to more modern ages, but they range from the Capesian civilisation to the Neolithic cultures of the last millennium, which merge with historical times. Some of the deposits are large, according to Lionel Balout: “under the immense great wall of Relilai, 5,000 metres of ashes represent some 500,000 m3 of charred wood and the whole of the Tlidjsene depression, southwest of Tébessa (south of Constantine), has many similar deposits in refuges and caves.”
Although there is enough evidence to admit a recent climatic change in North Africa, we are not aware of any work that allows us to establish approximate dates of successive changes in the vegetation in this area. But we can provide the following data: Mr. Picq, a meteorologist who lived in the Sahara observatories, has informed us that there is a silicification front of plant species that extends into the south of the central Sahara, in regions north of the Niger. On the banks of the river a characteristic flora develops, but if you go north you find hardwood forests, beyond which the silicification process appears. Dead and dried out trees that stand upright are watered by the silica contained in the wind that penetrates the wood, converting the trunk into a monolith. Further north, they are found blown over by the wind and scattered in the ground in broken pieces as large stones. Even further away, they are found in smaller pieces with which the natives make handles for their knives. This is the same phenomenon that Kropotkin observed in Turkestan. This process of silicification, spread out over such a large distance, indicates a precise mode of drying out of these places at dates not very far in the past, a drying out that was also rapid. The existence of stout species in the Sahara has recently been confirmed by direct observation: there are still conifers in the central desert. An expedition led by the archaeologist Henri Lothe in 1950 to copy rock paintings in the Tassili discovered cypress trees (cupressus dupreziana) in Tamrit “whose trunks measure 6 metres in circumference! The cypresses that were uncovered in front of us are one of the most singular curiosities of the desert… We had never seen this species in the region. The guide explained to me that there are many trees in the neighbouring mountains that died a long time ago. They also come from prehistoric times, and are the rare witnesses of a more humid past. …. There are about a hundred of them left, but the inventory we made tells us that they were numerous at the top of the Tassili… Thus, the Hoggar and the Tassili once enjoyed a Mediterranean climate and therefore it would not be surprising if these mountains had been populated.”
Oued Saoura floods: Springs once bathed the Sahara until historical times
It has already been suggested earlier that the Western Sahara is characterised by the presence of a fluvial network of dead rivers, the morphology of which can still be clearly distinguished today. Some of these wadis were very important, and once carried large masses of water. The Oued Saoura descends from the Moroccan Atlas and extends up to 500 or 600 km towards the centre of the Sahara. But as the water that flows through it only lasts a few days in the year, it is obvious that it is not this force that has dug the bed of this normally dry river. It is the same thing with another wadi, the Igargar, this one already fossilized, which had in the past impressive dimensions, of which Emile Félix Gauthier made his description. “Its source was in the tropics and its last basin was near Biskra (in the north-east of Algeria): a thousand kilometres as the crow flies; an intermediate length between the Danube and the Rhine. The Igargar flowed from south to north, from the heart of the desert to its periphery; exactly the opposite of the Wadi Saoura… The consequences of this fact are considerable.
This can only be explained by the presence, in the past, of significant rainfall in the central regions of the Sahara, the waters of which fed a large river that had carved out valleys and formed an immense river network. Thus, the Igargar ran parallel to the Nile, but the Igargar was narrower and its source was in an area that later became a desert. In contrast, the two sources of the Nile that feed it are in the heart of the equatorial zone. Two natural reserves of enormous capacity, located in regions that are irrigated at certain times of the year by extraordinary rainfall. For this reason, the Nile has remained alive while the Igargar has fossilised.
Several witnesses, fish and other zoological witnesses, confirm that the decline and death of these ancient great rivers took place at a recent date, according to Gauthier: “It is not only its juvenile forms that testify to the fact that the waters of the dead valleys of the Igargar have flowed at recent dates. For a long time now, small tropical fishes, the chromis, have been known in Biskra in the oases of the oued Rir, i.e. the last basin of the Igargar Quaternary. They abound nowadays in the ponds and canals of the palm groves. They have been seen to emerge from the wells, and to take refuge where they can in underground springs. Recently, in the same region, a much larger fish was found, the Clarias lazera, a catfish popularly called by the English and French, “poisson chat”. In the past, it was a tropical fish that still thrives in Egypt along the Nile, but it is an intruder in the Mediterranean world. In the Algerian Sahara it is found all along the Igargar, from the lagoons where it once disappeared, to its sources in muddy pools where it lives precariously. In the same region of Biskra, a companion of its more famous fish dances: Cleopatra’s asp, the snake of charmers, a cobra from Hindustan, which has also emigrated from the tropics. Its presence in southern Algeria remains inexplicable if one does not involve the Igargar of the Quaternary. The fact becomes even more obvious with the crocodile. It was found in pools of the Oued Mihero, an artery of the Igargar. It may be the last survivor, and one has to imagine the biological miracle of this animal surviving in such an environment, but it is an undeniable reality. All of this leads us to a time when the Igargar and the Taj asaset wadi meet at their sources, establishing a communication by water between the tropics and the Mediterranean world. This time cannot go very far back in time, because if the rivers died, some of its fauna survived.
When was this event? The terms of the question need to be set. Was it a great Saharan river that flowed majestically through its valley, like the Danube today, that managed to carve its bed violently into the rock? This case can be traced back to geological ages. We are more interested here in the last features of the Igargar, when it resembled the rivers of the Mediterranean basin, without having deserved to be called a wadi. With the data we have on its residual fauna, it is very likely that its long agony lasted until recent, i.e. historical times.
According to Lothe, there is in Tassili, a mountainous region in the centre of the Sahara, a small oasis, Iherir, “which is the richest place in the desert in terms of water, a fact that is inconceivable in other places, the lakes follow one another without interruption in the bed of the wadi (perhaps a tributary of the ancient Igargar), some of them reaching a kilometre in length and 10 or 12 metres in depth. During the first French expedition to the Tassili in 1905, Captain Touchard, warned of the presence of the last great saurians of the Sahara thanks to the traces that these animals had left. Two years later, one of them was killed by a subordinate of Captain Niegen and dissected to decorate the zoology laboratory of the University of Algiers. The last specimen was killed in 1924 by Lieutenant Bauval. During his expedition in 1950, Henri Lothe was unable to discover one despite numerous searches. Due to a lack of food, this species had become extinct, and with the drying up of the country, the fauna had disappeared little by little, along with the crocodile, a voracious carnivore. As Lothe rightly said, “it is a magnificent testimony to the humid past of the Sahara, at a time when a very extensive river network crossed it from north to south, linking the fauna of the salt lagoons (chotts) of Barbarie with those of Niger and Chad. There is no doubt that the presence of these reptiles confirms that the date of the drying up of the Sahara does not go back very far in time, for the simple reason that this witness could not have lived much longer after the disappearance of its natural environmental setting.
These last vestiges of a humid environment survived in the Tassili because of its altitude. But what about the plains of the Sahara? Another fact is that there are large aquifers under the wadis. To reach this water, the natives built wells and tunnels. These underground galleries were the object of considerable work, spacious, one person can walk through them, and sometimes reach 70 metres in depth. They have ventilation shafts and their dimensions are considerable, according to Gauthier, in the Tamentit, these galleries measure 40 km. These works could not have begun when the water levels were at great depth, as would have been the case if the climatic and fluvial regime had changed in remote times. Since the natives do not have the technical means to discover them underground, the construction of the wells and galleries began when the water was on the surface. And as the climate worsened, they began to dig the ground in synchrony with the decrease in water, and went down as the drought increased. These works are recent, according to some historical accounts the oases were created during the Christian era, between the 6th and 18th centuries. According to Gauthier, the oldest are those of Gourara: “In the Touat, the oriental irrigation procedures, the galleries, i.e. the palm groves as they exist today, date from the 3rd century of the Hegira, our 10th century after Jesus Christ. In the Tidikelt, the oldest palm groves do not date further back than the 13th century, and the most recent ones date from the 18th century.
The Clarias Lazera: The toponymy of the Sahara bears witness to a recently inhabited region
As Emile Félix Gauthier might say, the Central Sahara is still not “aseptic”. This region no longer has the life of yesteryear, but still has the memory of it; and all its explorers agree on the following fact: these areas of the desert were once inhabited, up to the dreaded Tanezrouft. Evidence of ancient populations can be found everywhere on the ground, and in certain privileged places, evidence of a troglodyte life, where engravings and cave paintings abound. These works show not only the demographic density of these regions, which are now deserted, but also the fauna and flora that have disappeared. In the middle of the Erg, in the Ténéré, i.e. the driest region of the Sahara today, Lhote found the remains of fishermen’s camps, several mounds of fish bones “that could fill several carts”. Scattered on the ground, in the Tanezrouft as in the Rio de Oro, are rollers or large mortars cut in stone in one piece. There is no doubt that they were used to flatten the grain and reduce it to flour. These instruments are similar to those still used in Sudan, but are always found in places where there is no vegetation whatsoever.
The current toponymy of the Central Sahara shows that these places were inhabited by populations, and abandoned at recent dates. In a true “aseptic” desert, so to speak ancient, there is no toponymy. As no one has passed through these places for hundreds of years, or even thousands, the ancient geographical names, if they existed, have been forgotten. Because of this lack, the explorers of these areas were forced to name the high points of the terrain with their knowledge and understanding. This did not happen in the Central and Western Sahara; on the contrary, the traveller is surprised by the abundance of names given in the guidebooks. How can this wealth of names be explained in places so far from any urban concentration? It must be admitted that at other times, a large population had given names to the various high points, and that its disappearance is recent because the toponymy has remained in memory, and has come to us through the caravans.
To ensure their orientation, the guides had every interest in keeping them in memory, and this tradition has been maintained from father to son. This cannot be very old. As the adverse conditions of the Sahara increased, the passage of caravans decreased. It is known, for example, that in modern times, during the sixteenth century, they crossed the central desert assiduously, from southern Tunisia to Timbuktu, sometimes consisting of several thousand camels. It is not only maritime trade that has reduced this traffic, but also the ever-increasing risks caused by the climate, which has reduced its importance. The fact is that when the Europeans started to explore the Sahara, the number of caravans was already at its minimum. In other words, if the Europeans had not intervened with their technical means, the toponymy of the Central Sahara would also have disappeared. But the existence of this toponymy confirms this recent depopulation, the consequence of a climatic crisis.
A brief chronological reconstruction of the historical degradation of the Central Sahara
The historical sources demonstrating a historical climate in North Africa, different from the current one, are already presented in “When North Africa was not yet entirely desert”.
With the dendrochronological and geographical elements, the zoological and biological elements, the historical and archaeological evidence mentioned, a small chronology of the climate of the Central Sahara can be drawn up:
11th century BC: The central regions of the Western Sahara had a green appearance, typical of a grassland environment. If this is the case, the region was irrigated by 800 millilitres of water per year.
6th century BC: During the time of Herodotus, some areas of the Central Sahara retained their former character, while others began to deteriorate. Water may have been falling at the rate of 600 millilitres per year, which was already unevenly distributed during the summer
1st century BC: During the time of Strabo, the process of drought was much more advanced. An arid facies was already reached, with perhaps parts of the Central Sahara still sub-arid. To cross these regions on horseback it is necessary to take precautions.
3rd century AD: A rapid mutation of the North African fauna can be noticed. Most of the central Sahara has a sub-arid facies with a rainfall of around 250 millilitres of water per year.
6th to 8th century: The xerophilous steppe, the antechamber of the desert, appears throughout the Central Sahara.
11th century: The sub-arid facies reached the confines of the Mauritanian Atlantic
The drying out of the Sahara due to its enormous dimensions and the excessive nature of its radiation, the work of correlation laws that unify the most diverse geographical frameworks, coincided with climatic disturbances in the environmental framework of the Iberian Peninsula.
This also allows us to understand and correctly interpret the rare and laconic texts that have come down to us. As we will see, when we analyse the revolutionary crisis that took place in Spain at the beginning of the 18th century, one author informs us that hunger had eradicated half the population, and we are not prepared to consider this proportion as the result of the hyperbolic genius of the ancients. It will then be possible to fit this data into a more far-reaching phenomenon: the transformation of the landscape had ruined the country’s traditional agriculture.
On the other hand, an observation is in order: a notable convergence between the development of strong ideas and the modification of the environmental framework, which was probably not the only one in our history; the accentuation of the drought from Asia to Africa during the High Middle Ages was a parallel phenomenon with a divergence in monotheistic ideas that was simultaneously manifested in these regions. It was the fruit of a long previous evolution, and quickly reached considerable proportions and dimensions: Islam, and the Arab civilisation.
To be continued…
When History becomes a fable 1: The incredible great Muslim military conquest –
When History Becomes Fable 2: Analysis of available Sources
WHEN HISTORY BECOMES A FABLE 3: The Riddles of Islamic Expansion
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