by Brian Fagan
DROUGHTS ON THE steppe are usually caused by persistent high-pressure systems over the Arctic. These systems, which can remain stationary for long periods, prevent the passage of the usual rain-bearing frontal systems and draw in intensely cold, dry air from northern seas. The fresh Arctic air enhances dry conditions. In 1972, for example, an anticyclone centered over Moscow persisted throughout the summer, blocking the passage of Atlantic depressions. Extremely hot, near-desertlike conditions in regions like the Volga and Ukraine cut summer rainfall to 20 or 30 percent of the average and resulted in very low relative humidity. Temperatures were 1.5 to 3.5 degrees F (3 to 7 degrees C) above the norm; the heat sucked such moisture as remained from the ground. Without doubt, similar intense droughts occurred in earlier centuries.
The medieval nomads were well aware of climatic variations from year to year. Long, snowy winters denuded pastures of their grass. Precious winter feed had to be stretched for an extra two months or more, being doled out in ever smaller quantities. Oxen and cattle subsisted off bedding grass and lost weight. Some became so weak that the herders had to help them rise. Calving losses rose sharply. Emaciated beasts perished of cold or were lost in the deep snow. In particularly cold winters, both animals and humans died in large numbers.
When the summer did come, it would arrive suddenly. The snow would melt rapidly, turning the plains into a quagmire, swelling streams, and impeding movements to summer grazing grounds. Soaring temperatures meant that little water percolated into the soil, grass growth was weak, and the summer graze was, at best, poor. The only protection against such disasters was movement. In the central regions of the steppe, the nomads traveled as far south as they could during the cold months to ensure that their grazing grounds were denuded of grass for the shortest possible time. In the summer, they moved far north to strategic, sheltered river valleys, areas where rainfall was slightly more plentiful and grass of better quality.
Water and its distribution across the landscape were also critical variables. Each tribe defined its territory around river systems, especially the sunken river valleys incised into the steppe that were the linear sinews of their territory. Nomads would winter in houses built at valley elevations below the level of the plain, then migrate northward in spring, sometimes as early as February or March in mild years, or as late as May in cold ones. The seasonal movement northward would stop and start, depending on local grazing and sometimes impeded by swollen streams. Eventually, their animals were allowed to graze on rich pasture, which might cover as much as 3,250 square miles (about 8,400 square kilometers). In mild years, people would sow grain, then neglect it until they were about to move south. In dry and cold years, they would have no chance to plant, for they would arrive at the summer grazing too late to sow, with too little time before cold weather killed the growing crop.
Each temperature change and rainfall shift dramatically altered the relationship between the nomads and their environment. Drier periods, with their life-threatening droughts, brought stunted pasture, decimated herds, extended searches for grass and water, and inevitable, often violent encroachment into neighbors’ territories. In better-watered cycles, herds increased, the carrying capacity of the grazing land was much improved, and territories shrank, with a resulting decrease in warfare. For centuries, those living on the fringes of the steppe lived in fear of the fierce nomads, who would arrive without warning and create mayhem as they sought better pasture.
UNFORTUNATELY, THE EVIDENCE from climatic proxies that would enable us to identify the climatic fluctuations of Ginghis Khan’s day is scant. Climate records extending back a thousand years are the Rosetta stones of paleoclimatology, rare chronicles treated with the scientific reverence they deserve, even if they are only proxies, indirect traces of ancient temperature and rainfall. Such sequences are rare treasures for archaeologists and historians seeking decadal and century-long climatic fluctuations like the Medieval Warm Period. As we have seen, the bolder among climatologists have combined these records into large-scale temperature reconstructions going back as much as a millennium. These portraits of past climate come, for the most part, from tree-ring records, historical documents, and instrument readings over the past century or more. But with respect to the climate on the Eurasian steppes at the time when Ginghis Khan embarked on his murderous campaigns, the record is still almost blank, except for broad generalizations and just one or two tree-ring sequences.
A research team from the Tree-Ring Laboratory at the Lamont-Doherty Earth Observatory in Palisades, New York, and the National University of Mongolia collected samples from living five-hundred-year-old Siberian pines at Solongotyn Davaa (otherwise known as Sol Dav), a location high in the Tarvagatay Mountains of west-central Mongolia.18 The ecological conditions at this site are such that tree growth is influenced by temperature changes from one year to the next. After months of research, the team developed a temperature curve from living trees for the years 1465–1994. Then they returned for additional samples from well-preserved, long-dead wood, linking the tree rings from these fragments with those from the living pines. The expanded climatic sequence now extends back to A.D. 850 and, less reliably, as far back as A.D. 256, to the time when Rome was all-powerful and the Scythians flourished on the Eurasian steppes.
The Sol Dav leaves us in no doubt of today’s warm temperatures, with the highest tree-growth rates coming between 1900 and 1999. But there are notable earlier periods of warmth around A.D. 800. The year 816 was the warmest in the entire sequence, even warmer than today, although 1999 was the warmest year over the past millennium. The warm cycle of the ninth century and another in the early 1400s bracket the centuries of the Medieval Warm Period. There was a period of colder conditions around 1100, so the warming was not monolithic. The cooling of the Little Ice Age ensued, five centuries of unpredictable cooling and warming that climaxed with very cold conditions during the nineteenth century.
Not only does the Sol Dav sequence provide evidence of medieval warming, but also its fluctuations coincide with temperature changes over at least the past four centuries recorded in the well-known Mann sequence for northern and western Europe already described in chapter 1. The well-preserved ancient pines of Mongolia place Ginghis Khan’s conquests within an extended warm period during which frequent droughts may have wreaked havoc on steppe pastures in a world where people depended on horses as well as stock of all kinds. If the solitary Mongolian tree-ring sequence is a reliable barometer of the cyclical temperature and rainfall of the Great Khan’s time—and there is every reason to believe that it is—then it’s clear that the climatic pump of the steppes acted as it had for thousands of years, putting nomads and their restless movements into play on the steppe and bringing them into conflict with their neighbors to the south. The difference was that Ginghis Khan rose to power at a time when drier conditions shrank pasturage on the steppe. This was nothing new; but now, a brilliant leader succeeded in forging great armies of conquest from a maze of competing tribes and independent-minded chiefs. The Flail of God shook Asia and Europe to their foundations.
THE PROLONGED WARM period detected in the Mongolian tree rings coincides with Ginghis Khan’s savage conquests: hotter and drier conditions would have meant a surge in warfare at a time of potential hunger and rising unrest. Ginghis Khan’s incursions into China and his merciless smashing of the Seljuk Turks’ Khwarezmid empire in central Asia in 1220 and 1221 brought the Mongols deep into settled lands.
Shortly before his death, in 1227, Ginghis Khan told his sons: “With Heaven’s aid I have conquered for you a huge empire. But my life is too short to achieve the conquest of the world. That task is left for you.”19 The conquests continued after Ginghis was gone. One of his sons, Ögötai Khan, extended the empire westward in 1236. Batu, a grandson of Ginghis, soon conquered the Crimea, then ravaged what is now Bulgaria as well as fourteen Russian cities, turning their shattered remnants into vassal states. Next he turned his attention to Europe, with the objective of reaching
“the ultimate sea.” The Mongols under General Subutai divided into three groups, conquered Poland and Hungary, and swept into Austria, where they prepared for a probe into the heart of Europe in 1241. At that moment, Ögötai Khan died. Batu Khan was a potential candidate for Great Khan, so he withdrew his forces to the steppes. In the event, he was not chosen and devoted his efforts to consolidating his conquests around the Urals. He held sway over the Cuman steppes and over various Russian kingdoms and never returned to the scene of his former conquests.
BATU KHAN’S WITHDRAWAL coincided with the return of cooler, wetter conditions, which brought improved pasturage to the steppes. His kingdom flourished during generations of good pasturage, when warfare died down. Although Batu always maintained ambitions of returning west, good grazing conditions at home allowed his people to pasture a huge territory from the Volga–Don to Bulgaria. There were no incentives for ambitious conquests when grazing was plentiful and trade flourished with lands to the south.
But what would have happened if the climatic pendulum had not swung, and if droughts had intensified on the steppe? To judge from earlier centuries, warfare and restless movement would have continued, and, almost certainly, Batu Khan and his generals would have returned to the west. His spies had already given him a clear picture of the kingdoms that confronted them, and of their armies with their heavily armored knights, who had proved no match for Mongolian archers and horsemen. He would have followed his original plans, drawn up with General Subutai: invade Austria and destroy Vienna first, then move against the German principalities before turning his attention to Italy. If all went well, he would then have marched into France and Spain. Within a few years, perhaps as early as 1250, Europe would have become part of a huge western Mongolian empire.20
Would this have actually occurred? The Mongols had already defeated formidable European armies in decisive, bitterly fought battles on the Hungarian plain, where thousands had perished. That tales of their ruthless conquests and indiscriminate slaughter had preceded them would have given them a major psychological advantage in a Europe riven by factionalism and chronic rivalries. By the time Batu had mastered Europe, the Mongols would have accumulated a vast experience not only of conquest, but also of assimilating themselves with, and accommodating, other cultures and religions. If central Asian history is any guide, European civilization would have continued to flourish as the new conquerors became absorbed into its fabric.
But fascinating questions arise. Would Europe have become a Muslim continent, or would the Mongols, who were tolerant of other beliefs, have left the Catholic church alone? Had the conquest taken hold, would there have been incentives for European explorers and merchants to find new ways to tap the riches of Asia by opening new seaways across the Atlantic and round the Cape of Good Hope to India when they could have land routes across a unified empire? And what would have been the impact of the Mongols on Muslim Spain? Here one could expect the same process as happened in central Asia: an environment in which Islam flourished, and might even have expanded northward over the Pyrenees.
There would have been a point where the momentum of conquest slowed—perhaps when the conquerors reached the Atlantic, or perhaps earlier. Had the climatic pendulum not swung back, there would have been no incentive to return home to a drought-ridden, arid land. Nor would peace have descended on the steppes, where, under benign conditions and with ample pasturage, each summer the tribes moved from their winter quarters in the south near the Sea of Azov and Astrakhan-Serai to summer grazing on the banks of the Don and Oka rivers. For all the pull of the steppe and the nomadic life, the political and economic center of gravity of the Golden Horde’s empire would have moved west into better-watered, more settled lands. But, equally well, as happened to Ginghis Khan’s domains, the sheer size of the empire, corruption, and inefficient administration might have caused Europe to split up into a patchwork of states very different from those that witnessed the Renaissance and the Age of Discovery.
The ebb and flow of Mongol rule would have depended in part on the realities of nomad life, just as it had for thousands of years. When pasturage was good, there was peace; when the climate deteriorated and drought ravaged the steppes, warfare broke out and the people of the settled lands trembled in fear. The endless rhythms of warm and cold, plentiful rainfall and drought, ample grass and no forage were a major engine of history, as powerful in their way as economic changes, the ebb and flow of political intrigue, and the abilities of individual rulers. Ginghis Khan and his armies, and the smallest tribe on the great steppes, were affected by the same realities. When drought on the plains coincided with social unrest and brilliant generalship, the foundations of history shook. And had the droughts continued, European civilization might have a very different face today.
CHAPTER 4
The Golden Trade of the Moors
They start from a town called Sijilmassa . . . and travel in the desert as it were upon the sea, having guides to pilot them by the stars and rocks in the deserts.
—Anonymous, Toffut-al-Alabi (twelfth century)1
IN JULY 1324, THE SULTAN OF EGYPT welcomed a truly exotic visitor. Mansa Musa, ruler of the West African kingdom of Mali, was on a pilgrimage to Mecca. Hundreds of camels and slaves carried gold staffs and lavish gifts across the desert. Mansa Musa held court in Cairo for three months. To the Egyptians’ astonishment, his subjects prostrated themselves before him and poured dust on their heads. The Malians injected so much gold into the Egyptian economy that the value of this most precious of metals decreased between 10 and 25 percent for some years. Tales of the African kingdom and its fabulous wealth reverberated through the Christian and Muslim worlds. By the end of the fourteenth century, two thirds of Europe’s gold came from Mali, transported by camel across the Sahara. This “Golden Trade of the Moors” linked two very different worlds, those of the Mediterranean and of the western Sudan in West Africa, Bilad es-Soudan, what Islamic geographers called “the Land of the Blacks.”
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LIKE THE EURASIAN steppes, the Sahara Desert expands and contracts like a natural ecological pump. This, the southern margin of the medieval European world, is one of the hottest places on earth. Prevailing, dry northeasterly winds raise temperatures above 98 degrees F (37 degrees C) on more days of the year than anywhere else on earth. A dead environment, one might think, but the Sahara breathes, is never static. When rainfall increases by even a few millimeters, the desert’s margins shrink, sometimes by many miles. In warmer periods in the remote past, vast shallow lakes and semiarid grasslands, watered by seasonal rivers from arid mountain ranges, covered thousands of square miles of what is now desert. Only one significant lake remains. One hundred and twenty thou sand years ago, Lake Chad, on the southern boundaries of the desert, covered a larger area than Eurasia’s Caspian Sea. Today, Chad is drying up rapidly. During good rainfall years, the desert absorbs animals and people, often far north of Lake Chad. When drought years descend on the Sahara, water sources and grazing dry out, and the sparse desert populations move out to better-watered areas. The Saharan pump is never still; it is sometimes quiescent for a few years, then gyrates wildly during periods of highly variable rainfall from one year to the next. This is the story of the gold trade of a thousand years ago between the Islamic world and West Africa. The trade thrived through the warm centuries thanks to the highly adaptable camel and because those who handled the gold at the African end engineered their society to accommodate the sudden climatic extremes that marked the Medieval Warm Period.
Locations mentioned in this chapter as well as a general impression of desert caravan routes.
THE CLIMATIC HISTORY of the Sahara and the Sahel, the semiarid grasslands that border the southern margins of the desert, is a relentless chronicle of chaotic shifts, well documented from both modern instrument records and proxy measures from deep-sea cores drilled off Mauretania.2 We can even link some of these records to the deep-sea cores from the all-important Cariaco basin off V
enezuela, described in chapter 8.
The Mauretanian sea cores reveal recent, abrupt changes of 1.0 degree F or more (2.16 degrees C) in the sea surface temperatures of the eastern North Atlantic. At the same time, changes in the salinity of the ocean at different levels can affect the workings of the ocean conveyor belt that is a fundamental driver of global climate, transferring heat as it does from the tropics to northern latitudes. The sea surface temperature in the eastern North Atlantic has a strong effect on the dry winds that blow across the Sahara. If sea surface temperatures are lower in the eastern Atlantic between 10 degrees north and 25 degrees north, and higher in the Gulf of Guinea, the monsoon winds are displaced southward, causing drought in the Sahel and Sahara. We know this because between A.D. 1300 and 1900, cooling documented in the Mauretanian sea cores caused dry conditions in the Sahel, including droughts that may have been worse than the disastrous megadrought of the 1960s. The cores allow us to make a tentative reconstruction of climatic conditions over the past two thousand years, and through the Medieval Warm Period, that goes something like this:
Between 300 B.C. and about A.D. 300, conditions in West Africa were stable and dry—as they were in both Southeast Asia and the Amazon basin—with rainfall somewhat below modern levels. People moved into better-watered areas like the middle Niger, where towns appeared.
After A.D. 300, rainfall increased to perhaps 125 percent to 150 percent of today’s level until A.D. 700, a time when a formerly shrunken Lake Chad expanded dramatically. (There is no evidence of intervening dry periods, but they may yet be undetected.) Then, between A.D. 900 and 1100, there was an abrupt transition to much more unstable conditions, mirrored by increased monsoon variability in the Cariaco basin on the other side of the Atlantic. At some times there was high, stable rainfall; at others, drought. The Sahara’s margins were constantly on the move.
