by Brian Fagan
The Indian summer monsoon arrives in June as the land absorbs heat from the sun faster than the ocean does. Air masses over the land heat up, expand, and rise. As the air rises, cooler, moister, and heavier air from the ocean replaces it. The winds shift to the southwest, blowing inshore, bringing heavy rainfall. Central and western India and Pakistan receive more than 90 percent of their rainfall during the three months of the summer monsoon. The south and northwest receive 50 percent to 75 percent of their annual totals from the monsoon. In the semiarid regions of South Asia, the fluctuations of monsoon rainfall can make the difference between life and death. Very often, however, it’s not a lack of rainfall that is the problem, but the rain’s timing. A monsoon season may start with a deluge; then no more rain may fall for the rest of the year. India is a high-risk environment for farmers, as is northern China (described in chapter 12).
A thousand years ago, India was a patchwork of forest and irregularly cleared lands. Political events or war could result in the complete abandonment of large areas of once cultivated land, which became open reaches of grassland. Thousands of years of human interference had devastated the natural vegetation. For example, had farmers not cleared brush and set fires, much of the western coastal region would have been covered with tropical evergreen forest or dry tropical deciduous or thorn woodland. In 1837, the British surveyor W. H. Sykes wrote of the countryside around Mumbai (Bombay) that during the dry months of April and May “the country appears an arid desert. After the monsoon however . . . the country appears one great field of grain.”15 To survive as a farmer in an environment of such contrasts, where intense heat ravaged the land for months on end and most rain fell within the compass of a few months, required patience and adaptability, also mobility.
As so often happens, we know nothing of the fortunes of the millions of farmers who labored, throughout the warm centuries, in the shadow of nomad raids and indiscriminate plundering. Their settlements have long vanished, many buried under deep accumulations of river silt. As happened everywhere, droughts and floods were ignored in the chronicles of the day. This is hardly surprising, for the warm centuries were a time of considerable upheaval. While Europe was entering the High Middle Ages and the Maya wrestled with drought, India was encountering Islam. The commander of the first Muslim army to reach semiarid Sind, in what is now Pakistan, was not impressed. He reported that “water is scarce, the fruits are poor, and the robbers are bold; if a few troops are sent they will be slain, if many, they will starve.”16 For centuries, raids in search of plunder, especially from the Ghazni kingdom in Afghanistan, ravaged India. The plundered wealth from these incursions turned Ghazni into a great center of Islamic learning during the eleventh century. Inevitably, raiding led to conquest in the end. After 1206, Muslim dynasties ruled from Delhi for 320 years. The sultan Shams-ud-din, who ruled from 1211 to 1236, was able to keep Ginghis Khan at bay through consummate diplomacy.
These events unfolded at a time of prolonged cool and La Niña–like conditions in the southwestern Pacific, which would have led to good monsoon rainfall most years. No farmer could relax, however, for droughts could descend for several years without warning, as a result of ENSO shifts in the southwestern Pacific, before cooler conditions there brought plentiful monsoon rains once again. For this reason, there must have been occasional serious, and long forgotten, periods of drought-caused hunger. We have only the testimony of later centuries to inform us.
Even after the warm centuries, crop failures plagued India. Before railroads and improved communications made prompt grain shipments possible, famine was endemic. In 1344–45, such a severe famine affected India that even royalty starved. Writing of northern India, the sixteenth-century Mughal emperor Babur wrote that villages and even towns were “depopulated and set up in a moment! If the people of a large town, one inhabited for years even, flee from it, they do it in a way that not a sign or trace of them remains in a day or a day and a half. On the other hand, if they fix their eyes upon a place in which to settle, they need not dig water-courses, or construct dams because their crops are all rain-grown.”17 The failure of the monsoon rains in 1629 and again in 1630 depopulated entire rural districts. Millions of people and their cattle perished. Cholera epidemics carried away entire villages. Another major drought came in 1685–88. A century later, the great hunger of 1770 depopulated and ravaged a third of Bengal. The South Asian monsoon failed again in 1789, and the failure was followed by intense droughts that descended on Australia, Mexico, and southern Africa in 1790. Six hundred thousand people starved to death in the northern Madras region in 1792. The dead and dying blocked the streets of Calcutta. One reason for the high casualty rates: until the eighteenth century, most of India relied on high-risk “dry” agriculture. Irrigation works did not become commonplace except near permanent rivers until the eighteenth century.
THE MONSOON ALSO played an important role in the flamboyant Khmer civilization of Southeast Asia. Funan was the medieval Chinese name for the lower Mekong River. Its delta was a land of wealthy kingdoms and settlements surrounded by high earthworks, where the Chinese obtained bronze, gold, and spices.18 By the beginning of the warm centuries, the center of political and economic power had moved upstream to the Tonle Sap, the central basin of Cambodia. Tonle Sap (“Large Freshwater Lake”) is a large shallow lake during the dry season covering about 1,150 square miles (3,000 square kilometers) and some 40 miles (66 kilometers) long. A river of the same name connects the lake with the Mekong. During the monsoon rains between August and October, so much floodwater pours into the Mekong that the river reverses its flow and backs up into the Tonle Sap. The lake swells rapidly, flooding surrounding fields and forests, and eventually covering as much as 6,200 square miles (16,000 square kilometers) with depths up to 30 feet (9 meters). The Tonle Sap is now between 80 and 120 miles (133 to 167 kilometers) long and up to 30 miles (50 kilometers) wide. The fish from the Tonle Sap breed in the flooded forests along the edge of the lake. Many of them swim out through the outflow into the Mekong. Late in October, the floodwaters slowly retreat, trapping millions of fish in muddy bayous. The Tonle Sap’s bountiful environment was a paradise for rice farmers and generated enough food to support a glittering, wealthy civilization—provided the local rulers built water control systems and thereafter managed water supplies.
Tonle Sap was a cockpit of competing lords and internecine warfare for many centuries. But in A.D. 802 a dynamic Khmer monarch, Jayavarman II, defeated his competitors and carved out the Angkor state, held together by Hindu beliefs, plus force and tribute payments. Jayavarman consolidated his kingdom by proclaiming himself a god-king; his subjects worshipped him as a deity. All the resources of an increasingly centralized government were devoted to the cult of the divine monarch. Everyone, whether general, noble, priest, or commoner, was expected to subordinate his or her ambitions to the need to perpetuate the existence of the king on earth and his identity with the god in this life and next. Jayavarman II ruled for forty-five years, the first of at least three dynasties of Khmer kings who presided over a state that reached the height of its prosperity during the ample monsoons between A.D. 900 and 1200, the Medieval Warm Period.
Jayavarman II and his successors presented themselves as reincarnations of the Hindu creator god Siva: the varman, or protector. Under them, a tightly controlled bureaucracy of high-status families supervised every aspect of Khmer life and owned land farmed by others. Local agriculture produced large enough food surpluses to support an immense and long process of temple building. During the dry months, the entire kingdom devoted itself to building ever more splendid palaces and temples constructed on artificial mounds in the hub of the Khmer universe, an area known today as Angkor.
The temples of the Khmer rulers dwarf those of Egyptian pharaohs or Maya lords. Four years after his accession in 1113, King Suryavarman II commenced building Angkor Wat, a masterpiece of beauty, wonder, and magnificence. Every detail of this extraordinary structure reproduces part of the hea
venly world in a terrestrial mode—a central continent known as Jambudvipa, with Meru, the cosmic mountain, rising from its center, the highest tower at Angkor Wat. Four lesser towers represent Meru’s lesser peaks, the enclosure wall depicting the mountain at the edge of the world; the exterior moat, the ocean beyond. Yards of superb bas-reliefs depict Suryavarman receiving officials, progressing through a forest on an elephant accompanied by heavily armed soldiers. Celestial maidens, slender and sensuous, dance with the promise of the delights of paradise.
A later monarch, Jayavarman VII, erected a huge new capital at nearby Angkor Thom in 1181. He and his immediate successors continued to spend without constraint. He dedicated the Ta Proehm temple to his mother. An inscription recorded that about twelve thousand people worked for the temple, living off rice grown by sixty-six thousand farmers, an indication of the scale of effort that went into maintaining what can only be described as a weirdly centripetal kingdom. In every preindustrial civilization, like, for instance, those of the Egyptians and the Maya, everything flowed to the center, for the rulers controlled the labor of the ruled. The Khmer empire was an extreme example of such centralization, for everybody and everything was devoted to the divine king and his celestial immortality. Khmer rulers collected taxes in labor and grain, imposed tribute, and annexed the labor of their subjects to build their stupendous temples, whatever the cost. As a result, their centripetal domains lived on the knife-edge of sustainability.
The kingdom balanced on a carefully engineered water system fed by the annual monsoon rains.19 The floodwaters helped rice production along the edge of the lake, but the water management network controlled water coming from the hills, as well as from the heavens. Angkor Wat and other Khmer temples mesmerize archaeologist and tourist alike, but it is only in recent years that scientists have gained a comprehensive and detailed picture of the stupendous waterworks that supported Khmer civilization. Angkor’s kings and their lavish works depended on huge rice yields sustained throughout the year; these in turn required enormous amounts of water and extensive irrigation systems. A radar shot from the space shuttle Endeavour in 1994 revealed segments of the so-called Great North Canal that moved water from the northern hills to two reservoirs (see sidebar). Today, an international team of researchers, headed by Roland Fletcher, Christophe Pottier, and others, is using more NASA radar images, state-of-the-art GPS technology, and even an ultralight aircraft, to map Angkor’s huge artificial landscape of dwellings and water tanks, once connected by small roads and canals, which extends over about 386 square miles (1,000 square kilometers). Three great reservoirs, or barays, stilled and stored the waters of three rivers, then diverted it, as required, for the ceremonial pools and storage facilities of the great temples, and also through canals to irrigated fields in the southern half of Angkor, and also as a way of stemming floodwaters. The reservoirs would have supplied enough water to support between 100,000 and 200,000 people, out of an estimated population of about 750,000. Most Khmer lived off independent rice paddies that captured water during the monsoons. But the barays filled one important function: they would store water that could be used in poor harvest years.
Archaeology from Space
Satellite photography and related imagery provide fascinating perspectives on the past from space. These technologies are especially useful for studying ancient land use and to locate specific features like fortifications, long-abandoned irrigation canals, and reservoirs. A number of different instruments can scan the electromagnetic spectrum emitted from the earth’s surface. The thermal infrared multispectral scanner (TIMS) uses a six-channel scanner to measure thermal radiation on the ground with great accuracy. The temperatures of soils and other sediments are of course invisible to the human eye, but so easily recorded by TIMS that minor differences in soil texture and moisture have revealed ancient field systems and roads masked by vegetation in the Maya lowlands. The images, with their overhead view, provided vital information on the intensive farming of the rainforest environment by Maya farmers, which could never be detected on the ground.
Synthetic aperture radar (SAR) beams energy waves to the earth’s surface, which provide returning signals that reflect long-forgotten features on the ground. SAR is especially useful for detecting linear and geometric features, such as the canals, reservoirs, and roads that surround Angkor Wat detected by the space shuttle Columbia in 1981. Satellite instruments can even be programmed to detect specific kinds of features such as canals. Over the Sahara Desert, Columbia traced long-hidden watercourses and buried valleys in the heart of the desert. When geologists investigated on the ground and dug into the hidden defiles, they were astounded to recover 200,000-year-old stone axes dating from a time when the Sahara was better watered than today.
Satellite imagery from space is expensive, but it provides unique, and often unexpected, perspectives on human exploitation of the landscape on a much larger scale than one might expect. The Ances- tral Pueblo of Chaco Canyon, New Mexico, built an elaborate road network that converged on the canyon. No one realized how extensive the road system was until satellite photographs revealed more than 370 miles (600 kilometers) of incomplete road segments, largely invisible except from space. The purpose of this road network remains a complete mystery, for the roads were not “highways” in the western sense, with clear destinations. They probably had a role in defining a now forgotten symbolic landscape.
The Angkorian empire was in decline by the fifteenth century, and urban Angkor itself was abandoned by the end of the sixteenth. Quite why remains the subject of vigorous controversy. Did trade routes shift away from Angkor? Had the temple-building monarchs bankrupted an exhausted kingdom? Did the rising influence of Buddhism eclipse the influence of Hindu god-kings? Most likely, a precipitous decline in crop yields was a decisive factor. Rising silt levels in canals during the dry season may have choked water supplies, the result of soil erosion resulting from widespread deforestation. Today, and as a result, the main river is now more than 16 feet (5 meters) below the ancient ground surface. The Greater Angkor Project, led by Roland Fletcher, is studying the canals and spillways. Fletcher argues that Angkor’s water management system became ever more complex as the sprawling civilization grew. Over many generations, the system became too elaborate, so huge that it could never be completely overhauled to compensate for the extremes of flood and drought that are inevitable in a monsoon zone. The Khmer created a fragile, totally artificial environment that was ultimately as unsustainable as it was magnificent.
As long as cool and La Niña–like conditions prevailed, summer monsoons brought good rains, but, as the Medieval Warm Period gave way to the Little Ice Age, climatic conditions may have become more volatile, with a higher incidence of El Niños and droughts. And the overtaxed water management system of Angkor would have been unable to supply the insatiable demands of god-kings. The collapse would not have come at once, but as a slow death when the people gradually dispersed into smaller settlements. The architectural masterpieces of Angkor were left as desolate as the empty Maya water mountains of the Yucatán.
CHAPTER 12
China’s Sorrow
Disorder, like a swelling flood, spreads over the whole empire, and who is he that will change its state for you?
—Confucius, Analects1
THE HUANG HE BASIN, NORTHERN China, late winter, A.D. 950. The wind cuts through one’s clothing, chilling one to the bone and gumming up one’s eyes. Oblivious to the cold and the fine dust, the farmers toil over their arid plots of land, thick cloths sheltering their faces. They turn over the soil, breaking up sods of earth hour after hour with never a break. The men move slowly, deliberately, stoically, as if knowing that their efforts are in vain. Last year’s millet harvest was far less than usual after a hot, unusually arid summer. People have been dying of hunger and dysentery for months, but the winds never relent, the skies are gray, the endless dust accumulates pitilessly on the freshly turned, arid soil. One of the farmers looks wearily up at the glo
om overhead, looking vainly for even a hint of spring rain. There is more hunger ahead.
They call the Huang He (Yellow River) “China’s Sorrow” because it has killed millions of people with its sudden floods and lengthy droughts. Few rivers are more prone to disaster than the Sorrow, at 3,395 miles (5,464 kilometers) China’s second longest river after the Yangtze. The Huang He rises in the Kunlun Mountains south of the Gobi Desert, flows through some deep gorges, then across the Ordos Desert before emerging into a huge drainage basin carved out of extensive plains covered with the fine, windblown dust known to geologists as loess.2 Here the great river picks up a heavy load of fine silt which turns its water a distinctive yellow. Eighty-seven miles (150 kilometers) from the mazelike channels of the mouth, the silt load exceeds that of every river in the world except the Ganges-Brahmaputra and the Amazon. With irregular monsoon rainfall and savage droughts, the 334,000 square miles (865,000 square kilometers) of the Huang He basin have been a crucible for human misery for more than seven thousand years. Here, global climatic forces helped decide the fate of medieval Chinese societies.
Map showing locations and peoples mentioned in this chapter. Some minor places are omitted for clarity.
IN NORTHERN CHINA, the monsoon and the forces that drove it shape the climate of the warm centuries. As always, the climatic record of the warm centuries comes, for the most part, from proxies. The documentary record is long. For more than a thousand years, Japanese and Korean officials have recorded the date of cherry trees’ spring flowering, a historical record whose duration rivals the longest from Europe. By combining archives such as these with proxies, Chinese climatologists have developed a winter temperature curve for eastern China, which shows that readings were above the long-term mean from A.D. 950 to 1300.3 The Medieval Warm Period was reality here. But, as always in East Asia, the major climatic player during these four centuries was the monsoon, nurtured in the Pacific Hot Pool.