The Great Warming
Page 16
For the Pueblo, movement was the only logical solution to the droughts of the warmer centuries. We know there was hunger and fighting for food and water. There is even evidence of ritual cannibalism. Fortunately, the ancient traditions kicked in and people adjusted by moving away, household by household. In some pueblos, large numbers of clay pots and stone tools, also heavy grinding stones, still lie where their owners left them. The strategy of movement was successful. Centuries later, the legacy of the Ancestral Pueblo thrives in vibrant oral traditions and ritual observances, in architectural and agricultural practices that resonate in the Southwest to this day. Despite all the trauma of the Spanish entrada and the upheavals wrought by industrial society, Pueblo communities are politically autonomous today, using ancient shared rituals to promote common identity and harmony. Chaco Canyon and other pueblos remain part of the ancestral memory of modern Pueblo societies, and visitors still go to breathe in the strength of the ancient places and their inhabitants.
There was no mass migration out of the Chaco, no one moment when the elders abandoned the great houses that were the focus of life in the canyon. The close deliberations took place in subterranean kivas around winter fires, also at home between husbands and wives as their hungry children slept. Perhaps several husbands would trek out from the canyon to visit relatives, to prepare the way for a move to somewhere where they would be welcome and there would be enough food to tide them over until next cycle of planting and harvest. Then two or three families would pack up their possessions, abandoning the small homestead where their ancestors had dwelled before them. They left with regret, perhaps, but comfortable with their decision, as they knew that the ancestors would have approved of it.
The great droughts of the American West had their origins in complex and still little-understood interactions between ocean and atmosphere in the Pacific. These same interactions, reflected in the cool cycle of the Pacific Decadal Oscillation and in the continual, unpredictable swings of El Niños and La Niñas, also brought havoc and food shortages to elaborate civilizations in Central America and the Andes.
CHAPTER 8
Lords of the Water Mountains
Again there comes a humiliation, destruction, and demolition. The manikins, woodcarvings were killed when the Heart of Sky devised a flood for them. A great flood was made: it came down on the heads of the manikins, woodcarvings.
—Popul Vuh, the Maya book of dawn of life1
HUNTING BANDS IN NORTH AMERICA’S Great Basin stayed close to shrinking water supplies and moved to higher ground. The Ancestral Pueblo abandoned Pueblo Bonito and the other great houses in Chaco Canyon, for centuries the sacred hub of their world, in the face of intense drought. Chumash Indian groups along the southern California coast fought each other over water and precious acorn crops devastated by persistent drought. All these peoples lived in semiarid landscapes, where flexibility and movement were automatic reactions to drought. Deep traditions of mutual obligation, of reciprocity, were a fundamental part of life in the American West, where the endlessly cycling pumps of deserts sucked in and pushed out people as rainfall came and went. Far to the south, in Central America, ancient Maya civilization was at its apogee when the droughts of the warm centuries arrived, bringing catastrophic disruption that killed thousands and depopulated much of the southern Maya lowlands.
Map of the Maya lowlands showing locations mentioned in the text.
JUST AS, in the 1970s, the decipherment of their script revolutionized our knowledge of the ancient Maya, so in the last few decades have deep-sea and lake borings provided insights into the climatic changes that rippled across their rainforest homeland a thousand years ago. The evidence for repeated, and often severe, drought mirrors that from western North America
The Cariaco basin, off Venezuela in the southeastern Caribbean, is the source of the most influential of all deep-sea cores, because it records climatic shifts resulting from the northward and southward movement of the Intertropical Convergence Zone (see sidebar in chapter 4). The ITCZ had a profound effect on rainfall in the Maya lowlands and across the ocean, on the Saharan Sahel. We can, in general terms, link climatic changes on either side of the Atlantic. As we shall see in chapter 11, there may even be connections across the Pacific to Asia. The Cariaco core is remarkable for its layers of fine sediment deposited annually by rivers flowing into the ocean.2 The deposits are unusual, for they are exceptionally well defined, with about 11.8 inches (30 centimeters) representing every millennium. The laminated sediments reflect fluctuations in river output caused by changing rainfall amounts. The changes result from seasonal shifts in the Intertropical Convergence Zone, dark laminae reflecting rainfall during the summer and fall rainy season, light-colored ones in the dry winter and spring, when the Convergence Zone is at its southernmost position and trade winds blow strongly along the Venezuelan coast. The bulk titanium content in the laminae records the amount of land-based sediment brought to the basin from surrounding watersheds. The higher the titanium content, the greater the rainfall.
Among sediments deposited over the past two thousand years, titanium concentrations were lowest between about five hundred and two hundred years ago, during the dry centuries of the Little Ice Age. Higher titanium concentrations arrived in the basin between A.D. 880 and 1100, the heart of the Medieval Warm Period. But the titanium levels were far from constant. There were pronounced minima in about A.D. 200, 300, and 750. Fortunately for climatologists, the Cariaco basin lies within the same climatic regimen as the Maya lowlands, where most rain falls during the summer, when the Intertropical Convergence Zone is at its north point over the Yucatán. If the Convergence Zone remains at its southernmost position for any length of time, drought hits both the Cariaco region and the Maya homeland.
Maya civilization flourished before about A.D. 150, when cities like El Mirador reached enormous size. El Mirador was abandoned rapidly during the early first millennium A.D., at a time when the Cariaco sea cores tell of drought in the area. But the Maya recovered, new cities arose, and new water management strategies came into use. Relatively wet times between A.D. 550 and 750 saw growing populations. Many Maya communities were soon operating at the limits of the carrying capacities of their lands. By this time, Maya settlements large and small were far more vulnerable to multiyear droughts, which would descend without warning but so infrequently that they lay outside the short generational memory of the day.
The Cariaco core documents a low-titanium interval centered on the ninth century, at the beginning of the Medieval Warm Period, a severe drought also found in a core bored in Lake Chichancanab in the Yu-catán itself.3 The two records chronicle multiyear droughts that began as early as A.D. 760, and reoccurred at about fifty-year intervals: 760, 820, 860, and 910. The first drought was a slight long-term drying trend, followed by a severe drought of about three years beginning in 810, and another drought beginning in about 910 and lasting for about six years. It was during this period that Maya civilization in the southern and central Yucatán lowlands collapsed.
The Lake Chichancanab core not only mirrors that from Cariaco, though it can be dated somewhat less accurately (plus or minus twenty years), but also documents drought conditions lasting until A.D. 1075. The climate record is now unequivocal. Drought cycles during the early Medieval Warm Period settled over the Maya lowlands at about fifty-year intervals, at the same time as profound aridity affected western North America.
THE MAYA WERE obsessed with water, and with good reason, for they lived in an environment of uncertain rainfall. They believed that civilization began in the dark primordial waters of Xibalba, the Otherworld. The waters were calm and dark, the world nothing but water. “There is not yet one person, one animal, bird, fish, crab, tree, rock, hollow canyon, meadow, forest. Only the sky alone is there; the face of the earth is not clear. Only the sea alone is pooled all under the sky; there is nothing whatever gathered together. It is all at rest.” Xibalba was a calm, dark pool. But there were signs of movement
in the water, “murmurs, ripples, in the dark, in the night.” The creators were in the waters, “a glittering light. They are there, they are enclosed in quetzal feathers, in blue-green.”4 Here the gods created humanity. Once they had done so, they caused water to well out of the entrances to the nether regions, the most sacred places in the Maya landscape, to nourish crops and nurture human life. Water defined this most flamboyant of native American civilizations in subtle ways, and became an instrument of political power and social control. The cycle of Maya life ended when great lords descended in death to Xibalba’s inky waters. And when the rains failed and drought descended on the Maya world, the foundations of civilization quivered.
Like the ancient Egyptians, the Maya were village farmers for many centuries before they transformed their homeland into a landscape of great cities ruled by powerful lords.5 There the resemblance ends. No annual inundation or fertile river floodplain provided a safety net for Maya civilization. Nor did any great rivers link cities, towns, and villages into a large, unified state like that of the pharaohs. The Maya farmed the Petén-Yucatán peninsula, which juts into the Gulf of Mexico; it is a vast limestone shelf lifted from the depths of the ocean over an immense length of time. They lived in a densely forested world where huge mahogany trees towered as much as 150 feet (45 meters) above the ground, where sapodilla and breadnut abounded. The forest gave way to patches of open savanna covered with coarse grass and stunted trees. Hot, humid, and generally poorly drained, the Maya lowlands were a fragile, water-stressed environment even at the best of times. The porous limestone bedrock absorbed water to the point where fluctuations in the water table were unpredictable. It’s hard to imagine a less likely place for a great civilization.
Fly over the homeland of Classic Maya civilization (A.D. 250–900) in the lower Yucatán and you pass over a featureless green carpet. But the seeming uniformity is an illusion. The dense tree cover masks an astonishing diversity of local habitats, all of which presented special challenges to ancient Maya farmers. Between 53 and 78 inches (1,350 and 2,000 millimeters) of rain fell each year, but precipitation was less abundant and predictable than one might expect. Most rain arrived between May and October, after a dry season that lasted between four and six months. Lakes, springs, and perennial streams were priceless rarities. Even small-scale village farming required creative ways of collecting, storing, and managing water for the long dry months.
TO UNDERSTAND WHY, we must journey back to the beginnings of the Maya. In about 1000 B.C., only the coastal plain and a few small, perennial drainages could support permanent farming communities for the long term. Many of these communities were also involved in fishing. As local populations increased, so small groups moved inland along streams and the swamps that bordered them. Within six centuries, a patchwork of tiny villages had become a rapidly growing civilization.
By the third century B.C., thousands of people lived in scattered communities across the lowlands. They were adept, patient farmers, who developed many ways of managing water and modifying the environment for maximum productivity. Generations of trial and error, of hunger and plenty, led people to settle at strategic locations—for example, they could live near the base of shallow natural depressions that received surface runoff during the rainy season.6 There they constructed reservoirs to store rainwater, close to places where the first great ceremonial centers rose with remarkable speed. By any standards, these were imposing structures. For instance, between 150 B.C. and A.D. 50, a mere two centuries, El Mirador in Guatemala’s Petén grew to cover 6 square miles (16 square kilometers), dominated by the Danta Pyramid, built on a natural hill more than 230 feet (70 meters) high.7 The city lay amidst an undulating landscape, where water collected in a large, basically natural watershed during the rainy season. Causeways traversed low-lying swamps or shallow lakes near the central area. El Mirador thrived thanks to a simple form of water management, by which large natural depressions, extended into reservoirs, served as water storage facilities. The same reservoir system was also an integral part of an extensive agricultural landscape.
Some of these systems reached considerable size. The people of Edzná in Campeche, occupied between 400 B.C. and A.D. 150, excavated huge canal basins and removed nearly 62 million cubic feet (1.75 million cubic meters) of fill to build them—more than the volume of Teotihuacán’s vast Pyramid of the Sun far away in the Mexican highlands.8 Then, suddenly, during the first and second centuries, El Mirador, Edzná, and the other growing centers collapsed. Their pyramids and temples were abandoned to the forest; the people dispersed into small villages scattered across the landscape. Many experts believe this was because of a severe drought that rendered their reservoirs and simple water systems virtually useless.
After A.D. 250, the start of the Classic period of Maya civilization, water management strategies changed. For the first time, Maya lords built palaces, pyramids, and temples on elevated ridges and hillocks. They moved their centers away from natural water sources and chose to build large reservoirs close to their ceremonial precincts. The largest cities, among them Calakmul, Copán, and Tikal, developed elaborate water management systems, built as part of the process of erecting the plazas and pyramids that were symbolic replicas of the Maya world. The pyramids became “water mountains.” Thousands of villagers labored over the great centers. The first order of business was to quarry stone, to create the artificial depressions that would become reservoirs and tanks. Without a viable water system, the builders had no drinking supplies for work gangs or for mixing the limestone mortar used for floors and walls. The labor investment was enormous, but no urban center could survive without far larger-scale water supplies than those required by a small farming village.
Every Maya lord built his largest reservoirs and tanks close to his most imposing civic architecture. Here he appeared before the assembled populace in elaborate public ceremonies. Here dancers would perform in open plazas dwarfed by high temples. Here chants would resonate from pyramid stairways, torches flickering and flaring in the night breeze as incense wafted among the crowd. The ruler himself would emerge from a dark opening in the temple, the symbolic entryway to Xibalba, and appear before the people in a state of trance induced by hallucinogenic drugs. He performed ritual bloodletting on himself, then vanished abruptly, embarking on a journey into the supernatural world. The great rituals revolved around the complex relationships between the living, the deities, and the ancestors, between the rulers and the ruled. The same ceremonies recognized the central place of water in Maya life—and in the complex equations of political power. From earliest times, Maya society had thrived on kin ties that linked community to community with vital ties of reciprocity—the obligation to provide food, assistance, or labor to kin in times of need. As Maya civilization emerged from its village roots and new leaders came into prominence, ancient kin ties still provided at least a theoretical link between lords and commoners. But the nature of the ties between them changed from simple reciprocity to a more elaborate social contract. Maya rulers proclaimed themselves divine lords, with exceptional supernatural powers. They became like shamans, capable of passing freely into the supernatural world, where they served as intermediaries between the living Maya, their ancestors, and the forces of the spiritual world. The lords provided supernatural protection, fostering rain and good crops. In exchange, the people paid tribute and taxes in food and labor. They worked when called upon for the nobility, for the public good, in an unwritten alliance that justified social inequality. As long as there was ample rainfall, the tacit contract survived. But once the fallibility of the lords became apparent, social disorder ensued.
TIKAL, THE GREATEST of the Maya cities, was dominated by the most imposing of all water mountains, founded during the first century A.D.9 Thirty-one rulers, the earliest dating to A.D. 292, the latest to A.D. 869, left nearly 600 years of recorded history here. By a combination of judicious political marriages and warfare, Tikal’s lords extended their sway over neighboring center
s, ruling at one point over between 200,000 and 300,000 people. No one knows how many people lived in the center, surrounded as it was by a hinterland of villages and larger communities. But we do know that the city depended entirely on seasonal rainfall for its water supplies.
The amount of water collected at Tikal was truly astounding. Six catchment areas surrounded the major hillock where the city lay. One central-precinct catchment alone covered 156 acres (63 hectares) and could collect more than 31.7 million cubic feet (900,000 cubic meters) of water in a year when 59 inches (1500 millimeters) of rain fell—an amount typical of a nondrought period. Slightly canted pavements and subtly diverted weirs directed rainfall into the central-precinct reservoirs, which were sealed with stones and imported clay. The combined reservoirs could hold between 3.5 million and 7 million cubic feet (100,000 and 200,000 cubic meters) of water, enough to allow controlled release of water during the dry season, using carefully placed sluice gates under the city’s causeways. Small domestic tanks for the houses immediately below the summit were probably recharged from the central system. Four large reservoirs lay near the foot of the central hillock and around the swampy margins of Tikal, designed to recapture gray and reused water from upslope residential areas. The 1.76 to 6.1 million cubic feet (50,000 to 175,000 cubic meters) of runoff served to irrigate about 210 acres (85 hectares) of swamp-margin plots around the city.10 With water available year-round, local farmers could potentially raise two crops a year.