Despite Earth’s superabundance of total water, nature endowed to mankind a surprisingly minuscule amount of accessible fresh liquid water that is indispensable to planetary life and human civilization. Only 2.5 percent of Earth’s water is fresh. But two-thirds of that is locked away from man’s use in ice caps and glaciers. All but a few drops of the remaining one-third is also inaccessible, or prohibitively expensive to extract, because it lies in rocky, underground aquifers—in effect, isolated underground lakes—many a half mile or more deep inside Earth’s bowels. Such aquifers hold up to an estimated 100 times more liquid freshwater than exists on the surface. In all, less than three-tenths of 1 percent of total freshwater is in liquid form on the surface. The remainder is in permafrost and soil moisture, in the body of plants and animals, and in the air as vapor.
One of the most striking facts about the world’s freshwater is that the most widely accessed source by societies throughout history—rivers and streams—hold just six-thousandths of 1 percent of the total. Some societies have been built around the edges of lakes, which cumulatively hold some 40 times more than rivers. Yet lake water has been a far less useful direct resource to large civilizations because its accessible perimeters are so much smaller than riversides. Moreover, many are located in inhospitable frozen regions or mountain highlands, and three-fourths are concentrated in just three lake systems: Siberia’s remote, deep Lake Baikal, North America’s Great Lakes, and East Africa’s mountainous rift lakes, chiefly Tanganyika and Nyasa. Throughout history, societies have also widely accessed shallow, slowly flowing groundwater, which is the underground counterpart of surface rivers and lakes.
The minuscule, less than 1 percent total stock of accessible freshwater, however, is not the actual amount available to mankind since rivers, lakes, and shallow groundwater are constantly being replenished through Earth’s desalinating water cycle of evaporation and precipitation—at any given moment in time, four-hundredths of 1 percent of Earth’s water is in the process of being recycled through the atmosphere. Most of the evaporated water comes from the oceans and falls back into them as rain or snow. But a small, net positive amount of desalted, cleansed ocean water precipitates over land to renew its freshwater ecosystems before running off to the sea. Of that amount, civilizations since the dawn of history have had practical access only to a fraction, since two-thirds was rapidly lost in floods, evaporation, and directly in soil absorption, while a lot of the rest ran off in regions like the tropics or frozen lands too remote from large populations to be captured and utilized. Indeed, the dispersion of available freshwater on Earth is strikingly uneven. Globally, one-third of all streamflow occurs in Brazil, Russia, Canada, and the United States, with a combined one-tenth of the world’s population. Semiarid lands with one-third of world population, by contrast, get just 8 percent of renewable supply. Due to the extreme difficulty of managing such a heavy liquid—weighing 8.34 pounds per gallon, or over 20 percent more than oil—societies’ fates throughout history have rested heavily on their capacity to increase supply and command over their local water resources.
Some societies developed in landscapes that offered relatively abundant, easily accessible, water resources with reliable availability and moderate variations; others have been hindered by more water-fragile and arduous habitats marked by dearth or excess and, worst of all, frequent, unpredictable shocks like extreme droughts and floods that overwhelmed otherwise sound hydraulic planning. Each unique environment imposed opportunities and constraints that helped shape that society’s organizational patterns and history.
Adaptation is a constant necessity because water conditions are in flux. As historians Ariel and Will Durant have written, “Every day the sea encroaches somewhere upon the land, or the land upon the sea; cities disappear under the water…rivers swell and flood, or dry up, or change their course; valleys become deserts, and isthmuses become straits…Let rain become too rare and civilization disappears under sand… let it fall too furiously, and civilization will be choked with jungle.” Natural secular climate change alters conditions slowly, but dramatically, over time. As recently as 5,000 years ago the Sahara Desert was verdant grassland with hippopotamuses, elephants, and cattle herders, whose water has since evaporated and seeped away into deep, fossil aquifers, while today’s desiccating, windblown northern plain of the Yellow River was a watery swampland at the time it was a cradle of ancient Chinese civilization. Almost everywhere civilization has taken root, man-made deforestation, water diversion, and irrigation schemes have produced greater desiccation, soil erosion, and the ruination of Earth’s natural fertility to sustain plant life.
How societies respond to the challenges presented by the changing hydraulic conditions of its environment using the technological and organizational tools of its times is, quite simply, one of the central motive forces of history. Repeatedly, leading civilizations have been those that transcended their natural water obstacles to unlock and leverage the often hidden benefits of the planet’s most indispensable resource.
CHAPTER TWO
Water and the Start of Civilization
In A Study of History, British historian Arnold Toynbee influentially posited that the history of civilizations was centrally driven by a dynamic process of responses to environmental challenges. Difficult challenges provoked exceptional, civilizing responses in ascendant societies, while inadequate responses contributed to stagnancy, subordination, and collapse in declining ones. Prominent among the environmental challenges was water.
Throughout history, wherever water resources have been increased and made most manageable, navigable, and potable, societies have generally been robust and long enduring. Those that succeeded in significantly increasing their command and supply regularly were among the few that broke out of history’s normative condition of changelessness and bare subsistence to enjoy spurts of prosperity, political vigor, and even momentary preeminence. Often major water innovations leveraged the economic, population, and territorial expansions that animated world history. Those unable to overcome the challenge of being farthest removed from access to the best water resources, by contrast, were invariably among history’s poor.
Water’s leading role in civilization was visible in the landscape of natural and man-improved waterways that ever have been history’s directional arrows of exploration, trade, colonial settlement, military conquests, agricultural expansion, and industrial development. Wherever navigable waterways converged or where key river crossings or favorable harbors were established, influential urban centers arose at the center of civilizations. In every age, whoever gained control of the world’s main sea-lanes or the watersheds of great rivers commanded the gateways of imperial power. If the advance of civilization could be charted on an electronic, time-sequenced map of the globe, it would show early city-states unifying up river valleys, along seacoasts, then spreading across nearby seas, and finally extending westward to link all the world’s oceans and waterways in an ever-denser and faster-traveled web that has evolved into today’s fitfully integrated global economy and world civilization.
It was also a common pattern of history that expansions driven by intensified use of water and other vital resources were followed by population increases that in turn so increased consumption that they ultimately depleted the further intensification capacity of the society’s existing resource base and technologies. Such resource depletions thus presented each society with a moving target of new challenges requiring perpetually new innovative responses to sustain growth. This population-resource equation—the ever-shifting balance between each society’s population size and the resources and know-how within its means to produce enough goods to sustain it—and its activating cycle of intensification and resource depletion, too, was one of the central dynamics of human and water history. History was littered with societies that declined simply because they could not overcome the deleterious local-resource depletions and population expansions accompanying their own initial success.
Water tied man to Earth with a special bond. Fetuses gestated in water. Man and environment mutually exchanged water through the natural biological cycles of perspiration, exhalation and evacuation, and replenishment by drinking. A healthy, active person needed to consume at least two to three quarts of freshwater daily to stay alive—there was no substitute. Thirst came with only a 1 percent water deficiency; a 5 percent shortfall produced a fever; a 10 percent dearth caused immobility; death struck after about a week with a 12 to 15 percent water loss.
The special affinity between water and man was reflected in water’s primary role in creation stories in diverse cultures throughout the world. “Almost every mythology sees the origins of life coming out of water,” observed mythologist Joseph Campbell. “And, curiously, that’s true. It’s amusing that the origin of life out of water is in myths and then again, finally, in science, we find the same thing.” Water was one of the Greeks’ four primary terrestrial elements and one of five in ancient China and Mesopotamia. Water still plays a central role in common religious rituals of purification from Hinduism and Shinto to Islam, Christianity, and Judaism. Whether it was the rain dance of a tribal shaman, the ritual opening of an irrigation canal by an ancient king, or the dedication of a giant hydroelectric dam by a twentieth-century president, provision and control of sufficient water has conferred political legitimacy in all forms of human society.
Yet water’s unique natural characteristics always simultaneously presented a double-edged challenge to civilized man: it was at once the necessary resource of survival that when brought under control yielded immeasurable benefits to society, but it also imposed one of the most formidable natural obstacles and limitations to growth. Water sustained life, but also, through the devastating shocks of drought, flood, and mudslide, could obliterate it on a terrifying scale, as witnessed in the quarter of a million deaths in the Indian Ocean tsunami of late 2004 and the traumatic 2005 inundation of New Orleans. While man needed water to live, drinking contaminated water and exposure to stagnant water infested with disease-carrying organisms was by far the leading cause of debilitating illness, infant mortality, and short life spans for all of history. Rivers, seas, and the waterless oceans of the deserts could be protective or constraining, in turn a separating defensive buffer between societies, or a bridge between peoples to open communication and trade, or a highway of invasion and conquest. Irrigation watered cropland, but also raised fertility-killing salts to the soil’s surface. The secret of water’s extraordinary potency to transform history was that whenever a society, in its constant struggle to wrench a surplus from nature, was able to innovate to make its water resources more manageable, abundant, potable, or navigable, it not only merely liberated itself from a major water-bound obstacle and constraint, but also unlocked and harnessed more of water’s inherent, often hidden catalytic potential for growth.
A radical transformation in man’s relationship to water played a pivotal role in the great transition to settled agriculture at the start of history. After eons as hunter-gatherers following their alimentary mainstay of herds of giant herbivores such as steppe bison, giant elk, and woolly mammoth from seasonal water hole to water hole, and gathering wild, edible plants along the way, some human tribes about 10,000 years ago began to adopt a settled economic life predicated upon the artificial transformation of nature through farming. As a hunter-gatherer, primitive man used water as he found it. As a settled farmer, managing water resources became essential to survival and growth.
Environmental change in climate and water conditions offered the most likely explanation of the mystery why hunter-gatherers suddenly traded their relatively undemanding and healthy lifestyle for the more-labor-intensive, less-healthy challenges of farming life. As the ice age glaciers retreated northward due to increased global warming and moisture at the start of the present warm period, tundra mosses and grasses also retreated and were gradually replaced by thick temperate forests. This forced the large herds ever northward after their food supply. An abrupt, 1,300-year-long mini ice age around 12,900 years ago may have accelerated the herds’ disappearance. Some groups gave up following the herds to hunt smaller animals, fish, and gather the wild cereals and other edible plants that flourished on open landscapes. Experiments with settled farming and animal domestication ensued. Gradually, domesticated seed agriculture based on wild barley and emmer wheat grasses emerged in the Middle East’s Fertile Crescent, which had transformed from prairie to semiarid landscapes as the climate changed. Farmers began to work the amply rain-fed, well-drained, and easier-to-work soils of wooded river valley hillsides with simple stone and wooden axes, hoes, and sickles. Slashing the bark killed enough trees for sunlight to nourish seeds planted in the loose leaf mold around the trunks. Scattered ash from burning the dead trees after two or three plantings temporarily revitalized the soil’s depleted fertility for another few seasons. Finally, weed invasion forced such “slash-and-burn” method farmers to abandon the land and move on to clear new plots. Early walled, irrigated farming and trading settlements ultimately arose in a few favored locations. Jericho, possibly the world’s oldest true city from about 7000 BC, with about 3,000 inhabitants, internal cisterns, grain storerooms, and a tower within its 10 acres, was situated at the lower slope of Mount Carmel near an ample “sweet,” or freshwater, spring—in contrast to “bitter” water with traces of salt—known in the Bible as Elisha’s Spring that irrigated the small, fertile, once-forested Jordan River valley and was later to lure the biblical Joshua and his Hebrew followers after the exodus from Egypt. Jericho’s location also gave it access to the precious salt and trade routes of the Dead Sea. Salt had become vital to maintaining body fluid once the human diet had shifted to cereals.
Slash-and-burn farming on hillsides had one major drawback. It was always extremely vulnerable to erratic rainfall. The response to this environmental challenge produced one of history’s most momentous innovations—the rise of large-scale, irrigated agriculture, and with it the birth of civilization. The earliest irrigated farming civilizations all developed along the semiarid plains of large, flooding, soil-bearing rivers where precipitation was too scant for rain-fed agriculture. In Mesopotamia, where civilization arose first, some hillside farmers moved down into the stoneless,
muddy floodplains and swamps of the lower Tigris-Euphrates river valley in Sumeria near the mouth of the Persian Gulf. It would seem to be counterintuitive for farmers to relocate into a forbidding, miasmic habitat marked by scant rainfall and infestations of deadly waterborne diseases, and prone to violent floods and droughts. Yet the rivers possessed two prized resources that trumped all drawbacks—an ample, reliable, year-round supply of freshwater and a self-renewing source of fertile silt that spread across the cropland with the floods. If productively managed by the arduous building and maintenance of irrigation waterworks, the water supply and silt could produce bountiful yields many times greater than were possible on the rain-dependent hillsides. By specializing in the mass production on cultivated fields of one or two staples like wheat, barley, or millet, farm communities that mastered the techniques of irrigation ultimately produced grain surpluses that were stored as reserves for bad seasons when the floods were excessive or inadequate. These food surpluses in turn yielded rising populations, big cities, and all the early expressions of civilization—arts, writing, taxation, and the first large states—that were the precursors of modern society. The development of reed and wooden rafts, powered by oar and sail, also turned the rivers into high roads for trade, communication, and political integration. As political power concentrated and production of field seed grains expanded with better organization, these early, river-based irrigation civilizations became cradles of history’s first great empires.
Steven Solomon Page 2
