Urbanization—the origin, growth, and spread of cities—has been of great importance to the social and economic history of humanity over the past 6,000 years or more. Urbanization is also of major importance in considering humanity's relation to the natural world— both in terms of the factors that are actively destroying the world's ecosystems and species in the current "biodiversity crisis" (see Sixth Extinction), as well as the positive aspects of organizing and implementing solutions to the world's environmental problems.

Damascus, in Syria, is generally regarded as the world's oldest city; archaeologists are confident that there were people living at the present site of Damascus as long ago as 6000 B.C.; some think that the city might be as old as 10,000 years—reaching back as far as the very beginnings of agriculture. And the link between cities and agriculture is crucial to understanding how and why people have come to live in the densely localized concentrations that we call cities. Prior to the invention of agriculture, some 10,000 years ago, there were no cities—because there could be no cities.

Prior to the invention of agriculture, all humanity existed as hunter-gatherers: people would hunt the animals (game and fish) and gather the plants (fruits, nuts, tubers, leaves, grains, and so forth) that occurred locally. Bands of hunter-gatherers rarely exceeded seventy people and were often smaller; their numbers were limited by the "carrying capacity" of the environment—that is, the amount of food available to sustain a population of humans. Eventually, all the readily hunted game and easily collected plants would be exhausted, and the band would have to move on. Sometimes they would follow migrating herds of game, but all hunter-gatherers were either fully, or at least partially, nomadic. There simply was not enough food available year-round, or for many years running, to allow people to have a completely settled existence.

Agriculture changed all that. When agriculture was invented (independently, in several places, but perhaps earliest in the Middle East around 10,000 years ago), people learned to transform the grasslands and forests of their native regions into cleared fields, in which they planted one or more crop species (from seeds they had formerly collected growing wild). Although history is full of examples of crop failure and episodes of starvation—from ancient Egypt right up to the present day—it is nevertheless true that, for the most part,

many more people can be sustained by agricultural productivity than by hunting for meat and foraging for edible plants. The simple proof of that statement is that there were only some 5 to 6 million people on earth at the dawn of agriculture, but now, a scant 10,000 years since human sustenance switched to agriculture and the animal husbandry that goes along with farming, our population has exceeded 6 billion.

But farming requires open land—just the opposite of cities. Flying over the central regions of the United States in the modern era confirms that cities are scattered, often quite far from one another, almost as islands in a sea of farmland. So agriculture doesn't cause cities to grow. But agriculture does require that people remain in one place in order to tend the fields and animals—almost always a year-round proposition. It can supply the food resources that, along with adequate water supplies, are the bare essentials for large concentrations of human beings to develop. And, crucially, agriculture eliminates the necessity for everyone living in a localized region to be engaged in food procurement (in hunter-gatherer societies, women usually gather the edible plants, while men usually do the hunting; all able-bodied adults take part in hunting and gathering food). With the division of labor made possible by agriculture, people began to specialize: for example, some wove, or made pots, or shoes, or bread—which could then be bartered for meats and grains.

As population numbers began to grow in the early days of agriculture, local towns developed. Early agriculture occurred predominantly along fertile river valleys, such as the Indus (India), Tigris and Euphrates (the "Fertile Crescent" of Mesopotamia), and the Nile in Egypt. City-states began to emerge along these waterways as political control of water resources (for example, for irrigation and navigation) began to be important. Towns grew into cities, often with walls for protection from raids from neighboring cities and nations.

Although cities are often full of parks and gardens, most cities—from ancient Egypt up to the present—are dense concentrations of roads and buildings. The streets of modern cities are paved in concrete and macadam, with large stone, steel, glass, and concrete buildings lining their sides. From this perspective there can seem to be no more thoroughly environmentally destructive human activity than the construction of a city. And with their need to feed and supply safe water to ever-larger numbers (some cities have pop ulations as high as 15 to 20 million—all of which produce large amounts of waste each day), cities must reach out far afield for their supplies. Around 1900, Brooklyn (itself then considered the third largest city in the United States) was the principal supplier of fruits and vegetables to New York City (then only Manhattan). Nowadays, New York gets its fruits and vegetables, not only from neighboring communities (no longer Brooklyn, but Long Island and New Jersey), and also from Florida and California. But that's not all: countries as far from New York as Israel and Chile send produce to New York every day. And the very act of consuming what is produced elsewhere around the globe contributes to the drain on the world's environment.

If, however, cities put a tremendous strain on the natural world, contributing greatly to the degradation of the world's ecosystems and the loss of species both near and far, they also present a very positive hope for the future. For it is cities that contain the greatest concentration of knowledge—in universities, for example, as well as in research institutes and museums (see Museums and Biodiversity). Political institutions, as well, are focused in cities (for example, the UN headquarters are in New York), and the solutions to the world's problems always involve political institutions. The news media are concentrated in cities—important sources of information that underlie discussion and decision-making on environmental and other problems. And wealth: cities are sometimes heavily populated by desperately poor people, but most of any nation's wealth is controlled by corporations and individuals that are located for the most part in cities. And if wealth and international trade contribute to the environmental difficulties the world is facing, they also are necessary ingredients of a rational approach to sustainable development that we shall have to achieve to put the utilization of global resources on a sounder, more environmentally friendly footing.

—Niles Eldredge

See also: Agriculture, Origin of; Economics; Ecosystems; Museums and Biodiversity; Sixth Extinction; Species


Cohen, Joel E. 1995. How Many People Can the Earth Support? New York: W. W. Norton; Eldredge, Niles. 1997. Dominion. Berkeley: University of California Press; Eldredge, Niles. 1998. Life in the Balance: Humanity and the Biodiversity Crisis. Princeton: Princeton University Press; Toynbee, Arnold. 1976. Mankind and Mother Earth. New York: Oxford University Press.

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