Did you know? China is planting a belt of trees to protect land from the expanding Gobi Desert. This Great Green Wall is projected to extend some 4,480 kilometers (2,800 miles), stretching from outer Beijing through Inner Mongolia (Nei Monggol). Unfortunately, recent pressures to expand food production appear to have slowed this tree planting initiative. For more information view the text and data in Chapter 8 of Plan B 4.0: Mobilizing to Save Civilization.
Chapter 1. the Economy and the Earth: Lessons from the Past
In The Collapse of Complex Civilizations, Joseph Tainter describes the decline of early civilizations and speculates about the causes. Was it because of the degradation of their environment, climate change, civil conflict, foreign invaders? Or, he asks, "is there some mysterious internal dynamic to the rise and fall of civilizations?"33
As he ponders the contrast between civilizations that once flourished and the desolation of the sites they occupied, he quotes archeologist Robert McC. Adams, who described the site of the ancient Sumerian civilization located on the central floodplain of the Euphrates River, an empty, desolate area now outside the frontiers of cultivation. Adams described how the "tangled dunes, long disused canal levees, and the rubble-strewn mounds of former settlement contribute only low, featureless relief. Vegetation is sparse, and in many areas it is almost wholly absent..Yet at one time, here lay the core, the heartland, the oldest urban, literate civilization in the world."34
The early Sumerian civilization of the fourth millennium BC was remarkable, advancing far beyond any that had existed before. Its irrigation system, based on sophisticated engineering concepts, created a highly productive agriculture, one that enabled farmers to produce a surplus of food that supported the formation of the first cities. Managing the irrigation system required a complex social organization, one that may have been more sophisticated than any that had gone before. The Sumerians had the first cities and the first written language, the cuneiform script. They were probably as excited about it as we are today about the Internet.35
It was an extraordinary civilization, but there was an environmental flaw in the design of the irrigation system, one that would eventually undermine its agricultural economy. Water from behind dams was diverted onto the land, raising crop yields. Some of the water was used by the crops, some evaporated into the atmosphere, and some percolated downward. Over time, this percolation slowly raised the water table until eventually it approached the surface of the land. When it reached a few feet from the surface it began to restrict the growth of deep-rooted crops. Somewhat later, as the water climbed to within inches of the surface, it began to evaporate into the atmosphere. As this happened, the salt in the water was left behind. Over time, the accumulation of salt reduced the productivity of the land. The environmental flaw was that there was no provision for draining the water that percolated downward.36
The initial response of the Sumerians to declining wheat yields was to shift to barley, a more salt-tolerant plant. But eventually the yields of barley also declined. The resultant shrinkage of the food supply undermined the economic foundation of this great civilization.37 The New World counterpart to Sumer is the Mayan civilization that developed in the lowlands of what is now Guatemala. It flourished from AD 250 until its collapse around AD 900. Like the Sumerians, the Mayans had developed a sophisticated, highly productive agriculture, one that relied on raised plots of earth surrounded by canals that supplied water.38
As with Sumer, the Mayan demise was apparently linked to a failing food supply. For this New World civilization, it was deforestation and soil erosion that undermined agriculture. Food scarcity may then have triggered civil conflict among the various Mayan cities as they competed for food.39
During the later centuries of the Mayan civilization, a new society was evolving on Easter Island, some 166 square kilometers of land in the South Pacific roughly 3,200 kilometers west of South America and 2,200 kilometers from Pitcairn Island, the nearest habitation. Settled around AD 400, this civilization flourished on a volcanic island with rich soils and lush vegetation, including trees that grew 25 meters tall with trunks 2 meters in diameter. Archeological records indicate that the islanders ate mainly seafood, principally dolphins-a mammal that could only be caught by harpoon from large sea-going canoes since it was not locally available in large numbers.40
The Easter Island society flourished for several centuries, reaching an estimated population of 20,000. As its human numbers gradually increased, tree cutting exceeded the sustainable yield of forests. Eventually the large trees needed to build the sturdy, ocean-going canoes disappeared, depriving islanders of access to the dolphins, thus dramatically shrinking the island's seafood supply. The archeological record shows that at some point human bones became intermingled with the dolphin bones, suggesting a desperate society that had resorted to cannibalism. Today the island is occupied by some 2,000 people.41
These are just three of the early civilizations that declined apparently because at some point they moved onto an economic path that was environmentally unsustainable. We, too, are on such a path. Any one of several trends of environmental degradation could undermine civilization as we know it. Just as the irrigation system that defined the early Sumerian economy had a flaw, so too does the fossil fuel energy system that defines our modern economy. It is raising CO2 levels in the atmosphere and thus altering the earth's climate.
Whether it was from the salting of the land in Sumer, the soil erosion of the Mayans, or the loss of the distant-water fishing capacity of the Easter Islanders, collapse of the early civilizations appears to have been associated with a decline in food supply. Today the addition of 80 million people a year to world population at a time when water tables are falling suggests that food supplies again may be the vulnerable link between the environment and the economy.42
The Sumerians did not know that the New World even existed, much less that it would one day support flourishing civilizations, such as the Mayans. The Mayans had no idea that Easter Island existed. Each of these civilizations collapsed in isolation, with no effect on the others. But today, in an integrated global economy, a collapse in one country or region will affect all of us. Even a currency devaluation in a developing country, such as Indonesia, can send shock waves through Wall Street half a world away.
One unanswerable question about these earlier civilizations was whether they knew what was causing their decline. Did the Sumerians understand that rising salt content in the soil was reducing their wheat yields? If they knew, were they simply unable to muster the political support needed to lower water tables, just as we today are struggling unsuccessfully to lower carbon emissions?
33. Joseph Tainter, The Collapse of Complex Civilizations (Cambridge: Cambridge University Press, 1988), p. 1.
35. Postel, op. cit note 3, pp. 13-21.
38. "Maya," Encyclopaedia Britannica, online encyclopedia, viewed 7 August 2000.
40. Jared Diamond, "Easter's End," Discover, August 1995, pp. 63-69.
42. Population addition from United Nations, op. cit. note 25.
Copyright © 2001 Earth Policy Institute