Download Environmental Disasters in the Cradles of Civilization

Environmental Disasters in the Cradles of Civilization
Agriculture was probably the most important invention in human history. It
enabled the rise of world civilizations. But many ancient societies repeatedly chose
short-sighted food production practices that spoiled their environments and
undermined their civilizations.
The Sumerian Puzzle
The Tigris and Euphrates rivers begin in the mountains of Turkey and flow south
for more than a thousand miles through modern-day Iraq to the Persian Gulf. Known in
ancient times as Mesopotamia, the lands between these two rivers lacked adequate
rainfall for agriculture. But people could always use water from the rivers for their crops.
By 5000 B.C., many small farming villages flourished near the banks of the two
great rivers. The farmers dug simple ditches to irrigate their fields of wheat, barley, and
vegetables. The resulting increase in the food supply led to a population explosion.
Several hundred years later, independent city-states like Ur arose. They had
populations ranging from 10,000 to 50,000 people. By 3000 B.C., the city-states of
southern Mesopotamia had formed the world's first civilization, called Sumer.
The Sumerians developed a complex class system that included priests, rulers, a
government bureaucracy, craft workers, merchants, laborers, soldiers, and peasants who
worked the fields. The rulers organized major building projects in the cities. They
constructed canals for a large irrigation system that opened more land for growing food
crops. The Sumerians also developed the world's first writing system.
In the early 20th century, archaeologists in Mesopotamia puzzled over the barren desert
that had once been a rich and powerful civilization. "What happened to Sumer?" they
asked themselves.
Over the centuries, silt carried by the Tigris and Euphrates built up the stream
beds. Eventually, the surrounding farmlands were below the level of the rivers. The
Sumerians constructed levees to contain the rivers, which worked except during major
floods.
The irrigated water went to the fields, where it often collected on the surface. The
hot Mesopotamian sun evaporated the standing water and left behind layers of salt. The
soil also became waterlogged in places. This caused the water table to rise, bringing more
salt to the surface. One clay tablet with Sumerian writing recorded that "the earth turned
white."
The only solution to this salt problem, called salinization, was for the Sumerians
to leave the land unwatered and fallow for several seasons to allow the water table to fall.
The scarce rains would then slowly draw the salt down below the soil cultivation zone.
The Sumerian farmers knew that leaving the land alone for a while was the right thing to
do. But the rulers of Sumer had based their wealth and power on the skills and labor of an
ever-growing population. Therefore, they ordered the farmers to continue irrigating and
planting the damaged land to produce more food.
Wheat is less tolerant of salt than barley. Based on clay tablet records, barley
gradually replaced wheat in the Sumerian diet. Soon, the yields of barley and the other
crops decreased steadily. The Sumerian people began to suffer from hunger, which led to
malnutrition and disease.
The shortsighted demands of the Sumerian rulers led to the collapse of their
civilization. The rulers could no longer feed and pay for large armies. Peasant revolts and
warfare among the Sumerian city-states erupted over control of remaining fertile
farmlands. Finally, in 2370 B.C., the Akkadian Empire from the north conquered a
weakened Sumer.
By 1800 B.C., agriculture in southern Mesopotamia had almost disappeared, leaving
an impoverished people who lived on a desolate and poisoned land. The world's first
civilization had created a monumental environmental disaster.
Another Version of the Same Story
fhttp://www.crf-usa.org/bria/bria18_4a.htm
Mesopotamia was known as the land between two rivers, the Tigris to the north and the
Euphrates to the south. Rains were seasonal in this area, which meant that the land
flooded in the winter and spring and water was scarce at other times. Farming in the
region depended on irrigation from the Tigris and Euphrates Rivers. Many resources in
Mesopotamia were scarce or absent, which stimulated trade in the region in ancient
times. Supported by lucrative trade with its neighbors, Mesopotamia grew to become a
powerful empire.
Mashkan-shapir was a typical Mesopotamian city, located about 20 miles from
the Tigris River and connected to the river by a network of canals. Despite a flourishing
civilization, Mashkan-shapir was abandoned within only 20 years of its settlement. What
could have caused this rapid demise?
Poisoned fields: A contributor to collapse
Along with factors such as war and changes in the environment, scientists now
believe irrigation techniques played an important role in Mashkan-shapir's collapse. The
same process that allowed farming in this region also eventually made it impossible to
farm. Irrigation has a Catch-22: if irrigation water is allowed to sit on the fields and
evaporate, it leaves behind mineral salts; if attempts are made to drain off irrigation water
and it flows through the soil too quickly, erosion becomes a problem. Scientists believe
that Mashkan-shapir's collapse was caused in part by destruction of the fields by mineral
salts. When mineral salts concentrate in the upper levels of the soil, it becomes poisonous
for plants.
In Mesopotamia, irrigation was essential for crop production. The rivers were higher
than the surrounding plain because of built-up silt in the river beds, so water for irrigation
flowed into the fields by gravity. Once the water was on the fields, it could not readily
drain away because the fields were lower than the river. As the water evaporated, it not
only left its dissolved mineral salts behind, but also drew salts upward from lower levels
of the soil. Over time, the soil became toxic and would no longer support crops. By about
2300 B.C., agricultural production in Mesopotamia was reduced to a tiny fraction of what
it had been. Many fields were abandoned as essentially useless. Mesopotamian cuneiform
tablets tell of crop damage due to salts.