Wednesday, May 30, 2012

Collapse Is The Norm Not The Exception

Ancient Egypt and Mesopotamia may be the best known of the first great urban cultures, but the largest was the Indus or Harappan civilization. This culture once extended over more than 386,000 square miles (1 million square kilometers) across the plains of the Indus River from the Arabian Sea to the Ganges, and at its peak may have accounted for 10 percent of the world population. The civilization developed about 5,200 years ago, and slowly disintegrated between 3,900 and 3,000 years ago — populations largely abandoned cities, migrating toward the east.

"They had cities ordered into grids, with exquisite plumbing, which was not encountered again until the Romans," Giosan told LiveScience. "They seem to have been a more democratic society than Mesopotamia and Egypt — no large structures were built for important personalitiess like kings or pharaohs."

Like their contemporaries in Egypt and Mesopotamia, the Harappans, who were named after one of their largest cities, lived next to rivers. "Until now, speculations abounded about the links between this mysterious ancient culture and its life-giving mighty rivers," Giosan said.

Now Giosan and his colleagues have reconstructed the landscape of the plain and rivers where this long-forgotten civilization developed. Their findings now shed light on the enigmatic fate of this culture.
"Our research provides one of the clearest examples of climate change leading to the collapse of an entire civilization," Giosan said.

Initially, the monsoon-drenched rivers the researchers identified were prone to devastating floods. Over time, monsoons weakened, enabling agriculture and civilization to flourish along flood-fed riverbanks for nearly 2,000 years. Eventually, these monsoon-based rivers held too little water and dried, making them unfavorable for civilization.

"The Harappans were an enterprising people taking advantage of a window of opportunity — a kind of "Goldilocks civilization," Giosan said. Eventually, over the course of centuries, Harappans apparently fled along an escape route to the east toward the Ganges basin, where monsoon rains remained reliable.

"We can envision that this eastern shift involved a change to more localized forms of economy — smaller communities supported by local rain-fed farming and dwindling streams," Fuller said. "This may have produced smaller surpluses, and would not have supported large cities, but would have been reliable."
This change would have spelled disaster for the cities of the Indus, which were built on the large surpluses seen during the earlier, wetter era. The dispersal of the population to the east would have meant there was no longer a concentrated workforce to support urbanism.

"Cities collapsed, but smaller agricultural communities were sustainable and flourished," Fuller said. "Many of the urban arts, such as writing, faded away, but agriculture continued and actually diversified."
It remains uncertain how monsoons will react to modern climate change. "If we take the devastating floods that caused the largest humanitarian disaster in Pakistan's history as a sign of increased monsoon activity, than this doesn't bode well for the region," Giosan said. "The region has the largest irrigation scheme in the world, and all those dams and channels would become obsolete in the face of the large floods an increased monsoon would bring."
Huge Ancient Civilzation's Collapse Explained (Live Science)

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