Climate Change Led To Collapse Of Ancient Indus Valley Civilization

Posted: Nov 14 2018, 10:50pm CST | by , Updated: Nov 14 2018, 10:54pm CST, in Latest Science News


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Climate Change Led to Collapse of Indus Ancient Indus Valley Civilization
Credit: S. Gupta

Researchers have found that a shift in temperatures and weather patterns over the Indus valley caused summer monsoon rains to gradually dry up and led to Harappans ultimate demise.

The Indus or Harappan Civilization thrived in the northwestern parts of South Asia more than 4,000 years ago. The ancient society that developed mainly in the Indus River Valley was marked by the construction of sophisticated cities and advanced culture.

During 1800 BCE, the Indus Civilization abandoned large cities. They settled in smaller villages in the Himalayan foothills and eventually disappeared. A new study provides evidence that ancient Indus civilization disintegrated in response to climate change. A shift in temperatures and weather patterns over the Indus valley caused summer monsoon rains to gradually dry up. The rainfall reductions made agriculture difficult or impossible near Harappan cities and forced people to resettle far away from the flowing river.

“Although fickle summer monsoons made agriculture difficult along the Indus, up in the foothills, moisture and rain would come more regularly,” said Liviu Giosan, a geologist at Woods Hole Oceanographic Institution (WHOI). “As winter storms from the Mediterranean hit the Himalayas, they created rain on the Pakistan side, and fed little streams there. Compared to the floods from monsoons that the Harappans were used to seeing in the Indus, it would have been relatively little water, but at least it would have been reliable.”

Finding direct evidence of this shift is difficult. But researchers were able to piece together climate records by taking samples from the ocean floor off Pakistan's coast. They examined the shells of single-celled plankton called foraminifera that they found in the sediments and uncovered deeper clues about region's climate.

"The seafloor near the mouth of the Indus is a very low-oxygen environment, so whatever grows and dies in the water is very well preserved in the sediment," said Giosan. "You can basically get fragments of DNA of nearly anything that's lived there."

Analysis revealed that strong winds bring nutrients from the deeper ocean to the surface, feeding a number of plant and animal life during winter monsoons. Weaker winds, on the other hand, provide fewer nutrients rest of the year, causing slightly less productivity in the waters offshore.

“The value of this approach is that it gives you a picture of the past biodiversity that you'd miss by relying on skeletal remains or a fossil record. And because we can sequence billions of DNA molecules in parallel, it gives a very high-resolution picture of how the ecosystem changed over time.” William Orsi, paleontologist and geobiologist at Ludwig Maximilian University of Munich, said.

Researchers believe that the collapse of Indus Civilization occurred gradually. The rains in the foothills seem to have been enough to hold settlements there for the next millennium, but even those would eventually dry up and contributed to their ultimate demise.


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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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