28 April 2023

Prolonged droughts likely ended the megacities of Indus Valley Civilisation: Study

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A study examining ancient rock formation from a cave in Uttarakhand suggests that a series of severe and lengthy droughts could be responsible for the decline of the cities of the Indus Civilisation. This arid period, which began about 4,200 years ago and persisted for more than two centuries, coincides with the restructuring of the Indus Civilization, which encompassed present-day India and Pakistan. 

The research, published in the journal “Communications Earth & Environment”, revealed that there were three prolonged droughts, each lasting between 25 and 90 years, during this dry period.

Indus Valley Civilisation (IVC)

• The Indus Valley Civilisation, also known as the Harappan Civilisation, was a Bronze Age civilisation that flourished in the Indus Valley region of South Asia from around 3300 BCE to 1300 BCE. It was one of the world's earliest urban civilisations and is believed to have been home to over five million people at its peak.
  
  
• The civilisation was spread across present-day northeastern Afghanistan, eastern Pakistan, and northwestern India. 
  
  
• The Indus Valley Civilisation had well-planned cities with well-organised streets, drainage systems, and public baths. 
  
  
• The cities were also known for their impressive architecture, including the Great Bath in Mohenjo-daro and the granary in Harappa.
  
  
• The people of the Indus Valley Civilisation were skilled in metallurgy, pottery, and weaving. They were also skilled in trade, with evidence of trade links with Mesopotamia, ancient Egypt, and the Persian Gulf region.
  
  
• The Indus script, which has yet to be deciphered, was used by the people of the Indus Valley Civilisation to write their language. The script was found on seals, pottery, and other artefacts.
  
  
• The decline of the Indus Valley Civilisation remains a topic of debate among historians and archaeologists. Theories include climate change, earthquakes, and invasion by outsiders. However, the exact cause of the decline is still unknown.

Study findings on the progressive transformation of environmental conditions in the Indus Civilization

• The study examined historic rainfall and droughts in the Indus Civilization.
  
  
• Evidence reveals a progressive transformation of the environment in which the Indus people lived.
  
  
• Researchers examined a stalagmite to chart historic rainfall and used Uranium-series dating for drought age and duration.
  
  
• The research identified distinct periods of below-average rainfall affecting both summer and winter seasons.
  
  
• The droughts during this period increased in duration and forced inhabitants to adapt for sustainability.
  
  
• Findings support existing evidence that the decline of Indus megacities was linked to climate change.
  
  
• During the transformation, larger urban sites were depopulated in favour of smaller rural settlements towards the eastern extent of the area occupied by Indus populations. 
  
  
• Agriculture shifted towards reliance on summer crops, especially drought-tolerant millets, and the population transitioned to a lifestyle that appears to have been more self-reliant.

The methodology used for the study

• The researchers examined growth layers in a stalagmite collected from a cave near Pithoragarh, Uttarakhand to chart historic rainfall. 
  
  
• They used a range of environmental tracers, including oxygen, carbon, and calcium isotopes, to obtain a reconstruction showing relative rainfall at seasonal resolution. 
  
  
• They also used high-precision Uranium-series dating to determine the age and duration of the droughts.

Other theories of the decline of the Indus Valley Civilization

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