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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 PithoragarhUttarakhand 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




Aryan Invasion Theory

Max Mueller, Mortimer Wheeler

Suggests that an invasion by the Aryan people from the north brought new technologies and ideas that led to the collapse of the Indus Valley Civilization.

Environmental Factors

Robert Raikes, R.D. Oldham

Argues that environmental factors, such as climate change, drought, and floods, played a major role in the decline of the Indus Valley Civilization.

Internal Decline

S.R. Rao

Proposes that the decline of the Indus Valley Civilization was caused by internal factors such as political instability, corruption, and economic decline.

Natural Disaster Theory

D.P. Agrawal

Suggests that a major natural disaster, such as an earthquake, was responsible for the decline of the Indus Valley Civilization.

Integration with Vedic Culture

David Frawley

Suggests that the decline of the Indus Valley Civilization was not a collapse but rather a transformation into the Vedic culture of ancient India.

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Fact File

SC modifies judgement on eco-sensitive zones around protected forests

  • Recently, the Supreme Court revised its ruling to make it mandatory to establish eco-sensitive zones (ESZ) around protected forests, national parks, and wildlife sanctuaries across the country, with a minimum radius of one kilometre.

  • The SC has ruled that ESZ cannot have a uniform standard throughout the country and must be customizedaccording to the specific requirements of each protected area. 

  • On June 3, 2022, the Supreme Court had mandated a one-kilometre buffer zone around protected areas to function as a "shock absorber".

Eco-sensitive zones

  • Eco-sensitive zones are areas identified as ecologically important and sensitive in terms of conservation and protection of natural resources.

  • They are usually designated around protected areas such as national parks, wildlife sanctuaries, and biosphere reserves.


  • To protect and conserve the ecological and environmental characteristics of the area, including wildlife, biodiversity, and natural resources.

  • To act as buffer zones to prevent human activities from causing harm to the protected area.

  • To ensure the sustainable development of the area, while also safeguarding the ecological and environmental values.

Prohibited or restricted activities

  • Mining, industries, commercial tourism, and construction activities that are not compatible with the conservation and protection of the area are prohibited or restricted.

  • The use of chemicals, fertilizers, and pesticides that can harm the environment and wildlife is also regulated.


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