Decline of Indus Valley Civilisation

A recent study claims that the Indus Valley Civilisation (IVC) declined not due to one catastrophic event, but due to centuries-long, recurring droughts that progressively weakened its cities, rivers, agriculture, and social structures.

Key Findings from the Study

• Central Conclusion:
  • The study indicates that the IVC did not collapse suddenly due to one catastrophic event.
  • Instead it reveals Harappa and other major IVC settlements were affected by a series of multi-decadal droughts between 3000–1000 BCE.
• Climate Reconstruction: Researchers used paleoclimate records (stalactites, stalagmites, lake levels) and climate model simulations to reconstruct rainfall and temperature patterns of the period.

Reasons for Decline of Civilisation

• Recurring Drought Cycles: Four major drought events, each lasting over 85 years, occurred between 2425–1400 BCE.
  • The most severe drought peaked around 1733 BCE, lasted ~164 years, and impacted the entire region.
• Hydrological Collapse: Prolonged drought led to Shrinking lakes and playas, Declining river flows, Soil desiccation, Reduced navigability, hurting trade.
• Climate Shift in the Pacific:
  • Early IVC prosperity coincided with La Niña-like conditions (3000–2475 BCE), causing wetter-than-modern monsoon seasons.
  • As the tropical Pacific warmed, annual rainfall dropped by 10–20%, and temperatures rose by 0.5°C, amplifying arid conditions.

Social and Economic Consequences

• Agricultural Stress: Drought made farming difficult, especially for settlements far from perennial rivers.
  • Adaptive Agricultural Practices: Harappans responded by switching crops, diversifying production, and shifting to drought-resilient farming.
  • Archaeo-botanical evidence shows a shift from wheat and barley to drought-resistant millets, indicating attempts to cope with aridity.
• Migration and Dispersal: Communities were forced to relocate repeatedly, reshaping the distribution of settlements along the Indus and its tributaries.
  • They diversified trade routes and moved settlements to more water-secure areas.
• Governance Strain: Reduced food supply and weak political structures combined with climatic pressures, pushing society toward decline and fragmentation.
• De-urbanisation:  The final century-long drought (3531–3418 BCE) coincides with archaeological evidence of large cities being abandoned and populations dispersing into smaller rural clusters.

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Theories of Decline of the Indus Valley Civilization

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