The decline of the Indus River Valley Civilization can be attributed to various factors related to climate change. One significant cause was the decrease in the intensity of summer monsoons around 2500 BCE. This reduction in monsoon strength led to increased drought conditions, which severely impacted agricultural productivity.
As for the effects of this climatic shift, three notable consequences followed:
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Agricultural Decline: The reliance of the Harappan civilization on regular flooding for irrigation meant that with weaker monsoons and reduced water availability, crops could not be sustained. This agricultural decline led to food shortages, forcing communities to seek more reliable water sources.
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Migration and Urban Decline: With diminishing agricultural output, people began migrating eastward to the Himalayan foothills, where they transitioned from thriving urban centers to small farming villages. This significant demographic shift further contributed to the decay of urban infrastructure and societal complexity, as communities dispersed.
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Cultural Shift and Ultimate Demise: The eventual drying up of winter monsoons in the foothills also had a detrimental impact, leading to the further decline of these new settlements and unattainable living conditions. The combination of environmental stressors and possible socio-political shifts, such as the migration of Indo-Aryan peoples into the region, culminated in the ultimate demise of the Indus River Valley Civilization by around 1800 BCE.
These interconnected causes and effects illustrate how climate change played a critical role in shaping the trajectory of this ancient civilization.