section_path: Late Harappan/Climate change and drought
section_name: Climate change and drought
paragraph_text: Climate change and drought
  
  Suggested contributory causes for the localisation of the IVC include changes in the course of the river, and climate change that is also signaled for the neighboring areas of the Middle East. As of 2016 many scholars believe that drought, and a decline in trade with Egypt and Mesopotamia, caused the collapse of the Indus civilisation. The climate change which caused the collapse of the Indus Valley Civilisation was possibly due to "an abrupt and critical mega-drought and cooling 4,200 years ago ", which marks the onset of the Meghalayan Age, the present stage of the Holocene.
  
  The Ghaggar-Hakra system was rain-fed, and water-supply depended on the monsoons. The Indus Valley climate grew significantly cooler and drier from about 1800 BCE, linked to a general weakening of the monsoon at that time. The Indian monsoon declined and aridity increased, with the Ghaggar-Hakra retracting its reach towards the foothills of the Himalaya, leading to erratic and less extensive floods that made inundation agriculture less sustainable.
  
  Aridification reduced the water supply enough to cause the civilisation's demise, and scatter its population eastward. According to Giosan et al. (2012), the IVC residents did not develop irrigation capabilities, relying mainly on the seasonal monsoons leading to summer floods. As the monsoons kept shifting south, the floods grew too erratic for sustainable agricultural activities. The residents then migrated towards the Ganges basin in the east, where they established smaller villages and isolated farms. The small surplus produced in these small communities did not allow the development of trade, and the cities died out.