Climate Change

Harappa, Rakhigarhi, Dholavira: 200 years of droughts may have erased these Indus megacities, says study

The prolonged droughts forced the civilisation to reorganise their settlements & switch to drought-resilient crops

By Preetha Banerjee
Published: Thursday 27 April 2023
Photo: iStock_

Climate change has long been associated with the fall of the ancient Indus civilisation, and a new study of evidence from a Himalayan cave established that prolonged droughts during the Bronze Age may have snuffed out the life of the people in the region. 

Droughts that began 4,200 years ago gripped the civilisation spread over present-day Pakistan and India, and went on for over two centuries, the University of Cambridge report published in the journal Nature showed. 

The scientists recovered a stalagmite — vertical mass of mineral deposits rising from the floor of caves and caused by water dripping — from a cave near Pithoragarh district in India’s Uttarakhand. They studied the layers of this stalagmite to assess relative seasonal rainfall over thousands of years. “They also used high-precision Uranium-series dating to get a handle on the age and duration of the droughts,” a University of Cambridge article on the study noted. 

They found indications of three droughts lasting 25-90 years each during the dry 200 years. This period also coincided with the time when the civilisation was building cities, according to the authors of the report. 

The team identified distinct periods of below-average rainfall in both the summer and winter seasons, according to lead author of the research Alena Giesche, a PhD scholar at Cambridge’s earth sciences department. 

Much like what countries across the world are experiencing today due to climate change — the protracted droughts severely affected food systems and habitation patterns, among other things, the researchers found. This forced the people of the Indus Civilisation to make systemic changes to adapt to the changing environment.

They reorganised their large cities and moved towards the east of the region in smaller rural settlements, the report Recurring summer and winter droughts from 4.2-3.97 thousand years ago in north India showed. 

They also had to make changes to their agricultural practices – relying more on drought-resilient crops such as millets, according to the authors. 

The population adopted a more self-reliant lifestyle as a means of climate adaptation, the findings of the study indicated. 

Comparing climatic and archaeological records wasn’t also easy and lacked accuracy but things have improved, according to David Hodell, study co-author from Cambridge’s department of earth sciences. “Palaeoclimate records are becoming progressively better at refining changes in rainfall on a seasonal and annual basis, which directly affects people's decision making.” 

The team will now attempt to make similar climate reconstructions for the western parts of the Indus River region, “where the winter rainfall system becomes more dominant than the Indian Summer Monsoon”, according to the university article.

“Currently, we have a huge blind spot on our maps extending across Afghanistan and Pakistan, where the Indian summer monsoon and the Westerlies interact,” Sebastian Breitenbach, co-author and palaeoclimatologist at Northumbria University, was quoted as saying in the Cambridge story. “Sadly, the political situation is unlikely to allow for this kind of research in the near future."

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