Why India could disappear like Indus valley civilization once did

History has a way of repeating itself and we might just be in the throes of one such repetition: the fall of the Indus Valley civilization. A study by researchers at Indian Institute of Tropical Meteorology (IITM) has revealed that an interplay of climate factors, strikingly similar to those affecting modern-day monsoons, likely led to the collapse of the civilization over 4,000 years ago. By analysing ancient cave formations (speleothems) from Gupteswar and Kadapa caves, the study found how reduced solar radiation, El Niño, southward migration of the Intertropical Convergence Zone (ITCZ), and a negative phase of the Indian Ocean Dipole (IOD) collectively weakened the monsoon, triggering the downfall of the ancient civilization.Granted, those early Indians probably didn’t have the gargantuan wheels of modern-day industrialisation chugging along, spewing carbon into the air, but they did have their own version of an agricultural revolution leading to deforestation. This could be one of many, many factors leading to the potentially fatal climate change. medium113422872Researchers Ipsita Roy and Naveen Gandhi from the Center for Climate Change Research at IITM took a deep dive to find out. But first, a little background.A truly ancient civilizationThe Indus Valley civilization included major urban centres like Harappa and Mohenjo-Daro, along with settlements such as Dholavira, Lothal, and Rakhigarhi.Scientists believe that it spread over a vast expanse of India — stretching to the banks of the now “lost” Saraswati river or the Ghaggar-Hakra river — but this has not been studied enough because what we know so far is based on British excavations.In fact, in 2016, researchers from IIT-Kharagpur and Archaeological Survey of India (ASI) uncovered evidence that the Indus Valley civilization is at least 8,000 years old, and not 5,500 years old, taking root well before the Egyptian (7000BC to 3000BC) and Mesopotamian (6500BC to 3100BC) civilizations. They also found evidence of a pre-Harappan civilization that existed for at least 1,000 years before this. 113422272The late Harappan phase witnessed large-scale de-urbanisation, drop in population, abandonment of established settlements, violence and even the disappearance of the Harappan script, the researchers said. Their study revealed that the monsoon started weakening 7,000 years ago but, surprisingly, the civilization did not disappear. The Indus Valley people were very resolute and flexible and continued to evolve even in the face of declining monsoon. The people shifted their crop patterns from large-grained cereals like wheat and barley during the early part of the intensified monsoon to drought-resistant species like rice in the latter part. As the yield diminished, the organised large storage system of the Mature Harappan period gave way to more individual household-based crop processing and storage systems that acted as a catalyst for the de-urbanisation of the civilization rather than an abrupt collapse, they said.What does the monsoon have to do with it?The Indian summer monsoon is crucial for India’s water supply, agriculture, and overall economy, notes the IITM study. It says cave formations, like stalactites and stalagmites, can provide detailed records of past climates. The study examines trace elements (tiny amounts of certain metals) in cave formations from two caves in India to understand climate changes over the last 7,000 years. medium113427376The first is the Gupteswar cave in Odisha’s Koraput district. The cave is ideal for paleoclimate studies because it’s secluded from human interference. The region receives about 1500 mm of annual rainfall, mostly during the summer monsoon. The second cave—Kadapa cave in Andhra Pradesh’s Rayalaseema—is also quite secluded, with around 500 mm of annual rainfall.Stalactites and stalagmites were collected from both caves and the age of the samples was determined using a method that measures the decay of uranium. Tiny samples were drilled from the cave formations and analysed for various trace elements like magnesium (Mg), barium (Ba), strontium (Sr), and others. medium113422637“What’s fascinating is that the climate patterns we see affecting monsoons today were at play thousands of years ago, shaping the fate of entire civilizations,” said Naveen Gandhi, the lead researcher from IITM.The findingsThe changes in trace elements suggest that the climate in this region has gone through several wet and dry phases. These changes are likely influenced by shifts in the Intertropical Convergence Zone (ITCZ)—a low-pressure area near the equator where the trade winds from the Northern and Southern Hemispheres meet—solar activity, and ocean temperatures. medium113427409The study found that around 4,200 years ago, ITCZ — a critical weather system often described as a “rain belt” — shifted southward, depriving the Indus region of crucial rainfall. Simultaneously, a negative phase of the IOD cooled the eastern Indian Ocean, further weakening the monsoon by reducing moisture transport to the subcontinent. Indian Ocean Dipole (IOD) is a climate pattern affecting the Indian Ocean. These factors, combined with a period of reduced solar radiation and increased El Niño events, led to prolonged droughts in the Indus Valley.Social implicationsThe study identified two significant climate events: 4,200 years ago and 2,800 years ago. medium113422940There was a significant decline in precipitation 4,200 years ago, likely due to the above-mentioned shifts in the ITCZ and IOD. These changes weakened the Indian summer monsoon. The climate event 2,800 years ago was linked to low solar activity and increased El Niño-Southern Oscillation (ENSO) activity. This period also experienced a southward shift of the ITCZ, further weakening the monsoon.The agrarian revolution, which involved the domestication of animals and the development of agriculture, likely contributed to climate change. Changes in land use, such as deforestation and the expansion of agricultural lands, would have increased the albedo (the proportion of light reflected by a surface) of inhabited areas, particularly in regions prone to desertification. medium113423104These human-induced changes could have intensified the dry conditions around 4,200 years ago, further altering precipitation patterns and impacting civilizations.As conditions worsened, people would have migrated eastward towards the more fertile and water-rich Ganga plains. This migration is supported by archaeological evidence showing a shift in settlement patterns during this period. It led to the development of new settlements and the spread of cultural practices.In response to the prevailing dry conditions, communities in southern India constructed water-retaining rock pools during the Iron Age (1000-500 BCE). These structures were crucial for storing water during dry periods, indicating an adaptation to the changing climate. medium113427430Other civilizations affectedThe Indus Valley wasn’t the only civilization that was affected by these changing weather patterns. The Vedic civilizations, which flourished on the banks of the river Saraswati between 2,500 and 4,000 years ago, also experienced significant changes during this period. The decline in rainfall likely contributed to the decline of these civilizations, although the exact causes are still not fully understood.Similar climatic conditions affected the Akkadian empire in Mesopotamia. The severe drought around 4,200 years ago caused widespread famine and social unrest, leading to the collapse of the empire. Furthermore, the reduction in the flow of the Nile River due to decreased rainfall also impacted the Egyptian kingdom, contributing to its decline during this period. medium113427452With inputs from stories by Jhimli Mukherjee PandeyAI Images generated by Labanya Maitra