Climate Change led to Collapse of Ancient Indus Civilisation

30 May 2012

Morphology of the western Indo-Gangetic plain with interfluves (in gray mask), incised valleys (no mask), terrace edges (as dashed black lines), and active and fossilized river channels (in blue).

A new study, involving the Institute's Dorian Fuller, published this month in PNAS, provides evidence that climate change was a key ingredient in the collapse of the great Indus or Harappan Civilisation almost 4000 years ago.

The ground-breaking collaborative research project, which combines the latest archaeological evidence with state-of-the-art geoscience technologies, also resolves a long-standing debate over the source and fate of the Sarasvati, the sacred river of Hindu mythology.

Once extending more than 1 million square kilometers across the plains of the Indus River from the Arabian Sea to the Ganges, over what is now Pakistan, northwest India and eastern Afghanistan, the Indus civilization was the largest—but least known—of the first great urban cultures that also included Egypt and Mesopotamia. Like their contemporaries, the Harappans, named for one of their largest cities, lived next to rivers owing their livelihoods to the fertility of annually watered lands.

Today, numerous remains of the Harappan settlements are located in a vast desert region far from any flowing river. In contrast to Egypt and Mesopotamia, which have long been part of the Western classical canon, this amazingly complex culture in South Asia with a population that at its peak may have reached 10 percent of the world’s inhabitants, was completely forgotten until 1920’s. Since then, a flurry of archaeological research in Pakistan and India has uncovered a sophisticated urban culture with myriad internal trade routes and well-established sea links with Mesopotamia, standards for building construction, sanitation systems, arts and crafts, and a yet-to-be deciphered writing system. 

Settlements on morphological units of the western Indo-Gangetic plain

Research, led by Liviu Gosan, a geologist with the Woods Hole Oceanographic Institution (WHOI), was conducted between 2003 and 2008 in Pakistan, from the coast of the Arabian Sea into the fertile irrigated valleys of Punjab and the northern Thar Desert. The international team included scientists from the US, UK, Pakistan, India, and Romania with specialties in geology, geomorphology, archaeology, and mathematics. By combining satellite photos and topographic data collected by the Shuttle Radar Topography Mission (SRTM), the researchers prepared and analyzed digital maps of landforms constructed by the Indus and neighboring rivers, which were then probed in the field by drilling, coring, and even manually-dug trenches. Collected samples were used to determine the sediments’ origins, whether brought in and shaped by rivers or wind, and their age, in order to develop a chronology of landscape changes. 

  • “Once we had this new information on the geological history, we could re-examine what we know about settlements, what crops people were planting and when, and how both agriculture and settlement patterns changed. This brought new insights into the process of eastward population shift, the change towards many more small farming communities, and the decline of cities during late Harappan times.” [Dorian Fuller]

The new study suggests that the decline in monsoon rains led to weakened river dynamics, and played a critical role both in the development and the collapse of the Harappan culture, which relied on river floods to fuel their agricultural surpluses.

From the new research, funded by the National Science Foundation, the Leverhulme Trust, Woods Hole Oceanographic Institution (WHOI), the University of Aberdeen, and Louisiana State University, a compelling picture of 10,000 years of changing landscapes emerges.

Media reporting of the research