Around over 4,000 years ago, it was found that the Harappa culture flourished in the Indus River Valley which is, currently, the modern Pakistan and north-western India with fancy cities and advanced culture. By 1800 BCE, this advanced culture had abandoned their cities, moving instead to smaller villages in the Himalayan foothills.
Not so famous but the Indus civilization was known for being the largest and the first great urban cultures that also included Egypt and Mesopotamia. The Harappans were dependent on river floods to fuel their agricultural surpluses. Today, numerous remains of the Harappan settlements are located in a vast desert region far from any flowing river. A new study from the Woods Hole Oceanographic Institution (WHOI) found evidence the Harappans left due to this climate change and decided to resettle far away from the floodplains of the Indus. Liviu Giosan, a geologist at WHOI and lead author, reported that around 2500 BCE, a shift in temperatures was encountered and weather patterns changed over the Indus valley caused summer monsoon rains. It slowly and slowly starting to dry that further affected the agriculture and made things difficult or impossible near Harappan cities. When the agriculture became tough for the Harappans along the Indus, up in the foothills, moisture and rain was happening regularly and winter storms from the Mediterranean hit the Himalayas, the Harappans could not rely on this and decided to switch from relying on Indus floods to rains near the Himalaya in order to water crops which was difficult to find in soil samples. Hence, Giosan and his team focused on sediments from the ocean floor off Pakistan's coast. He and his team examined the core samples at several sites in the Arabian Sea I order to analyse and understand which ones developed in the summer, and which in winter in order to focus on deeper clues to the region's climate. They observed during winter monsoons, strong winds bring nutrients from the deeper ocean to the surface, feeding a surge in plant and animal life whereby weaker winds, at other times of year, provided fewer nutrients, causing slightly less productivity in the waters offshore. As per the DNA, the pair found that winter monsoons seemed to become stronger and summer monsoons weaker during the later years of the Harappan civilization, corresponding with the move from cities to villages. No one knows whether Harappans migrated within months or over centuries but the rains in the foothills were enough to hold the rural Harappans over for the next millennium. Migration from Syria and Africa has some roots in climate change and the rise in sea level due to climate change can lead to huge migrations from low lying regions like Bangladesh, or from hurricane-prone regions in the southern U.S.
By: Anuja Arora