SHILLONG, Sep 20: The Mawmluh Cave, locally known as Krem Mawmluh, is a geological treasure field. Inside the cave, rainwater has been slowly dripping from the ceiling in the same spots for over 1,000 years. With each drop, minerals in the water accumulate on the floor below, slowly growing into calcium carbonate towers known as stalagmites.
These stalagmites are more than geological wonders – like tree rings, their layers record the region’s rainfall history. They also carry a warning about the potential for catastrophic multiyear droughts in the future.
These stalagmites have revealed an accurate chronicle of severe and protracted droughts in India over the past 1,000 years coinciding with historical events like the abandonment of Fatehpur Sikri by the Mughals (between 1585 and 1610) due to water shortage, the infamous Chalisa Famine (1783-84) in north India and the Deccan Famine (1630–32).
The stalagmite records also corroborate droughts during the Durga Devi Famine of western India (1396-1407), at the start of India’s de-industrialisation after the end of the Mughal era, the Ming Dynasty (China) drought (1637–1643) and the Monsoon’s failure in 1877 when the all-India rainfall level dipped below 30% of the average.
The records of severe and protracted droughts during periods of weak monsoon lasting decades stored in natural rock deposits have exposed the vulnerability of the Indian summer monsoon, which could periodically “lock” into a drought-prone mode that might last for decades, the scientists said.
In contrast, meteorological data of the past 150 years showed only one instance of 10-15% rainfall shortage that lasted for three consecutive years (1985-87). Moreover, there are only five instances of subcontinent-wise monsoon failure, of which the most severe one was in 1877.
“This seemingly reassuring but rather myopic view currently informs the region’s present-day water resource infrastructure and contingencies policies, and discounts the possibility of protracted monsoon failures in the future,” the researchers cautioned in their study published in the Proceedings of the National Academy of Sciences on Monday.
“But historical documentary and proxy evidence show that Indian summer monsoon’s drought history in the past millennium was characterized by sub-decadal to multi-decadal periods of weaker monsoon that contained protracted droughts,” the researchers said.
Reconstructing India’s drought history between 1080 and 1905 by studying oxygen isotope records in the stalagmites of Krem Mawmluh, the scientists found chemical evidence of a 25-year-long drought period in the Mughal era between 1595 and 1620, which coincided with Emperor Akbar’s abandonment of Fatehpur Sikri.
The pieces of evidence also support the Deccan Famine — one of the most devastating mass mortality events in recorded Indian history; multi-year droughts in northern India between 1296 and 1316 under the reign of Alauddin Khilji and 11 drought-related famines in the late 18th century, six of which, including the well-known Chalisa and Doji Bara or Skull Famines, occurred between 1782 and 1792 with a combined estimated death toll in the excess of 1.1 crore, making it one of the deadliest decades in Indian history.
Even India’s de-industrialisation history in the 18th and 19th centuries has a climate link as loss of farm productivity led to the limited supply of grain, leading to an increase of wages in the weaving industry. This was coupled with a sharp rise in the prices of cotton.
“The early phase of de-industrialisation coincides with the most severe 30-year spell of the weak monsoon of the past millennium,” the researchers said.
While El Nino, a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean, is widely blamed for poor Monsoon in India, the researchers demonstrated that only in 20-50% of cases, the unusual warming of the Pacific could be held responsible for India’s historical droughts. The monsoon’s internal dynamics and other external forcing are equally critical.
(Credit: Proceedings of the National Academy of Sciences, USA)
