The Indus Valley, in present
Pakistan and northwest India, was home to Harappan Civilization
characterized by large, well-planned cities with advanced municipal
sanitation systems. “But the Harappans seemed to slowly lose their urban
cohesion, and their cities were gradually abandoned,” a report in the
Scientific American said.
“The link between this gradual decline and
climate has been tenuous because of a dearth of climate records from the
region,” the report added.
Yama Dixit, a paleoclimatologist at the
University of Cambridge, UK, and her colleagues obtained the new
evidence from the dried up bed of Kotla Dahar, an ancient lake 40 miles
east of the north-eastern edge of the Indus Valley area in Haryana,
“Our evidence suggests that it was the
most intense period of drought – probably due to frequent monsoon
failure – in the 5000 year-long period we have examined,” quoted The
Independent (UK) as said by Palaeoclimate scientist Professor David
Hodell of University of Cambridge.
Scientists and archaeologists detected the
climatic conditions by examining isotopic evidence from the shells of
snails that had lived between 6500 years ago and 1500 years ago.
The isotopic values of the calcium
carbonate in the snails’ shells reflected the isotopic value in the
water in the lakes at the time they lived.
Because water with oxygen 16 isotopes
evaporates more quickly than water with ‘heavier’ oxygen 18 isotopes,
the scientists were able to measure changes in evaporation rates over
time. This allowed them to identify the start and end of a previously
unknown 200 year-long severe drought in the north-west India region
which lasted from around 2100 BC to about 1900 BC.
In that period, the Indus Valley
'megacities' – some with populations of up to 100,000 – rapidly
declined. Populations shrank and an old urban civilization that had
lasted nearly 500 years did collapse.
“Archaeologists are really in a unique
position when investigating climate change in the past, because we
hopefully get to see what people were doing in the ‘before, during and
after’ phases. We therefore get an opportunity to investigate how
ancient populations responded to climatic and environmental change. How
did they cope with periods of water stress? Were their existing ways of
life resilient? Were they forced to adapt in order to survive, and if
so, precisely what did they do,” reported the Independent quoting
archaeologist, Dr. Cameron Petrie of University of Cambridge.
“By investigating responses to
environmental pressures and threats in the past, we can hopefully learn
from the past to engage with the public, and the relevant governmental
and administrative bodies to be more pro-active in issues such as the
management and administration of water supply, the balance of urban and
rural development, and even the importance of preserving cultural
heritage in the future,” Dr. Petrie added.
As scientists largely relate the climate
change phenomenon with green house gas (GHG) and carbon emission, Anil
Gupta, Director of the Wadia Institute of Himalayan Geology in Dehradun,
India, is quoted by Scientific American as questioning, “What drove this
climate change 4,100 years ago? We don’t see major changes in the North
Atlantic or in the solar activity at that time.”
The question raised by Anil Gupta
certainly alerts climate scientists to think if rapid urbanisation that
obviously causes environmental destruction has a bigger role in warming
and climate change.
However, the apprehension that climate
change at an extreme stage may collapse civilisations has become evident
from the fact that lack of monsoon did spell the end of the Indus Valley
We must take lessons from this to ensure
that our civilisation lasts longer.
The Independent (UK) and