Editing Indus Valley Civilisation (section)

===Climate change and drought===
{{See also|Bond event|4.2-kiloyear event}}
Suggested contributory causes for the localisation of the IVC include changes in the course of the river,<ref>David Knipe (1991), ''Hinduism''. San Francisco: Harper</ref> and [[climate change]] that is also signaled for the neighboring areas of the Middle East.<ref>{{cite news |url=http://phys.org/news/2014-02-decline-bronze-age-megacities-linked.html |title=Decline of Bronze Age 'megacities' linked to climate change |date=February 2014 |website=phys.org |access-date=31 October 2015 |archive-date=22 June 2018 |archive-url=https://web.archive.org/web/20180622164659/https://phys.org/news/2014-02-decline-bronze-age-megacities-linked.html |url-status=live }}</ref><ref>{{Cite journal|last=Marris|first=Emma|date=3 March 2014|title=Two-hundred-year drought doomed Indus Valley Civilization|url=https://www.nature.com/articles/nature.2014.14800|journal=Nature|language=en|doi=10.1038/nature.2014.14800|s2cid=131063035|issn=1476-4687|access-date=14 February 2023|archive-date=24 January 2023|archive-url=https://web.archive.org/web/20230124002339/https://www.nature.com/articles/nature.2014.14800|url-status=live}}</ref> {{As of| 2016}} many scholars believe that drought, and a decline in trade with Egypt and Mesopotamia, caused the collapse of the Indus civilisation.<ref name="Science">{{cite journal|date=6 June 2008|title=Indus Collapse: The End or the Beginning of an Asian Culture?|journal=Science Magazine|volume=320|pages=1282–1283|doi=10.1126/science.320.5881.1281 | last1 = Lawler | first1 = A.|issue=5881|pmid=18535222|s2cid=206580637}}</ref> The climate change which caused the collapse of the Indus Valley Civilisation was possibly due to "an abrupt and critical [[4.2-kiloyear event|mega-drought and cooling 4,200&nbsp;years ago]]", which marks the onset of the [[Meghalayan|Meghalayan Age]], the present stage of the [[Holocene]].<ref>{{cite web |publisher=International Commission on Stratigraphy |title=Collapse of civilizations worldwide defines youngest unit of the Geologic Time Scale |url=http://www.stratigraphy.org/index.php/ics-news-and-meetings/119-collapse-of-civilizations-worldwide-defines-youngest-unit-of-the-geologic-time-scale |series=News and Meetings |access-date=15 July 2018|archive-date=15 July 2018|archive-url=https://web.archive.org/web/20180715004024/http://www.stratigraphy.org/index.php/ics-news-and-meetings/119-collapse-of-civilizations-worldwide-defines-youngest-unit-of-the-geologic-time-scale}}</ref>

The [[Ghaggar-Hakra]] system was rain-fed,{{sfn|Clift|Carter|Giosan|Durcan|2012}}{{refn|group=lower-alpha|Geological research by a group led by [[Peter Clift]] investigated how the courses of rivers have changed in this region since 8000&nbsp;years ago, to test whether climate or river reorganisations caused the decline of the Harappan. Using U-Pb dating of zircon sand grains they found that sediments typical of the Beas, Sutlej, and Yamuna rivers (Himalayan tributaries of the Indus) are actually present in former Ghaggar-Hakra channels. However, sediment contributions from these glacial-fed rivers stopped at least by 10,000&nbsp;years ago, well before the development of the Indus civilisation.{{sfn|Clift|Carter|Giosan|Durcan|2012}}}}<ref name="Tripathi_2004"/>{{refn|group=lower-alpha|Tripathi et al. (2004) found that the isotopes of sediments carried by the Ghaggar-Hakra system over the last 20&nbsp;thousand years do not come from the glaciated Higher Himalaya but have a sub-Himalayan source, and concluded that the river system was rain-fed. They also concluded that this contradicted the idea of a Harappan-time mighty "Sarasvati" river.<ref name="Tripathi_2004">{{cite journal |first1=Jayant K. |last1=Tripathi |author2=Bock, Barbara |author3=Rajamani, V. |author4=Eisenhauer, A. |title=Is River Ghaggar, Saraswati? Geochemical Constraints |journal=Current Science |volume=87 |issue=8 |date=25 October 2004 |url=http://www.ias.ac.in/currsci/oct252004/1141.pdf |archive-url=https://web.archive.org/web/20041225113356/http://www.ias.ac.in/currsci/oct252004/1141.pdf |url-status=dead |archive-date=25 December 2004}}</ref>}} and water-supply depended on the monsoons. The Indus Valley climate grew significantly cooler and drier from about 1800&nbsp;BCE, linked to a general weakening of the [[monsoon]] at that time.{{Sfn|Giosan|Clift|Macklin|Fuller|2012}} The Indian monsoon declined and aridity increased, with the Ghaggar-Hakra retracting its reach towards the foothills of the Himalaya,{{Sfn|Giosan|Clift|Macklin|Fuller|2012}}<ref>{{cite news |url=http://green.blogs.nytimes.com/2012/05/29/an-ancient-civilization-upended-by-climate-change/?_r=0 |title=An Ancient Civilization, Upended by Climate Change |author=Rachel Nuwer |author-link=Rachel Nuwer |date=28 May 2012 |access-date=29 May 2012 |newspaper=New York Times |series=LiveScience |archive-date=7 October 2019 |archive-url=https://web.archive.org/web/20191007120514/https://green.blogs.nytimes.com/2012/05/29/an-ancient-civilization-upended-by-climate-change/?_r=0 |url-status=live }}</ref><ref>{{cite news |url=http://www.livescience.com/20614-collapse-mythical-river-civilization.html |title=Huge Ancient Civilization's Collapse Explained |author=Charles Choi |date=29 May 2012 |access-date=18 May 2016 |newspaper=New York Times |archive-date=1 May 2020 |archive-url=https://web.archive.org/web/20200501194840/https://www.livescience.com/20614-collapse-mythical-river-civilization.html |url-status=live }}</ref> leading to erratic and less extensive floods that made inundation agriculture less sustainable.

Aridification reduced the water supply enough to cause the civilisation's demise, and scatter its population eastward.{{sfn|Madella|Fuller|2006}}{{sfn|MacDonald|2011}}<ref name=brooke-2014>{{harvnb|Brooke|2014|p=[https://books.google.com/books?id=O9TSAgAAQBAJ&pg=PA296 296]}}</ref><!-- **START OF NOTE** -->{{refn|group=lower-alpha|name="Note-Brooke"|{{harvp|Brooke|2014|p=296}}. "The story in Harappan India was somewhat different (see Figure 111.3). The Bronze Age village and urban societies of the Indus Valley are something of an anomaly, in that archaeologists have found little indication of local defense and regional warfare. It would seem that the bountiful monsoon rainfall of the Early to Mid-Holocene had forged a condition of plenty for all and that competitive energies were channeled into commerce rather than conflict. Scholars have long argued that these rains shaped the origins of the urban Harappan societies, which emerged from Neolithic villages around 2600 BC. It now appears that this rainfall began to slowly taper off in the third millennium, at just the point that the Harappan cities began to develop. Thus it seems that this "first urbanisation" in South Asia was the initial response of the Indus Valley peoples to the beginning of Late Holocene aridification. These cities were maintained for 300 to 400 years and then gradually abandoned as the Harappan peoples resettled in scattered villages in the eastern range of their territories, into Punjab and the Ganges Valley....' 17 (footnote):<br />
(a) {{harvp|Giosan|Clift|Macklin|Fuller|2012}};<br />
(b) {{harvp|Ponton|Giosan|Eglinton|Fuller|2012}};<br />
(c) {{harvp|Rashid|England|Thompson|Polyak|2011}};<br />
(d) {{harvp|Madella|Fuller|2006}};<br />Compare with the very different interpretations in <br />
(e) {{harvp|Possehl|2002|pp=[https://books.google.com/books?id=pmAuAsi4ePIC&pg=PA239 237–245]}}<br />
(f) {{harvp|Staubwasser|Sirocko|Grootes|Segl|2003}}}}<!-- **END OF NOTE** --> According to Giosan et al. (2012), the IVC residents did not develop irrigation capabilities, relying mainly on the seasonal monsoons leading to summer floods. As the monsoons kept shifting south, the floods grew too erratic for sustainable agricultural activities. The residents then migrated towards the Ganges basin in the east, where they established smaller villages and isolated farms. The small surplus produced in these small communities did not allow the development of trade, and the cities died out.<ref>{{cite news |author=Thomas H. Maugh II |url=http://www.latimes.com/news/science/sciencenow/la-sci-sn-indus-harappan-20120528,0,1127932.story |title=Migration of monsoons created, then killed Harappan civilization |date=28 May 2012 |access-date=29 May 2012 |newspaper=Los Angeles Times |archive-date=19 November 2012 |archive-url=https://web.archive.org/web/20121119111817/http://www.latimes.com/news/science/sciencenow/la-sci-sn-indus-harappan-20120528,0,1127932.story |url-status=live }}</ref><ref>{{Cite journal |display-authors=4 |last1=Dixit |first1=Yama |last2=Hodell |first2=David A.|last3=Giesche|first3=Alena|last4=Tandon|first4=Sampat K. |last5=Gázquez|first5=Fernando |last6=Saini|first6=Hari S.|last7=Skinner|first7=Luke C.|last8=Mujtaba |first8=Syed A.I.|last9=Pawar|first9=Vikas|date=9 March 2018|title=Intensified summer monsoon and the urbanization of Indus Civilization in northwest India|journal=Scientific Reports|volume=8|issue=1|page=4225 |doi=10.1038/s41598-018-22504-5|pmid=29523797|pmc=5844871|issn=2045-2322|bibcode=2018NatSR...8.4225D}}</ref>