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A Millennium of Monsoon Failures, Droughts and Famines

The Asian Summer Monsoon (ASM) has made possible several complex civilizations to flourish over time. The monsoon domain of Asia extending from Oman to Australia affects almost 60 per cent of humanity today. Historical records have mentioned monsoon failures, droughts, famines and extreme flooding events in the past. Scientifically, the two most robust, continuous, terrestrial proxy rainfall archives are preserved in limestone cave deposits (stalagmite columns) and tree-ring growths (both of which record wet and dry phases or pluvials and droughts). Both archives require precise and very high accuracy geological dating techniques in conjunction with oxygen isotope analysis (the proxy for rainfall). During the past five years, the two archival techniques have been perfected to a degree that a yearly resolution of data is now possible with even a cross-check of dates.

Three cave proxy rainfall records from mainland Oman (Hoti), India (Danduk) and from China (the Wanxiang) have shown the past history of spatio-temporal variability of the monsoon. The Danduk record picked up periods of annually resolved, multi-decadal and centennial length episodes of reduced rainfall and drought during the past millennium, which coincided with several of India’s most devastating historical famines (e.g 879; 940-950; 1148-1159; 1344-1346 CE). The best known are two severe famines between 1350-1420, including the famous Durga Devi (1396-1409) that killed off millions of people in India. Comparing the cave proxy record with historical records, Chinese geologists constructed a record of Dynastic failures due to weakened monsoons, droughts, crop failures, famines and peasant revolts (e.g. the Tang- 850-940 CE; the late Yuan- 1350-1380 CE and Ming- 1580-1641 CE).

Decades that experienced the wettest and strongest monsoons of the past 1000 years coincided with the Northern Song Dynasty’s golden age of rich harvests, population recovery and social stability (960 – 1020 CE). This was clearly depicted in the paintings of that time. Interestingly, the demise of the Tang Dynasty and Maya Classic Periods were coeval (early 10th century) – both now related to extended drought phases, though far apart geographically. It is the amount of rainfall and its inter-regional pattern of variability, especially drought that is of importance to human populations.

Last month, the Tree-Ring Laboratory of the Lamont-Doherty Earth Observatory of Columbia University, USA (TRL-LDEO) released the Monsoon Asia Drought Atlas (MADA), which also provides an absolutely dated, annually resolved reconstruction of Asian monsoon spatio-temporal variability over the past 1000 years. MADA used tree-ring data from more than 300 sites of the forested regions of monsoon Asia to reconstruct an Index of relative drought and wetness for the region. The major finding of MADA is that historically recorded monsoon failures/excesses in the past 150 years have been exceeded in intensity and duration many times during the past millennium. The Atlas picked the Ming Dynasty Drought of 1638-1641- the worst in 500 years in northern China and its recorded final collapse in 1644; the Strange Parallels Drought (SPD 1756-1768), the East India Drought (EID 1790-1796) and the late Victorian Great Drought (VGD 1876-1878).

The EID that lasted six years coincided with one of the most severe El-Nino events of the late 18th century, which was felt worldwide and resulted in extensive civil unrest and socio-economic disaster. Its effect on India was devastating with several famines. The MADA record highlights its occurrence in the southernmost tip of India and extending to Sri Lanka, but there is no mention of it in the Sri Lankan records (or is there?). The drought is consistent with historical data for the region. The VGD also occurred during one of the most severe El-Nino events of the past 150 years. This drought was felt in much of India, Sri Lanka and Vietnam, parts of Indonesia, Thailand, Borneo and New Guinea according to MADA and is vaguely referred to in our recent historical records. Over 30 million people died across monsoon Asia from the famine (see Davis, M. 2001 –Late Victorian Holocausts, El-Nino famines and the making of the Third World. Versa, London). In the north-central region of Sri Lanka, Mannar and Mullaitivu, apparently there were no rice harvests for nine years and the coffee blight in Uva in the 1870s-1880s may have been due to this drought.

Thailand, Cambodia and Sri Lanka connections

The annually resolved MADA dendro-hydroclimatic record shows that there were persistent weak monsoons and extended decadal droughts in tropical South and Southeast Asia over the past 500-700 years. In the mid-late 14th and early 15th centuries, especially the long period from 1351-1368 CE that was coeval with severe decade long droughts alternating with strong monsoons and floods instigated the collapse of the Khmer civilization in Angkor (Cambodia). The droughts devastated the complicated water supply, management and distribution networks and agricultural base of Angkor, the largest medieval city of the time with upwards of 500,000 people, while flood episodes in turn destroyed the water control infrastructure. Droughts and floods at interdecadal scales are characteristic of the Asian monsoon.

From Sri Lanka’s point of view, it is imperative to mention two references to famines in the late 14th and early 15th century (Gampola Period?) from palm-leaf scrolls in Thailand, where it is mentioned that a contingent of priests from Chiang Mai, Thailand who came here in the early 1400s on a long pilgrimage were forced to return due to a severe drought/famine in Sri Lanka (but where?). This event, as far as is known went unrecorded (?) in our chronicles. The very disappointed priests lamented that they had to turn back as there was "mai mee khao gin" – there

A Millennium of Monsoon Failures,

was no rice to eat! The references to Sri Lanka are in Thai and from Phitsanulok in Thailand (Wyatt and Wichienkeeo, 1998- The Chiang Mai Chronicles and R.P. Thera, 1967- Jinakalamali Prakor). These droughts were recorded in the state chronicles of the Chao Praya Basin, which mention that the droughts extended west to India and Sri Lanka (see Buckley, B.M. et. al, 2010, Proc. Nat. Acad. Sc., Vol. 107(15): 6748-6752; Cook, E. et. al., 2010., Science, Vol. 328: 486-489).

The year 1403 is recorded by TRL as the most severe in the dendro-record (visit of monks?). Also, six of the twenty wettest years alternated with drought years during the latest 14th and early 15th centuries when the hydraulic infrastructure at Angkor was damaged by flood episodes, just after agricultural productivity was devastated by the preceding decadal droughts. The geological record of the floods is still preserved in the abandoned canal networks of Angkor. Despite over a century of research at Angkor, the ultimate causes of its collapse remained uncertain. The dearth of textual records after the 13th century hindered historical research. This has now been resolved by the detailed hydro-climatic record compiled from tree-ring data.

It was not that repeated droughts and floods were the ultimate cause of civilizational demise. The empire was already under severe pressure from wars, population expansions and social and political upheavals and perhaps even a shift from the Hindu faith, which bestowed unquestioned "godly" powers on the uncompromising rulers (Devaraja), to acceptance of Buddhism due to its more tolerant and democratic outlook that gradually diminished the authority of the weakened rulers. It went into ruin after about five centuries. The hydraulic city had the seeds of its own destruction with a constant battle with droughts and floods. It was a society totally dependent on the annual monsoonal flooding of its lowlands, which supported an extensive rice based agriculture-irrigation infrastructure. It just could not cope with the pressures on its infrastructure and the bureaucracy failed. Decadal droughts alternating with severe floods just pushed it over the edge and never recovered.

Despite the vicissitudes, quite amazingly, the Rajarata hydraulic civilization survived for over a thousand years – far more resilient than any known. It was even resuscitated after more than 600 years of abandonment and its basic infrastructure still functions today. Sri Lanka too had droughts and floods as has been recorded in the chronicles. However, the textual content and detail is very poor. For over 600 years (from 619-628 CE to 1237-1270 CE) there are no references to famines (droughts) when most of monsoon Asia experienced floods/droughts. There is no evidence whatsoever that Rajarata demise had climatic connotations before collapse. However, like in Angkor, it could have been pushed over the edge when the regimes were already weakened in succession by various other pressures and moved out to the southwest for a variety of reasons.

The Danduk cave record shows at least fifteen regional droughts between 1000-1500 CE. The two worst decadal droughts were in the late 14th and early 15th centuries that were also picked up by the dendro-records in the Columbia study quite independently. The references in the Thai records to a major drought in Sri Lanka in the early 1400s were mentioned earlier (same time as the Durgadevi drought in India and decadal droughts in Angkor?). A drought of similar magnitude and extent today with billions more people are unimaginable!

The palaeoclimate archives of monsoon Asia is a very active field of research today. The big gap is between Sri Lanka and Thailand (mostly ocean). However, the continental archives are being added to and refined. The LDEO-dendrochronology survey here was interrupted twice by the civil conflict and the 2004 tsunami event and good analytical material was not found. If the survey restarts and obtains good tree-ring dates, then new interpretations to our climate and social history are possible just as in the cases above.

Early chroniclers recorded only historical events that mattered in state affairs. Droughts and floods were not. It was more important to record alms-giving to priests and mass reciting of pirith to pray for rains. Unlike in India or China, the detail and textual content is lacking when describing famines. This author believes that droughts, famines and floods were as frequent in ancient Sri Lanka as in the rest of Asia and that the chroniclers were indifferent to natural disasters and did not bother to record them. They were only periodically recurring extreme events (as in Angkor) and in the natural order of things. Else, how come major droughts were "missed" here, but were recorded in Thailand and elsewhere? With smaller populations in Sri Lanka, the effects of a disaster may not have been very dramatic unlike in India or China where millions perished at a time. Perhaps our historians will enlighten us on these aspects!

* The author is a retired Professor of Geology

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