Societal Adaptation to Climate Change:
Integrating Palaeoclimatological Data with Historical and Archaeological Evidences

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  3. PR
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  5. FR②
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  8. FR⑤

2018

PL Photo Project Leader

NAKATSUKA Takeshi

RIHN

Professor Nakatsuka’s specialties are palaeoclimatology and isotope biogeochemistry. Since his early career as a graduate student, he has been using nitrogen isotopes to study long-term variations of climate and its impacts on oceanic biogeochemical cycles. Recently, he changed his main research area from oceans to land and focused on using tree-ring oxygen isotopes to examine the relationship between climate change and human history. Investigating periodicity of climate during the last three millennia in Japan and the world, he now hypothesizes that past human societies were often damaged by multi-decadal climate variations as they were caught in a cycle of over-adaptation and subsequent failure of adaptation.

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Sub Leader
KAMATANI KaoruRitsumeikan University/RIHN Visiting Associate Professor
Researchers at RIHN
ITO KeisukeResearcher
LI ZhenResearcher
TESHIMA MikaResearch Associate
KURIU HarumiResearch Associate
MIZUMA SakikoResearch Associate
MIURA TomokoResearch Associate
Main Members
SANO MasakiWaseda University
WAKABAYASHI KunihikoDoshisha University
HIGAMI NoboruAichi Prefectural Center for Archaeological Operations
TAMURA NoriyoshiBeppu University
MIZUNO ShojiThe University of Shiga Prefecture
SATO DaisukeTohoku University
WATANABE KoichiNational Institute of Japanese Literature
YASUE KohShinshu University
ABE OsamuNagoya University
YOSHIMURA KeiThe University of Tokyo

Background and objectives

If global warming causes many societal difficulties, how can we adapt to the change? Remarkable recent progress in palaeoclimatology has elucidated the fact that large climate variations often underlay epochs of human history. How did our ancestors address such change in the past? Human history must include many examples from which we can extract common lessons relevant to contemporary global environmental change. The research target of this project is Japanese history from the prehistorical Jomon era to the present. First, we reconstruct past climate variations in Japan and Asia at annual time resolutions for the last several millennia, using up-to-date palaeoclimatological methods to identify outstanding periods of climate variation. Then we use historical and archaeological approaches to investigate how local societies reacted to climate variation in order to clarify common sociocultural characteristics of societies that are tolerant or vulnerable to changes in climate.

Research methods

In this project, past climate variations are reconstructed based on various proxies, such as tree rings (Photo 1), historical weather records, lake and marine sediments, coral rings and speleothem, and compared with human responses recorded in historical documents (Photo 2) and archaeological archives. There are three reasons why we have chosen Japan as the main research area in this project. First, Japan is located at northeastern rim of the Asian summer monsoon, where small changes in monsoon dynamics might have significantly affected rice paddy cultivation on which Japanese sustenance has historically depended. Second, due to the historically high literacy rate and long-lasting family system in Japan, innumerable historical documents dating back to the 8th century are preserved in both private and governmental sectors. Third, rapid land developments during last several decades have allowed for precise archaeological excavations at numerous sites all over Japan. In addition, a palaeoclimatological tool (tree-ring cellulose oxygen isotope ratio) particularly useful in the Asian monsoon region has recently been developed to reconstruct summer precipitation on which rice paddy cultivation in Japan depends, providing archaeologists with a reliable tool for annual dating of numerous excavated woods (Photo 3).

Photo 1 Sampling of a tree ring core from a living tree using an increment borer

Photo 1 Sampling of a tree ring core from a living tree using an increment borer

Photo 2 Collection of historical information by investigation of old documents

Photo 2 Collection of historical information by investigation of old documents

Photo 3 Extraction of tree ring cellulose from archaeologically excavated wood

Photo 3 Extraction of tree ring cellulose from archaeologically excavated wood

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Remarkable results

We have used many tree-ring samples from around Japan in order to analyze tree-ring oxygen isotope ratios during the last 4800 years in annual time resolution. We have also collected many tree-ring width datasets from all over Asia in the framework of an international palaeo-climatological project (PAGES) and reconstructed inter-annual variations of averaged East Asia summer temperatures. Comparison of annual climate records and paleographic information such as yearly tax accounts in early modern villages and administrative documents on water control in medieval manors, archaeological evidence on prehistorical and ancient societies excavated from farmland and habitat remains, and the newest isotopic dendrochronological data (Fig. 1) allows us to investigate how variations in temperature or precipitation influenced agricultural production, human livelihoods, and water management. As a result, we can understand how historical societies could or could not overcome serious climate changes in the past. For example, in the Medieval period, sudden decreases in summer temperature often caused serious famines in Japan, though there were important exceptions during late 13th and 14th centuries (Fig. 2). On the other hand, sudden increases in precipitation often caused water disasters and subsequent social conflicts, analysis partly infered from the number of old documents relevant to emergence of “Akuto” (outlaws) in the Kamakura era (Fig. 3). Such relationships between precipitation, disaster and societal change can be traced back to the early period of the Yayoi era about 2500 years ago.

Figure 1

Figure 1 Numerous wooden posts along an ancient waterway excavated from Shoji remain in Neyagawa city, Osaka prefecture (a) and variations in their tree-ring cellulose oxygen isotope ratios (b). Coincidence of the variations among many posts indicates that this waterway was constructed in 227AD. Samples of wooden posts were provided by Neyagawa city board of education.

Figure 2

Figure 2 Variations in East Asia summer temperature (red: reconstructed from tree ring width database in Asian wide region) and famine reports in Japan (green: number of old documents from each year containing famine-words) during Medieval period.

Figure 3

Figure 3 Variations in Central Japan summer precipitation (blue: inferable from tree-ring oxygen isotope ratio) and documents related to “Akuto” (outlaws) (red: yearly ratios in all paleography) during the Kamakura era, 1185-1333 AD. Thick lines indicate five-year averages.

Final goal

As our present concerns for global warming clearly illustrate, large climate variations in the past have had serious impacts on our ancestors. As shown in Figs. 2 and 3, significant multi-decadal climate variations had especially negative impacts on historical societies. However, some past societies continued to attempt to overcome the influence of climate variations, while other societies collapsed. Comparative evaluation of historical climate adaptations may allow us to explain Japanese history since the Jomon era as a sequence of societal transformations designed to overcome large-scale intermittent climate variation. The final goal of this project is to bring such historical analysis to bear on fundamental adaptation strategies considered in relation to contemporary global environmental problems.

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