|KAMATANI Kaoru||RIHN Senior Project Researcher|
|Project Researchers at RIHN|
|ITO Keisuke||Project Researcher|
|TSUSHIMA Akane||Project Researcher|
|LI Zhen||Project Researcher|
|TESHIMA Mika||Project Research Associate|
|Main Project Members|
|SANO Masaki||Waseda University|
|WAKABAYASHI Kunihiko||Doshisha University|
|HIGAMI Noboru||Aichi Prefectural Center for Archaeological Operations|
|TAMURA Noriyoshi||Beppu University|
|MIZUNO Shoji||The University of Shiga Prefecture|
|SATO Daisuke||Tohoku University|
|WATANABE Koichi||National Institute of Japanese Literature|
|YASUE Koh||Shinshu University|
|ABE Osamu||Nagoya University|
|YOSHIMURA Kei||The University of Tokyo|
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 or seasonal 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.
In this project, past climate variations are reconstructed based on various proxies, such as tree rings (Photo 1, 3), 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weather records, lake and marine sediments, coral rings and speleothem, and compared with human responses recorded in historical documents (Photo 2) and archaeological archives.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 Second, due to the historically high literacy rate and long-lasting family system in Japan, innumerable historical documents dating back to the 8th century are preserved in both private and governmental sectors.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 (Fig. 1).
Figure 1 A thin wood plate (a) and its chemical treatment residue (cellulose) (b) from a pile wood at a rice paddy field in the Yayoi era. Variation in the tree-ring cellulose oxygen isotope ratio is compared with that in master chronology to determine the matching year (c & d).
So far, we have been using many tree-ring samples from around Japan in order to analyze tree-ring oxygen isotope ratios during the last 4300 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 summer temperature in East Asia. Comparison of annual records of past climate with paleographic information such as yearly tax accounts in early modern villages and administrative documents on water control in medieval manors, as well as archaeological information on prehistorical and ancient societies excavated from farmland and habitat remains, coupled with the newest isotopic dendrochronological data allow 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. In the Edo era, summer temperature changed cyclically with about 40 years of periodicity and sudden temperature decreases often reduced rice yield drastically and caused serious famines in Northeast district of Japan (Fig. 2). In the medieval period, we find tight relationships between temperature and famine as well, but also that sudden increases in precipitation often caused water disasters and subsequent social conflicts and warfare (Fig. 3). Such relationships can be traced back to the early period of the Yayoi era about 2500 years ago.
As our present concerns for global warming clearly illustrate, large climate variations in the past have always had serious impacts on our ancestors. As shown in Figs. 2 and 3, multi-decadal large climate variations had especially damaged historical societies. However, some past societies continued making efforts 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 intermittent climate variations. The final goal of this project is to bring such historical insight into consideration of fundamental adaptation strategies in relation to contemporary global environmental problems.▲PAGE TOP