Climate and environment in historyRegionally, it is possible to identify variations in society and culture that are clearly rooted in
environmental differences. For example, the extent of colonization by immigrant farmers during
the Yayoi period was essentially determined by environmental conditions. In the north, Tōhoku
and Hokkaido were too cold for rice farming given the technology of the time, while in the
south, southern Kyushu and the Ryukyu chain were unsuitable in terms of soil and topography.
As a result, the archipelago became split into a central, agricultural zone encompassing most of
Honshu, Shikoku, and Kyushu, and peripheral zones occupied by foragers to the north and
south.^32 Although there was a tendency for the central zone to expand at the expense of the
peripheral zones over time, the tripartite structure itself survived until the nineteenth century.
Societies in the three zones followed separate historical trajectories, and at any given time dif-
fered profoundly in most aspects of human life, both material and non- material. In a very real
sense, these differences had environmental causes.^33
Before leaving this topic I should also note none of the three large zones was monolithic; each
can be further divided on the basis of local variations in culture, broadly defined. One example
beloved of cultural anthropologists and other scholars is the long- standing split between east and
west in the central zone.^34 The observed divergences in customs and social structure are generally
ascribed to underlying ecological differences, including the greater suitability of the west for
wet- rice farming and of the east for dry- field cultivation. More study, however, is certainly
required.
In all of the above examples, seemingly unchanging environmental conditions are used to
explain, or at least illuminate, characteristics of Japanese society. But, as we have seen, environ-
mental conditions actually change over time, the best example being climate. How have chang-
ing climatic conditions influenced the course of history in the Japanese islands?
Perhaps the most that can be said at this point is that there are some very interesting corre-
spondences. The first and most obvious is the close fit between climate change at the end of the
last Ice Age and the emergence of the Jōmon culture of sedentary foragers. Although it was pre-
viously thought that origins of pottery (and thus, by definition, the Jōmon culture) postdated the
end of the Ice Age, pottery is now thought to have emerged earlier, in the context of extreme
climatic fluctuations.^35 In either case, the temporal association between climate change and cul-
tural change seems too close to result from chance. Regarding the Jōmon period itself, there
seems to be an association between climatic warming and later cooling, on the one hand, and
population growth and then decline, on the other.^36 Moving forward in time, one is struck by the
spread of agriculture and growth in political organization during the cold Yayoi and Kofun
periods, when natural food resources would have been unreliable and social cohesion was needed
to overcome the challenges posed by nature.^37 In the historical period, perhaps the most striking
correlation is that between rapid climatic oscillations and political unrest in the medieval centu-
ries.^38 (Another, counterintuitive, one is between the onset of the Little Ice Age in the seven-
teenth century and the robust demographic and economic growth that marked the same
period.)
Recently, paleoclimatologist Nakatsuka Takeshi has contributed to this debate by comparing
climatic fluctuations (specifically, changes in precipitation as recorded in tree rings) with the
archaeological and the historical records. To make a long story short, Nakatsuka finds that
periods of political instability in the Japanese islands—not only the medieval period, but also the
second century ce, when the Chinese Wei History records widespread warfare in Japan—tend to
coincide with relatively short- term (decadal) fluctuations in precipitation. Nakatsuka argues that
human societies can adapt to either wet or dry conditions, as well as to long- term shifts from one
to the other, which are essentially invisible on the scale of a human life. What they cannot easily
adapt to is rapid, unforeseen change.^39