Quantitative Analysis of Climate Change and Human Crises in History - Space-Time Integration in Geography and GIScience - page 252

during AD 1580-1650, overlapping exactly with the peak of social disturbance.
This correlation indicates that social conditions are imperative in driving migration
(Wrigley and Schofield 1981 ). Migration, coupled with individuals' deteriorating
health caused by poor nutrition, facilitated the spread of epidemics (Zhang et al.
2007a ). The number of plagues peaked during AD 1550-1670 (Fig. 14.6 f, black
line), reaching the highest level throughout the study period (i.e., AD 1500-1800).
Population growth rate, which is codetermined by famine, epidemics, and war,
fluctuated in a complex manner. When peaks in war fatalities and famine occurred
during AD 1620-1650, the annual population growth rate (Fig. 14.1 h, black line)
dropped dramatically from 0.4 to 0.3 %. Population collapse occurred (Fig. 14.1 h,
red line), and the European population dropped to its lowest point (105 million
people) in AD 1650.
In general, variables in European societies (except population) reacted linearly
to temperature change at the multi-decadal time scale (Fig. 14.6 ). Some variables,
however, responded exponentially to cooling in AD 1620-1650. We further exam-
ined the time-series of those variables and found that, after cooling, population
pressure rose after AD 1560 (the agricultural production index declined, and annual
population growth was 0.4 %) to the point that a significant reduction of population
size was necessary to ease food strain in Europe. The triggers of population collapse
were war and famine. After AD 1618, many large-scale wars and famines occurred
in Europe. The war fatality index was 20 times higher than the AD 1500-1617
average and persisted at a similar level for the next 32 years (Fig. 14.6 g, red line).
During AD 1618-1649, 10 million people perished in wars (Brecke 1999 ).
Humans have served as both producers and consumers in Earth's ecosystem
since the Agricultural Revolution. During great wars and famines, death rates
exceeded birth rates, causing substantial reduction of the agricultural production
workforce. Also, collapse of agricultural production infrastructure caused by wars
left behind massive damage to carrying capacity and sustainability (Zhang et al.
2006 ). Consequently the role of the human population as a producer became less
significant. Although the temperature and grain yield in AD 1600-1620 and 1620-
1650 were similar, in AD 1621 the feedback effect of population collapse brought
about a 13 % reduction in agricultural production, which had stagnated for 50 years.
Such a huge decrease caused an exponential increase in grain price ( C 200 %),
famine ( C 250 %), war fatality ( C 1,350 %), social disturbance ( C 100 %), migration
( C 250 %), and other population checks. On the other hand, real wages, body
height, and epidemics remained at the same level, and the number of wars dropped
slightly (Fig. 14.6 ). This complex relationship between agricultural production and
population size continued until AD 1650, when temperature and thus agricultural
production increased.
At the end of the Cold Phase there was an augmentation of agricultural
production that, together with a population slump, led to a rise in FSPC and the
recuperation of most of European society after AD 1660. This date marks the end
of the General Crisis of the Seventeenth Century and the start of the Enlightenment
era. The mild climate in the eighteenth century created human ecological harmony,
leading to a speedy economic and population recovery in Europe. Although the short