Changes in climate and secular population cycles in China, 1000 CE to 1911

Abstract

Many studies of secular population cycles in historical China conclude that when population is large -relative to the land's carrying capacity -further population increase can lead to mortality crises through war, famine and epidemics, resulting in subsequent population decline. In these studies, population cycles are thought to be driven primarily by population growth. Nevertheless, some scholars have noted a strong correlation between deteriorating climate, dynastic change, and population collapse in historical China. They suggest climate forcing as the underlying driver of population cycles, but quantitative evidence has been lacking to date. In the present study, we employed high resolution temperature data, reports on mortality events, and population datasets to quantitatively examine the extent to which climate change was responsible for Chinese population cycles. Results show that there were 5 major population contractions in China between 1000 CE and 1911, and all of them occurred in periods with a cold climate, when mortality crises triggered population collapses. Nevertheless, the climate-population association is non-linear, because it is mediated by population pressure. Although social buffers were increasingly effective in dissipating climate forcing, they could not prevent population collapses from occurring during periods of long-term cooling. Our results challenge classic Malthusian and post-Malthusian interpretations of historical Chinese population cycles.

The causality analysis of climate change and large-scale human crisis

“…More recent breakthroughs came from research adopting quantitative approaches to all known cases of social crisis. These studies show that, in recent history, climate change was responsible for the outbreak of war, dynastic transition, and population decline in China, Europe, and around the world because of climate-induced shrinkage of agricultural production (6)(7)(8)(9)(10)(11)(12)(13)(14)(15). However, the underlying causal linkages from climate change to agricultural production and various human catastrophes in history have not been addressed scientifically.…”

A tale of two population crises in recent Chinese history

“…In China in the past millennium, the clustering of natural calamities and human catastrophes in times of cold climate was found not only in one or two cold phases, but in all of the cold phases (Lee and Zhang 2010). And in a cold climate, many things went wrong not only in China, but also in many parts of the world where the population system had already pushed against its Malthusian constraints (Zhang et al 2011;Zhang et al 2007a).…”

“…were depleted, the accumulated population pressure was unleashed via internecine warfare, resulting in population collapses (Lee and Zhang 2010). In fact, the above scenario, brought by population growth and climate change, is entirely beyond the managing capacity of any emperor/government within the context of historical agrarian China.…”

“…(1) The linkage between temperature change and population growth shows up through fluctuations in agricultural production (Lee et al 2008;Lee and Zhang 2010;Lee et al 2009). Cooling shortens the crop growing season and reduces farmland area (Galloway 1986).…”

“…Recent studies, however, suggest that climate change resulted in human catastrophes only if the population system had already pushed against its Malthusian constraints (Stenseth and Voje 2009;Turchin and Nefedov 2009). In our latest empirical study (Lee and Zhang 2010), although climate change is shown to be an important factor in driving historical Chinese population cycles, 2 the climate-population relationship is, in fact, mediated by population growth. Briefly, the above literature suggests that the mechanism may not be population growth or climate change alone, but the two factors working synergistically to drive population cycles in historical China.…”