Climate change and large-scale human population collapses in the pre-industrial era

Abstract

Aim It has long been assumed that deteriorating climate (cooling and warming above the norm) could shrink the carrying capacity of agrarian lands,depriving the human population of sufficient food.Population collapses (i.e.negative population growth) follow. However, this human‐ecological relationship has rarely been verified scientifically, and evidence of warming-caused disaster has never been found. This research sought to explore quantitatively the temporal pattern, spatial pattern and triggers of population collapses in relation to climate change at the global scale over 1100 years. Location Various countries/regions in the Northern Hemisphere (NH) during the pre-industrial era. Methods We performed time-series analysis to examine the association between temperature change and country-wide/region-wide population collapses in different climatic zones.All of the known population collapse incidents in the NH in the period ce 800‐1900 were included in our data analysis. Results Nearly 90% of population collapses in various NH countries/regions occurred during periods of climate deterioration characterized by shrinking carrying capacity of the land.In addition,we found that cooling dampened the human ecosystem and brought about 80% of the collapses in warmer humid,cooler humid and dry zones, while warming adversely affected the ecosystems in dry and tropical humid zones. All of the population collapses and growth declines in periods of warm climate occurred in dry and tropical humid zones. Malthusian checks (famines, wars and epidemics) were the dominant triggers of population collapses, which peaked dramatically when climate deteriorated.