The physics of large-scale food crises

TL;DR

This paper explores common features of large-scale food crises, revealing a power law relationship between death surges and birth declines, and proposes using birth data as an early warning indicator for such crises.

Contribution

It identifies a universal power law relationship between death spikes and birth declines during food crises and introduces a method to detect crises using birth data when death data are unreliable.

Findings

Power law relationship between death spikes and birth declines.

Birth reduction can serve as an early warning signal.

Method applicable when death data are uncertain or missing.

Abstract

Investigating the ``physics'' of food crises consists in identifying features which are common to all large-scale food crises. One element which stands out is the fact that during a food crisis there is not only a surge in deaths but also a correlative temporary decline in conceptions and subsequent births. As a matter of fact, birth reduction may even start several months before the death surge and can therefore serve as an early warning signal of an impending crisis. This scenario is studied in three cases of large-scale food crises. Finland (1868), India (1867--1907), China (1960--1961). It turns out that between the regional amplitudes of death spikes and birth troughs there is a power law relationship. This confirms what was already observed for the epidemic of 1918 in the United States (Richmond et al. 2018b). In a second part of the paper we explain how this relationship can be used for the investigation of mass-mortality episodes in cases where direct death data are either uncertain or nonexistent.