Solar radiation, rice prices, and migration in northeastern Japan during the 18th and 19th centuries

This study explores the impact of variations in solar radiation on historical migration patterns through economic stress, such as severe famines, crop failures, and rice price fluctuations. Using individual-level panel data from annual population registers (Ninbetsu-Aratame-Cho) covering the years 1708 to 1870 CE for three agricultural villages and one commercially active town in central Fukushima, northeastern Japan, we analyzed demographic indicators – total migration, legal migration, absconding, and mortality – recorded in the registers in relation to crop failures, rice prices, and reconstructed solar radiation. Monthly solar radiation reconstructed from historical weather records indicated significant reductions during the severe famines of the 1780s and the 1830s, periods associated with increased migration and absconding. A detailed analysis of the Tenpō famine (1833−1838) demonstrated clear correlations between reduced solar radiation and subsequent sharp increases in rice prices, elevated mortality rates in subsequent years, and, with a lag of approximately two years, increased absconding. This study highlights the importance of integrating solar radiation into migration research, further advancing our understanding of the historical linkages between climate variation and human mobility.