Climatic signatures in crops and grain prices in 19th-century Sweden

Climate and weather variation affect agricultural productivity, with consequences for both overall food availability and the wider economy. Knowledge of these processes has implications for understanding historical demography and predicting effects of climate change on societies. We studied the relationships between ambient temperature and the yields and prices of principle grains (wheat, rye, barley oats) in Sweden from 1803 to 1914. We found that the annual general crop index (a measure of overall crop yield) correlated negatively with the annual average price of the four grains. Overall temperature during the period of crop growth was related positively to general crop index and negatively to average crop price. At the level of month of crop growth, when the relationship between temperature and general crop index was most positive, that between temperature and average crop price was most negative. This strong structured relationship was found to be consistent when yields of each crop were considered separately, and indicates that the relationships between crop yield and crop price were to a large extent due to the influence of ambient temperature. Price correlations between pairs of crop species were in all cases greater than the correlation of yields. Within individual crops, correlations between price and yield were stronger for those crops for which imports were not available, and which were therefore subject to the weakest influence from rising globalisation. Our analyses demonstrate the sensitivity of historical agriculture to climatic factors, and the extent to which this affected the wider economy. It is likely that the susceptibility of agriculture to climatic risks was ascended by the concomitant climate regime, the ‘Little Ice Age’. Moreover, our study period spans the period of rising globalisation, and suggests a weakening influence of prevailing weather on crop prices.