Scientific Method / Science & Exploration

European wars, famine, and plagues driven by changing climates

Social disturbances in preindustrial Europe have been ascribed to a variety of …

The Thirty Years War was especially deadly.

Economic chaos, famine, disease, and war may all be attributed to climate change, according to a recent study. Through advances in paleoclimatology, researchers used temperature data and climate-driven economic variables to simulate the climate that prevailed during golden and dark ages in Europe and the Northern Hemisphere from 1500-1800 AD. In doing so, they discovered a set of casual linkages between climate change and human crisis. They noted that social disturbance, societal collapse and population collapse often coincided with significant climate change in America, the Middle East, China, and many other countries in preindustrial times, suggesting that climate change was the ultimate cause of human crisis in many preindustrial societies.

The General Crisis of the 17th Century in Europe was marked by widespread economic distress, social unrest, and population decline. A significant cause of mankind’s woes during these times was the climate-induced shrinkage of agricultural production. Bioproductivity, agricultural production, and food supply per capita all showed immediate responses to changes in temperature. In the five to 30 years following these changes, there were also responses in terms of social disturbance, war, migration, nutritional status, epidemics, and famine.

Cooling during the Cold Phase (1560-1660 AD) reduced crop yields by shortening the growing season and shrinking the cultivated land area. Although agricultural production decreased or became stagnant in a cold climate, population size still grew, leading to an increase in grain price and an increased demand on food supplies. Inflating grain prices led to hardships for many, and triggered social problems and conflicts such as rebellions, revolutions, and political reforms. 

Many of these disturbances led to armed conflicts, and the number of wars increased 41 percent during the Cold Phase. During the latter portion of the Cold Phase, the number of wars decreased, but the wars lasted longer and were far more lethal—most notable was the Thirty Years War (1618-1648), where fatalities were more than 12 times of the conflicts between 1500-1619.

Famine became more frequent too. Nutrition deteriorated, and the average height of Europeans shrunk 2cm by the late 16th century. As temperatures began to rise again after 1650, so did the average height. 

The economic chaos, famine, and war led people to emigrate, and Europe saw peak migration overlapping the time of peak social disturbance. This widespread migration, in conjunction with declining health caused by poor nutrition, facilitated the spread of epidemics, and the number of plagues peaked during 1550-1670, reaching the highest level during the study period. As a result of war fatalities and famine, the annual population growth rate dropped dramatically, eventually leading to population collapse.

In the 18th century, the mild climate improved matters considerably, leading to the speedy recovery of both Europe’s economy and population.

The alternation between periods of harmony and crisis, golden ages and dark ages, closely followed variations in the food supply per capita. Consequently, grain price could be used as an indicator of crisis in preindustrial Europe. Although grain price is dictated by agricultural production and population size, analysis by the researchers shows that temperature change was the real cause behind the grain price, since agricultural production was climate-dependent at the time.

The history of golden and dark ages in Europe is often attributed to sociopolitical factors, which fails to explain the co-occurrence of long-term crises in different countries, at different stages of development, and across different climate zones. Instead, the authors make a compelling case that climate change is the culprit, thanks to a climate-driven economic downturn due to a decreasing food supply. Where there is a shrinking food supply, chaos and misery follow.

PNAS, 2011, DOI: 10.1073/pnas.1104268108

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