At a Glance
- A new study reveals that severe droughts between 364 and 366 CE significantly destabilized Roman Britain by reducing crop yields and causing food shortages.
- The resulting famine weakened the Roman military, setting the stage for the Barbarian Conspiracy of 367 CE when several tribes successfully invaded the vulnerable province.
- Climate reconstructions using oak tree-ring data showed arid summers directly contributing to grain failures, especially in southern Britain, where most food was produced.
- Researchers linked the timing of major battles across the Roman Empire to preceding dry years, showing how climate stress consistently led to increased conflict and instability.
- This research highlights how extreme weather events can undermine political and military systems, offering important lessons about the historical impact of climate on societal resilience.
Researchers have uncovered new evidence suggesting that climate change played a significant role in the downfall of Roman Britain during the 4th century. A study published in the journal Climate Change and led by the University of Cambridge has shown that severe droughts between 364 and 366 CE severely impacted crop production, leading to food shortages and social instability. These findings are based on tree-ring data and historical accounts, confirming that extreme weather conditions triggered a chain of events that weakened Roman defenses in Britain.
The study focuses on the “Barbarian Conspiracy” of 367 CE, a key moment in Roman Britain’s history when multiple tribes, including the Picts, Scotti, and Saxons, launched attacks on the province. The researchers suggest that the severe droughts contributed to a collapse in food supplies, leaving Roman soldiers unable to fulfill their duties. Historical sources, including the Roman historian Ammianus Marcellinus, describe Britain as being in a state of famine by this time, supporting the idea that the drought-driven grain shortages were a key factor in the rebellion and subsequent invasion.
The research team reconstructed the climate conditions during this period using oak tree-ring records, which allowed them to assess the amount of rainfall and temperature fluctuations. They found that the summers of 364, 365, and 366 CE were exceptionally dry, with rainfall significantly lower than usual. This drought caused major crop failures, particularly in southern Britain, where most of the province’s grain was grown. The lack of food and resources weakened Roman presence, allowing peripheral tribes to invade and raid Roman Britain.
This study offers new insights into the relationship between climate and conflict, with the researchers expanding their analysis to the entire Roman Empire. They found that many battles fought during this period were preceded by dry years, highlighting how climate-induced stress can lead to societal challenges. These findings change our understanding of Roman Britain’s collapse and emphasize the broader impact of extreme climate events on human societies throughout history.
References
- University of Cambridge. (2025, April 17). Extreme drought contributed to barbarian invasion of late Roman Britain, tree-ring study reveals. Phys.Org; University of Cambridge. https://phys.org/news/2025-04-extreme-drought-contributed-barbarian-invasion.html
- Norman, C., Schwinden, L., Krusic, P., Rzepecki, A., Bebchuk, T., & Büntgen, U. (2025). Droughts and conflicts during the late Roman period. Climatic Change, 178(5), 87. https://doi.org/10.1007/s10584-025-03925-4
