How a Drought Sparked Chaos in Roman Britain!
A new study from the University of Cambridge has uncovered how a severe three-year drought helped spark one of the most dramatic uprisings in Roman Britain – the so-called “Barbarian Conspiracy” of 367 CE. The research reveals that extreme weather, combined with political fragility and military strain, left the province open to devastating attacks by the Picts, Scotti, and Saxons.
Using tree-ring data from oak trees in southern Britain and northern France, scientists were able to reconstruct summer climate conditions from the 4th to 6th centuries. Their findings, published in Climatic Change, show that the summers of 364, 365, and 366 CE were exceptionally dry – far too dry to grow staple crops like barley and spelt wheat. While the average summer rainfall needed during the growing season was around 51mm per month, these years saw a steep drop to just 28–37mm.
Photo Credit: Norman et al., Climatic Change (2025)
Professor Ulf Büntgen from Cambridge’s Department of Geography explained, “Three back-to-back droughts would have had a disastrous impact on Roman Britain's key farming regions. Ancient sources suggest this caused widespread food shortages, which in turn led to deep social unrest.”
By 367 CE, the shortages had turned into full-blown famine. The Roman historian Ammianus Marcellinus wrote that the population was suffering under the “utmost conditions of famine.” The Roman army, already stretched thin, began to fall apart – with troops abandoning their posts along Hadrian’s Wall. With the military weakened, Britain was ripe for invasion.
Photo Credit: Norman et al., Climatic Change (2025)
And invade they did. The Picts stormed in from the north, the Scotti raided from Ireland to the west, and the Saxons launched attacks from the south. Roman commanders were either captured or killed, and in some cases, Roman soldiers even switched sides. Though Emperor Valentinian I eventually regained control in 369 CE, the damage was done. The Roman hold on Britain was never the same, and by around 410 CE, the empire had pulled out entirely.
The study also offers insight into why this major uprising occurred. While historians have long written about the “Barbarian Conspiracy,” archaeological evidence explaining its cause had been scarce. Lead author Charles Norman, a PhD student at Cambridge, said their work helps pinpoint the environmental trigger behind the crisis.
Beyond its historical significance, the study carries a clear message for the present day. Co-author Tatiana Bebchuk noted that the ancient link between climate and conflict has echoes in our own world. “We’re seeing more clearly now how extreme weather can lead to food shortages, which can then drive social and political instability.”
This research is a stark reminder that even the most powerful civilisations can falter when nature turns against them.