As long-living lifeforms, trees can provide scientists with a way to look back into the past, revealing everything from a reversal in Earth's magnetic field 42,000 years ago to a time in 774 CE when the planet was bombarded by a massive radiation storm. Now, researchers have used tree-ring data to determine that a massive drought could have spurred incursions by Hunnic hordes into the eastern Roman Empire in the 430-450s CE, events that eventually led to the realm's collapse.
University of Cambridge researcher Ulf Büntgen and his colleagues analyzed tree rings to reconstruct climate data from the last 2,000 years. They came to the conclusion that present-day Hungary, then one of the borders of the Roman Empire, experienced unusually dry summers in the 4th and 5th centuries, with full-on droughts between 420 and 450 CE.
This is a time period that falls within the span of mass migration during what's commonly known as the Barbarian Invasions between 300 to 700 CE. It's well known that the Huns violently attacked the lands claimed by Rome during this time, but the thirst for gold and territory is typically cited as a major motivating factor.
The Cambridge research points at another possible reason: hunger.
The drought that hit the region during this time would have led to crop failures and diminished grazing lands, and sent tribes away from their homes to seek food in other regions.
"If resource scarcity became too extreme, settled populations may have been forced to move, diversify their subsistence practices and switch between farming and mobile animal herding," said Assoc. Prof. Susanne Hakenbeck from Cambridge's Department of Archaeology, who is co-author on the study. "These could have been important insurance strategies during a climatic downturn."
Indeed, analysis of skeletons from five cemeteries in the region by Hakenbeck and her colleagues showed that many individuals changed their diets significantly over their lifetimes, switching regularly from farming to herding.
While the team acknowledge that more research needs to be conducted to confirm their theory that drought was a major motivator for raids by the Huns, they do point to a demand made by Attila after attacks on the Roman enclaves of Thrace and Illyricum. He asked for a strip of land "five days journey wide" along the Danube, which, the researchers say could be evidence that the Huns needed such land to provide better grazing for their livestock during a drought.
"Climate alters what environments can provide and this can lead people to make decisions that affect their economy, and their social and political organization," said Hakenbeck. "Such decisions are not straightforwardly rational, nor are their consequences necessarily successful in the long term. This example from history shows that people respond to climate stress in complex and unpredictable ways, and that short-term solutions can have negative consequences in the long term."
Coincidentally, Hungary has just come through its worst drought since meteorological data has been recorded, causing severe crop failures. According to Dutch agricultural portal Agroberichten Buitenland, "300,000 hectares (about 74,1316 acres) of maize and 200,000 hectares (about 494,210 acres) of sunflower crops have been completely destroyed. The damage to agriculture is estimated to be over €1 billion."
The researchers' work has been published in the Journal of Roman Archaeology.
Source: University of Cambridge
