Scholars are divided regarding the assertion that prolonged dry periods may have precipitated conflicts in late Roman Britain. While climate scientists have identified climatic evidence of drought aligning with periods of unrest and military engagements, historians contend that this evidence stems from a misinterpretation of pivotal written records.
This disagreement underscores the persistent challenges researchers encounter when endeavoring to reconcile past climatic data with historical accounts. “This situation arises repeatedly,” observes Dagomar Degroot, a climate historian at Georgetown University in Washington D.C. He notes that such discrepancies highlight the complexities of interdisciplinary research.
Tree Ring Data Links Drought to British Unrest
A study published in the previous year, led by geographer Ulf Büntgen of the University of Cambridge, employed tree ring analysis from oak specimens in southern Britain and northern France. This investigation aimed to reconstruct climatic patterns between AD 288 and 2009.
The research team pinpointed a series of intense summer droughts in southern Britain occurring between AD 364 and 366. They proposed a connection between these drought conditions and the period known as the “Barbarian Conspiracy” in 367. During this time, warriors originating from Britain and Ireland achieved several victories against the Roman Empire, even capturing a high-ranking commander. Although Roman authority was eventually re-established, the empire gradually withdrew from Britain over the subsequent fifty years.
Büntgen and his colleagues hypothesized that the severe drought led to crop failures, thereby inciting local leaders to revolt against Roman rule. Their findings were not confined to Britain; the study extended its analysis to the broader Roman Empire. By examining a compilation of 106 recorded battles in conjunction with European tree ring data, they discovered a correlation: battles were more probable in the years immediately following dry summers and exceptionally hot periods.
These findings garnered significant media attention, being reported by prominent outlets such as the BBC, The Guardian, and The Telegraph.
Historians Challenge the Interpretation of Historical Sources
However, a counter-argument has since emerged from another research group, published in the same journal, Climatic Change. Helen Foxhall Forbes, a historian at Ca’ Foscari University of Venice in Italy, stated, “We believed there were too many issues with the paper to let it pass unchallenged.”
Forbes acknowledges the compelling nature of the past climate data but asserts that the study’s interpretations of historical and archaeological texts are frequently inaccurate. She points to Ammianus Marcellinus, a Roman author who lived between approximately 330 and 400 AD, as the sole extant source concerning the Barbarian Conspiracy. Marcellinus wrote a history of Rome, the Res gestae, decades after the events, with only fragments surviving.
James Harland, a historian from the University of Bonn in Germany, describes sections of Marcellinus’s text pertaining to the Barbarian Conspiracy as both “fragmentary” and bordering on “gibberish.” The precise meaning of “barbarica conspiratio” remains ambiguous; while a coordinated revolt is a plausible interpretation, it could equally signify raiding, social unrest, or other forms of disturbance.
Similarly, Marcellinus describes the state of the Britons as “ultimam… inopiam.” This phrase approximates to “utter helplessness,” which may refer to a famine or something entirely different. Crucially, Marcellinus presents this state of inopiam as a result of the barbarica conspiratio, not its antecedent. “They absolutely cannot argue that drought caused a famine, which, in turn, caused a barbarian conspiracy, if they are relying on what Ammianus says, because that isn’t what he says,” Foxhall Forbes elaborated.
Debate Over Causality and Data Interpretation
In response, Büntgen and his team have published their rejoinder, also in Climatic Change. They reference a 1984 academic paper that interprets “inopiam” as signifying “famine.” However, Foxhall Forbes and her colleagues highlight a more recent, comprehensive re-evaluation from 2009. This later analysis critically examined the language and historical context employed by Ammianus Marcellinus.
Adding another layer of complexity, Dan Lawrence, an archaeologist at Durham University in the UK, points out the heterogeneity of the conflicts included in the battle database. Some entries describe direct confrontations, while others appear to represent urban disturbances. He suggests that while a food shortage resulting from drought could conceivably lead to riots if mishandled, and potentially escalate into wider conflict, such causal pathways require explicit demonstration. “They did not have a historian on their team who could have informed them about some of this information,” Foxhall Forbes remarked, noting that while two authors are archaeologists, neither specializes in late Roman Britain.
Büntgen defends his team’s multidisciplinary approach, stating that archaeologists specializing in the Roman Empire were indeed part of the project. He expressed a desire for a “constructive debate” where other researchers could re-examine or supplement the existing data, building upon their work. Büntgen also noted that many studies examining climate and history, including his own, often overlook ecologists. These individuals are vital for understanding how climatic anomalies impact agricultural systems. “That is where most of the studies are very vague,” he conceded.
Degroot, who was not involved in the critical response, described the absence of dedicated historical expertise as a “real weakness” of the study. Nevertheless, he considers the core of the research—the tree ring data—to be valuable for historical inquiry. “We still do see, now, that droughts probably did happen,” he stated. The ongoing challenge, he suggests, is to clarify through specific case studies whether drought actually influenced instances of violence.
Interpreting Historical Narratives
Degroot also spoke about the inherent tension in historical interpretation, contrasting “minimalist” and “maximalist” approaches. Minimalists tend to focus on granular details of specific events and are disinclined to generalize, making it difficult for them to construct broader narratives. “They are better at stating what did not happen than what did happen,” Degroot observed. “That is not very interesting.” Conversely, maximalists attempt to identify overarching patterns within incomplete datasets. “They can construct these truly impressive narratives, sometimes identifying forces that have not been considered before,” he said, though he cautioned that such ideas can sometimes prove to be “built on sand.”