The absence of monsoon rains at the source of the Nile was the cause of migrations and the disappearance of entire settlements in the Roman province of Egypt. This demographic development was compared with environmental data for the first time by ancient history professor Sabine Huebner of the University of Basel - leading to a discovery of climate change and its consequences.

The oasis-like region of Faiyum, about 130 km southwest of Cairo, was the breadbasket of the Roman Empire. However, by the end of the third century C.E., several formerly prosperous settlements declined and were abandoned by their inhabitants. Earlier excavations and contemporary papyri showed that problems with field irrigation were the cause. Attempts by local farmers toadapt to drought and desertification of agricultural land-for example, by changing their farming practices-are also documented.

Volcanic eruption and monsoon rains

The Basel professor of ancient history, Sabine R. Huebner, showed in the American newspaper Studies in Late Antiquity that changing environmental conditions are behind this development. Existing climatic data indicate that monsoon rains in the headwaters of the Nile in the Ethiopian Highlands suddenly and permanently weakened. The result was a reduction in the summer water level of the river. Evidence to support this has been found in geological sediments from the Nile Delta, Faiyum andthe Ethiopian Highlands, which provide long-term climate data on monsoons and the water level of the Nile.

A powerful tropical volcanic eruption around 266 CE, which the following year brought a below-average Nile flood, presumably also played a role. Major eruptions are known for sulfuric acid deposits in Greenland and Antarctic ice cores, and can be dated back up to three years. Particles released into the stratosphere lead to cooling of the climate,disrupting the local monsoon system.

New insights on climate, environment and society

In the third century CE, the entire Roman Empire was hit by crises that are relatively well documented in the province of Egypt by more than 26,000 preserved papyri (documents written on papyrus leaves). In the Faiyum region, this includes records of inhabitants switching to growing vines instead of grain or raising sheep due to water shortages. Others chargedtheir neighbors from stealing water or appealed to the Roman authorities seeking tax reductions. These and other adaptive strategies of the population delayed the death of their villages for several decades.

"Like today, the consequences of [ancient] climate change were not the same everywhere," says Huebner. While regions on the edge of the desert faced the severity of drought, others actually benefited from the influx of people moving out of abandoned villages. "New knowledge about the interaction of climate, environmental change and social developments isThe climate changes of late antiquity was not, however, caused primarily by humans, but was based on natural fluctuations.