One of the great mysteries of late medieval history is why the Norse, who had successfully established colonies in southern Greenland in 985, abandoned them in the early 15and century? The consensus has long been that colder temperatures, coupled with the Little Ice Age, helped make the settlements unsustainable. However, new research, conducted by the University of Massachusetts at Amherst and recently published in Scientists progress, reverses this old theory. It was not the drop in temperatures that helped drive the Scandinavians out of Greenland, but the drought.
When the Norse settled in Greenland on what they called the Eastern Colony in 985, they prospered by clearing the land of shrubs and planting grass as pasture for their cattle. The Eastern Colony’s population peaked at around 2,000, but collapsed quite rapidly around 400 years later. For decades, anthropologists, historians and scientists have believed that the demise of the Eastern Settlement was due to the onset of the Little Ice Age, a period of unusually cold weather, particularly in the North Atlantic, which made agricultural life in Greenland untenable.
However, as Raymond Bradley, University Professor Emeritus of Geosciences at UMass Amherst and one of the paper’s co-authors points out, “Prior to this study, there was no data on the actual site of Viking settlements. . And that’s a problem.” Instead, the ice core data that previous studies had used to reconstruct historic temperatures in Greenland was taken from a location more than 1,000 kilometers to the north and more than 2,000 meters above sea level. ‘altitude. “We wanted to study how the climate had varied near the northern farms themselves,” says Bradley. And when they did, the results were startling.
Bradley and his colleagues traveled to a lake called Lake 578, which is adjacent to an old Norse farmhouse and near one of the largest clusters of farms in the Eastern Colony. There, they spent three years collecting sediment samples from the lake, which was a continuous record for the past 2,000 years. “No one has actually studied this place before,” says Boyang Zhao, the lead author of the study who conducted this research for his doctorate. in Geosciences at UMass Amherst and is currently a Postdoctoral Research Associate at Brown University.
They then analyzed this 2,000-year-old sample for two different markers: The first, a lipid, known as BrGDGT, can be used to reconstruct temperature. “If you have a sufficiently comprehensive record, you can directly link changing lipid structures to temperature changes,” says Isla Castañeda, a geoscience professor at UMass Amherst and one of the paper’s co-authors. A second marker, derived from the waxy coating on plant leaves, can be used to determine the rates at which grasses and other livestock-feeding plants lose water due to evaporation. It is therefore an indicator of the degree of drought.
“What we found,” Zhao says, “is that while the temperature barely changed during the Norse settlement of southern Greenland, it got drier and drier over time.”
Norse farmers had to overwinter their livestock on stored fodder, and even in good years the animals were often so weak that they had to be transported to the fields once the snow had finally melted in the spring. Under such conditions, the consequences of the drought would have been serious. A prolonged drought, in addition to other economic and social pressures, may have tipped the balance just enough to make the Eastern Colony unsustainable.
Scientists from Smith College and the University at Buffalo also contributed research, which was supported by the National Science Foundation, UMass Amherst, the Geological Society of America and the Swiss National Science Foundation, is changing our understanding of the ancient European history and highlights the importance of continuing to explore how environmental factors influence human society.