Although the first humans are thought to have arrived in Greenland around 2500 BC, Europeans didn’t know about the island until around the 10th century, when it was “discovered” by the Viking explorer Erik the Red. The Vikings established a few successful settlements that counted, at their peak, over 2,000 people. Archaeologists have uncovered the ruins of hundreds of farms and by what we can piece together, Norse life in Greenland was rough but manageable.

For a few centuries, the Vikings thrived. Then, around the 14th century, their population started to dwindle. They abandoned one of the biggest settlements and were decimated by attacks from the Inuit population (which also inhabited parts of Greenland). By the 15h century, the Viking settlements in Greenland had apparently been destroyed. Which begs an interesting question: why?

Not the cold

Of course, the first suspicion goes to low temperatures. Living in Greenland was rough anyway, but some experts suspected that the usual cold was compounded by the so-called Little Ice Age: a period of regional cooling, particularly pronounced in the North Atlantic region, that started hitting some areas in AD 1,300.

It seems to be a reasonable theory, but a new study finds no evidence to support it. Researchers from the University of Massachusetts Amherst and the University at Buffalo traveled to Greenland and extracted ice cores from a site adjacent to a former Norse farm and close to one of the largest groups of farms in the Eastern Norse Settlement. The team spent three years gathering ice cores and sediment samples from a lake which represent a continuous record of the past 2,000 years.

Previous studies that suggested a drop in temperature was to blame for the fall of the Viking settlements relied on samples gathered over 1,000 kilometers to the north and over 2,000 meters higher in elevation.

“Before this study, there was no data from the actual site of the Viking settlements. And that’s a problem,” says study coauthor Raymond Bradley, a UMass Amherst geosciences professor, in the statement. “We wanted to study how climate had varied close to the Norse farms themselves.”

“Nobody has actually studied this location before,” says Boyang Zhao, the study’s lead author who conducted this research for his Ph.D. in geosciences at UMass Amherst and is currently a postdoctoral research associate at Brown University.

The researchers measured something called BrGDGT — membrane lipids produced by bacteria in the soil that can serve as proxies for temperature and precipitation. They also measured a second marker from decaying plants and grasses which offers more indication of how dry it was at the time the plants were growing.

The data showed that while temperatures didn’t decrease substantially, one thing that changed was precipitation. Steadily, the Norse settlements suffered more and more droughts.

“What we discovered is that, while the temperature barely changed over the course of the Norse settlement of southern Greenland, it became steadily drier over time,” Zhao explains.

The straw that broke the Vikings’ back

Harsh winters in Greenland were no joke, and the Vikings wouldn’t have been able to support themselves from the farms alone. They likely supplemented their diets with seafood and trade. Even on a good year, the Norse farmers would have required supplies of dried grouse to feed livestock during the winter, and on bad years, they were likely never too far from food collapse.

In fact, previous studies already showed that while seafood initially made up no more than 30% of the Greenland Vikings’ food, by the 14th century, it comprised up to 80% of their diet. Trade also shriveled up, as the market for walrus tusks and seal skins (goods that Greenland colonists offered for trade) dwindled. Ships passing through Greenland became fewer and fewer, until they almost stopped coming altogether.

The Black Plague that ravaged Iceland and Scandinavia also left plenty of openings, possibly prompting many Greenlanders to head for greener pastures. Add droughts on top of all of this and it’s no surprise that the Vikings just couldn’t take it anymore. It’s unclear why, but the Inuits also attacked them, which spelled the end of the Norse settlements in Greenland.

In 1721, the Denmark-Norway kingdom sent a missionary expedition to Greenland to reinstate Christianity among descendants of the Norse Greenlanders who may have reverted to paganism. They were expecting descendants of the Norse to still be in Greenland, but none were to be found. Instead, they found Inuits living there instead — so they baptized them and established trade with Greenland, bringing the island back under Scandinavian control.

The study has been published in Science Advances.