(CNN)Norse populations in Greenland vanished in the 15th century, and the reason has been a mystery for centuries. However, a recent study of medieval artifacts from across Europe suggests it may have been due to the over-hunting of walrus.
Vikings disappeared from Greenland due to over-hunting walrus, study suggests
The ivory from walrus tusks was a valuable commodity in medieval times, and Vikings often traded it with Europeans for iron and timber, according to James Barrett, the lead study author.
However, Barrett suspects that as the value of walrus ivory declined in Europe, it meant more tusks had to be collected in order to keep Norse colonies in Greenland economically viable.
It was previously theorized that as West African trade routes opened up, elephant ivory began to become more popular due to its homogenous finish, compared to the marbled look of walrus ivory, according to Barrett. But the researchers found evidence that the hunt for walrus ivory probably increased.
"Mass hunting can end the use of traditional haul-out sites by walruses," said Barrett in a statement. "Our findings suggest that Norse hunters were forced to venture deeper into the Arctic Circle for increasingly meager ivory harvests. This would have exacerbated the decline of walrus populations, and consequently those sustained by the walrus trade."
The study authors looked at 67 rostra -- the walrus skull and snout to which the tusks were attached -- from across Europe between the 11th and 15th centuries. What they found was that in the 13th century, there was a shift in walrus from an evolutionary branch farther north from where Greenland Norse typically hunted.
"As the unit value of walrus ivory declined, the Norse Greenlanders had to hunt more and more to maintain the same level of trade with Europe to make ends meet," Barrett tells CNN. "In the face of global economic changes their hunting may have become unsustainable. Combined with other challenges of the time (e.g. climate change), they were put in a very difficult situation.
"Norse Greenland is often discussed as a cautionary tale for modern times. It is always risky to draw parallels between the past and the present, but there are contemporary resonances here. While trying to make ends meet we can all lose sight of the big picture -- the long-term consequen