What Killed the Greenland (Viking) Colony?

Anglo-Saxon reliquary cross with walrus
ivory figure.  10th c. CE.  Source:
 Wikipedia (Modifications made by Johnbod).

It's well known that at least two Viking settlements were established in southern Greenland, sometime around the end of the Viking period. By about 1500 CE, however, archaeological evidence shows that the colony had died and its last colonists had either left or perished.  Why?

That's the question that archaeologists keep asking themselves.  It's true that the death of the colony comes during the so-called Little Ice Age, a time when the climate of Northern Europe in general and Greenland in particular became significantly colder.   But the Inuit, with whom the Greenland colonists had dealings, easily survived colder weather further north.

I'm writing about this question because it appears to be based, critically, upon food and food sources, making it relevant to this blog.  My immediate inspiration is this article from Science Magazine, which cites research that contradicts the currently popular theory on this question.

The popular theory was that the Scandinavian colonists refused to learn from the Inuit practice of living on arctic and subarctic marine mammals and continued to try to feed themselves with cattle and other agricultural products even after the climate had become too cold for such food sources to provide enough food to sustain them.  However, newer archaeological analysis and evidence tends to show that the Greenland colonists did turn to the sea, like the Inuit, for sustenance and trade:

• Excavations of the colonists' trash heaps shows that 60%-80% of the bones found were, not cattle or domesticated farm animals, but from seals.  That indicates that seals formed a large portion of the colonists' diet;
• Finds of buttons made from walrus ivory;
• Analysis of the bones of settlers, showing that, over the four centuries of the colonies' existence, the settlers ate increasing amounts of marine protein.

The article also notes that walrus ivory was highly prized in Europe and that there was great motive to hunt walrus for that reason, and the presence of walrus bone in the settlement trash heaps indicates that the rest of the walrus was not wasted.  Daniel Serra's book An Early Meal theorizes that the Vikings who did not leave Scandinavia probably ate more protein from the sea than had previously been assumed by scholars, especially during the lean time of the year (summer; after winter supplies of other foods had been exhausted but before the next harvest).  His research further supports the idea that the Norse in Greenland were not fatally averse to eating sea animals.  

Even more interestingly, other new evidence confirms that the settlers in Greenland did not practice wasteful agricultural techniques, as had previously been thought.  Newly gathered pollen and soil data shows that attention was paid to allowing fields and forests to recover after tilling and turf cutting, and that pastures were maintained with manure fertilizer and irrigation ditches.  

So what ended the colony?  The end probably was due to insufficient food, but that does not seem to have resulted from the colonists' intransigence and negligence as previously thought. Climate change made the once marginally viable possibility of agriculture in southern Greenland non-viable. Fishing may not have been sufficient for all the colony's needs (note that the evidence shows a steady increase in marine protein over time).  Economic changes may also have hastened the colony's end. According to the Science magazine article, some scholars now think that walrus ivory fell out of favor later in Europe during the late Middle Ages, when European visits to Africa brought increasing amounts of elephant ivory into European markets.   That suggests that walrus ivory was no longer sufficiently prized to make it possible to supplement the colonists' marine diet by trading walrus ivory for foodstuffs with the rest of Europe.

There is a lesson here, I think.  A neat, plausible, one-cause answer to a historical question is usually wrong--even if it comes from the experts!  Especially when it assumes that people from earlier times were willfully stupid about a survival matter such as food.