It was probably drought rather than the Little Ice Age
From: The University of Massachusetts Amherst
March 23, 2022 -- One
of the great mysteries of late medieval history is why did the Norse, who had
established successful settlements in southern Greenland in 985, abandon them
in the early 15th century?
The consensus view has
long been that colder temperatures, associated with the Little Ice Age, helped
make the colonies unsustainable. However, new research, led by the University
of Massachusetts Amherst and published recently in Science Advances, upends
that old theory. It wasn’t dropping temperatures that helped drive the Norse
from Greenland, but drought.
When the Norse settled
in Greenland on what they called the Eastern Settlement in 985, they thrived by
clearing the land of shrubs and planting grass as pasture for their livestock.
The population of the Eastern Settlement peaked at around 2,000 inhabitants,
but collapsed fairly quickly about 400 years later.
For decades,
anthropologists, historians and scientists have thought the Eastern
Settlement’s demise was due to the onset of the Little Ice Age, a period of exceptionally
cold weather, particularly in the North Atlantic, that made agricultural life
in Greenland untenable.
However, as Raymond
Bradley, University Distinguished Professor of geosciences at UMass Amherst and
one of the paper’s co- author, points out,
“Before this study,
there was no data from the actual site of the Viking settlements. And that’s a
problem.”
Instead, the ice core
data that previous studies had used to reconstruct historical temperatures in
Greenland was taken from a location that was over 1,000 kilometers to the north
and over 2,000 meters higher in elevation. “We wanted to study how climate had
varied close to the Norse farms themselves,” says Bradley. And when they did,
the results were surprising.
Bradley and his
colleagues traveled to a lake called Lake 578, which is adjacent to a former
Norse farm and close to one of the largest groups of farms in the Eastern
Settlement. There, they spent three years gathering sediment samples from the
lake, which represented a continuous record for the past 2,000 years.
“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.” -- says Zhao
They then analyzed that
2,000 year sample for two different markers: the first, a lipid, known as
BrGDGT, can be used to reconstruct temperature. “If you have a complete enough
record, you can directly link the changing structures of the lipids to changing
temperature,” says Isla Castañeda, professor of geosciences 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 the grasses and other livestock-sustaining plants lost water due
to evaporation. It is therefore an indicator of how dry conditions were.
“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.” says Zhao
Norse farmers had to
overwinter their livestock on stored fodder, and even in a good year the
animals were often so weak that they had to be carried to the fields once the
snow finally melted in the spring. Under conditions like that, the consequences
of drought would have been severe. An extended drought, on top of other
economic and social pressures, may have tipped the balance just enough to make
the Eastern Settlement unsustainable.
Scientists at Smith
College and the University at Buffalo also contributed to the research, which
was supported by the National Science Foundation, UMass Amherst, the Geological
Society of America, and the Swiss National Science Foundation, changes our
understanding of early European history, and highlights the importance of continuing
to explore how environmental factors influence human society. The new
findings change our understanding of early European history and highlight the
importance of continuing to explore how environmental factors influence human
society.
https://www.umass.edu/news/article/rewriting-history-books-why-vikings-left-greenland
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