Collapse: How Societies Choose to Fail or Succeed (41 page)

bogs by palynologists, the scientists who study pollen and whose insights
into the vegetational history of Easter Island and the Maya area we already
encountered (Chapters 2 and 5). Drilling down into the mud at the bottom
of a lake or bog may not strike the rest of us as exciting, but it's nirvana for a
palynologist, because the deeper mud layers were deposited longer ago in the past. Radiocarbon dating of organic materials in a mud sample estab
lishes when that particular layer of mud settled out. Pollen grains from dif
ferent plant species look different under the microscope, so that the pollen
grains in your (you the palynologist's) mud sample tell you what plants
were growing near your lake or bog and were releasing pollen that fell into it
in that year. As past climates became colder in Greenland, palynologists find pollen shifting from that of warmth-demanding trees to that of cold-
tolerant grasses and sedges. But that same shift in pollen may also mean that the Norse were cutting down trees, and palynologists have found other ways
to distinguish those two interpretations of declining tree pollen.

Finally, by far our most detailed information about Greenland climates
in the past comes from ice cores. In Greenland's cold and intermittently wet
climate, trees are small, grow only locally, and their timber deteriorates
quickly, so we don't have for Greenland the logs with beautifully preserved
tree rings that have enabled archaeologists to reconstruct year-to-year cli
mate changes in the dry U.S. southwestern deserts inhabited by the Anasazi. Instead of tree rings, Greenland archaeologists have the good fortune of be
ing able to study ice rings
—or, actually, ice layers. Snow that falls each year
on Greenland's ice cap becomes compressed by the weight of later years of snow into ice. The oxygen in the water that constitutes snow or ice consists
of three different isotopes, i.e., three different types of oxygen atoms differ
ing just in atomic weight because of different numbers of uncharged neutrons in the oxygen nucleus. The overwhelmingly prevalent form of natural
oxygen (99.8% of the total) is the isotope oxygen-16 (meaning oxygen of atomic weight 16), but there is also a small proportion (0.2%) of oxygen-18,
and an even smaller amount of oxygen-17. All three of those isotopes are
stable, not radioactive, but they can still be distinguished by an instrument called a mass spectrometer. The warmer the temperature at which snow
forms, the higher is the proportion of oxygen-18 in the snow's oxygen.
Hence each year's summer snow is higher in its proportion of oxygen-18
than the same year's winter snow. For the same reason, snow oxygen-18 in a
given month of a warm year is higher than in the same month of a cold year.

Thus, as you drill down through the Greenland ice cap (something that

Greenland-ice-cap-drilling scientists have now done down to a depth of al
most two miles) and measure the oxygen-18 proportion as a function of
depth, you see the oxygen-18 proportion wiggling up and down as you bore
through one year's summer ice into the preceding winter's ice and then into the preceding summer's ice, because of the predictable seasonal changes in
temperature. You also find oxygen-18 values to differ among different sum
mers or different winters, because of unpredictable year-to-year fluctua
tions in temperature. Hence the Greenland ice core yields information
similar to what archaeologists studying the Anasazi deduce from tree rings:
it tells us each year's summer temperature and each year's winter tempera
ture, and as a bonus the thickness of the ice layer between consecutive sum
mers (or between consecutive winters) tells us the amount of precipitation
that fell during that year.

There is one other feature of weather about which we can learn from ice
cores, but not from tree rings, and that is storminess. Storm winds pick up
salt spray from the ocean around Greenland, may blow it far inland over the
ice cap, and drop there some of the spray frozen as snow, including the sodium ions in seawater. Onto the ice cap, storm winds also blow atmo
spheric dust, which originates far away in dry dusty areas of the continents,
and that dust is high in calcium ions. Snow formed from pure water lacks
those two ions. When one finds high concentrations of sodium and calcium
in an ice layer of the ice cap, it may mean that that was a stormy year.

In short, we can reconstruct past Greenland climates from Icelandic records, pollen, and ice cores, and the latter let us reconstruct climate on a
year-to-year basis. What have we thereby learned?

As expected, we've learned that the climate warmed up after the end of
the last Ice Age around 14,000 years ago; the fjords of Greenland became
merely "cool," not "bitterly cold," and they developed low forests. But
Greenland's climate hasn't remained boringly steady for the last 14,000
years: it has gotten colder for some periods, then reverted to being milder
again. Those climate fluctuations were important to the settling of Green
land by Native American peoples before the Norse. While the Arctic has few
prey species
—notably reindeer, seals, whales, and fish—those few species
are often abundant. But if the usual prey species die out or move away, there
may be no alternative prey for hunters to fall back on, as they can at lower latitudes where species are so diverse. Hence the history of the Arctic, in
cluding that of Greenland, is a history of people arriving, occupying large
areas for many centuries, and then declining or disappearing or having to

change their lifestyle over large areas when climate changes bring changes in
prey abundance.

Such consequences of climate changes for native hunters have been ob
served firsthand in Greenland during the 20th century. A warming of sea temperatures early in that century caused seals almost to disappear from
southern Greenland. Good seal hunting returned when the weather got
cooler again. Then, when the weather got very cold between 1959 and 1974,
populations of migratory seal species plummeted because of all the sea ice,
and total sea catches by native Greenland seal hunters declined, but the
Greenlanders avoided starvation by concentrating on ringed seals, a species
that remained common because it makes holes in the ice through which
to breathe. Similar climate fluctuations with consequent changes in prey
abundance may have contributed to the first settlement by Native Ameri
cans around 2500
b.c.,
their decline or disappearance around 1500
b.c.,
their subsequent return, their decline again, and then their complete aban
donment of southern Greenland some time before the Norse arrived around
a.d.
980. Hence the Norse settlers initially encountered no Native Ameri
cans, though they did find ruins left by former populations. Unfortunately
for the Norse, the warm climate at the time of their arrival was simultane
ously allowing the Inuit people (alias Eskimos) to expand quickly eastwards
from Bering Strait across the Canadian Arctic, because the ice that had per
manently closed the channels between northern Canadian islands during
cold centuries began to melt in the summer, permitting bowhead whales,
the mainstay of Inuit subsistence, to penetrate those Canadian Arctic water
ways. That climate change allowed the Inuit to enter northwestern Green
land from Canada around
a.d.
1200
—with big consequences for the Norse.

Between
a.d.
800 and 1300, ice cores tell us that the climate in Green
land was relatively mild, similar to Greenland's weather today or even slightly warmer. Those mild centuries are termed the Medieval Warm
Period. Thus, the Norse reached Greenland during a period good for growing hay and pasturing animals
—good by the standards of Greenland's average climate over the last 14,000 years. Around 1300, though, the climate in
the North Atlantic began to get cooler and more variable from year to year,
ushering in a cold period termed the Little Ice Age that lasted into the
1800s. By around 1420, the Little Ice Age was in full swing, and the in
creased summer drift ice between Greenland, Iceland, and Norway ended ship communication between the Greenland Norse and the outside world.
Those cold conditions were tolerable or even beneficial for the Inuit, who

could hunt ringed seals, but were bad news for the Norse, who depended on
growing hay. As we shall see, the onset of the Little Ice Age was a factor be
hind the demise of the Greenland Norse. But the climate shift from the Me
dieval Warm Period to the Little Ice Age was complex, and not a simple
matter that "it got steadily colder and killed off the Norse." There had been
sprinklings of cold periods before 1300 that the Norse survived, and sprin
klings of warm periods after
a.d.
1400 that failed to save them. Above all,
there remains the nagging question: why didn't the Norse learn to cope with
the Little Ice Age's cold weather by watching how the Inuit were meeting the
same challenges?

To complete our consideration of Greenland's environment, let's mention
its native plants and animals. The best-developed vegetation is confined to
areas of mild climate sheltered from salt spray in the long inner fjords of the
Western and Eastern Settlements on Greenland's southwest coast. There,
vegetation in areas not grazed by livestock varies by location. At higher ele
vations where it is cold, and in the outer fjords near the sea where plant
growth is inhibited by cold, fog, and salt spray, the vegetation is dominated
by sedges, which are shorter than grasses and have lower nutritional value
to grazing animals. Sedges can grow in these poor locations because they
are more resistant to drying out than are grasses, and they can thus establish
themselves in gravel containing little water-retaining soil. Inland in areas
protected from salt spray, the steep slopes and cold windy sites near glaciers
are virtually bare rock without vegetation. Less hostile inland sites mostly
support a heath vegetation of dwarf shrubs. The best inland sites
—i.e., ones at low elevation, with good soil, protected from the wind, well watered, and
with a south-facing exposure that lets them receive much sunlight—carry
an open woodland of dwarf birch and willows with some junipers and
alders, mostly less than 16 feet tall, in the very best sites with birches up to
30 feet tall.

In areas grazed today by sheep and horses, the vegetation presents a dif
ferent picture, and would have in Norse times as well (Plate 17). Moist
meadows on gentle slopes, such as those around Gardar and Brattahlid, have
lush grass up to one foot high, with many flowers. Patches of dwarf willow
and birch grazed down by sheep reach only a foot-and-a-half in height.
Drier, more sloping and exposed fields carry grasses or dwarf willow up to
only a few inches high. Only where grazing sheep and horses have been ex
cluded, such as within the perimeter fence around Narsarsuaq Airport, did I

see dwarf willows and birches up to seven feet tall, stunted by cold wind
coming off a nearby glacier.

As for Greenland's wild animals, the ones potentially most important to the Norse and Inuit were land and sea mammals and birds, fish, and marine
invertebrates. Greenland's sole native large terrestrial herbivore in the former Norse areas (i.e., not considering the musk ox in the far north) is the
caribou, which Lapps and other native peoples of the Eurasian continent domesticated as reindeer but which the Norse and Inuit never did. Polar
bears and wolves were virtually confined in Greenland to areas north of the Norse settlements. Smaller game animals included hares, foxes, land birds (of which the largest were grouse relatives called ptarmigans), freshwater
birds (the largest being swans and geese), and seabirds (especially eider
ducks and auks, a.k.a. alcids). The most important marine mammals were
seals of six different species, differing in significance to the Norse and Inuit,
related to differences in their distribution and behavior that I shall explain
below. The largest of these six species is the walrus. Various species of
whales occur along the coast, and were successfully hunted by the Inuit but not by the Norse. Fish abounded in rivers, lakes, and oceans, while shrimp and mussels were the most valuable edible marine invertebrates.

According to sagas and medieval histories, around the year 980 a hot-
blooded Norwegian known as Erik the Red was charged with murder and
forced to leave for Iceland, where he soon killed a few more people and was
chased out to another part of Iceland. Having ended up, there too, in a
quarrel and killed still more people, he was this time exiled entirely from
Iceland for three years beginning around 982.

Erik remembered that, many decades earlier, one Gunnbjorn Ulfsson
had been blown westwards far off course while sailing for Iceland and had spotted some barren small islands, which we now know lay just off Green
land's southeast coast. Those islands had been revisited around 978 by
Erik's distant relative Snaebjorn Galti, who of course got into a quarrel of
his own there with his shipmates and was duly murdered. Erik sailed for
those islands to try his luck, spent the next three years exploring much of
the Greenland coast, and discovered good pastureland inside the deep
fiords. On his return to Iceland he lost yet another fight, impelling him to
lead a fleet of 25 ships to settle the newly explored land that he shrewdly named Greenland. News brought back to Iceland of the fine homesteads
available for the asking in Greenland motivated three more fleets of settlers