Collapse_ How Societies Choose to Fail or Succeed - Jared Diamond [134]
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 Greenland 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 dies out or moves 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, including 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 observed 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 Americans around 2500 B.C., their decline or disappearance around 1500 B.C., their subsequent return, their decline again, and then their complete abandonment of southern Greenland some time before the Norse arrived around A.D. 980. Hence the Norse settlers initially encountered no Native Americans, though they did find ruins left by former populations. Unfortunately for the Norse, the warm climate at the time of their arrival was simultaneously allowing the Inuit people (alias Eskimos) to expand quickly eastwards from Bering Strait across the Canadian Arctic, because the ice that had permanently 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 waterways. That climate change allowed the Inuit to enter northwestern Greenland 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 Greenland 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 increased 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