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.In those sediments oc-cur at least five environmental indicators: whole plant parts such as leaves, and plant pollen, both of which serve to identify the plant species growing near the lake at that time; charcoal particles, proof of fires nearby; magnetic susceptibility measurements, which in Greenland reflect mainly the amounts of magnetic iron minerals in the sediment, arising from topsoil washed or blown into the lake's basin; and sand similarly washed or blown in.These studies of lake sediments yield the following picture of vegeta-tional history around the Norse farms.As temperatures warmed up at the end of the last Ice Age, pollen counts show that grasses and sedges became replaced by trees.For the next 8,000 years there were few further changes in the vegetation, and few or no signs of deforestation and erosion—until the Vikings arrived.That event was signaled by a layer of charcoal from Viking fires to clear pastures for their livestock.Pollen of willow and birch trees decreased, while pollen of grasses, sedges, weeds, and pasture plants introduced by the Norse for animal feed rose.Increased magnetic susceptibility values show that topsoil was carried into lakes, the topsoil having lost the plant cover that had previously protected it from erosion by wind and water.Finally, sand underlying the topsoil also was carried in when whole valleys had been denuded of their plant cover and soil.All of these changes became reversed, indicating recovery of the landscape, after the Viking settlements went extinct in the 1400s.Finally, the same set of changes that accompanied Norse arrival appeared all over again after 1924, when the Danish government of Greenland reintroduced sheep five centuries after their demise along with their Viking caretakers.So what?—an environmental skeptic might ask.That's sad for willow trees, but what about people? It turned out that deforestation, soil erosion, and turf cutting all had serious consequences for the Norse.The most obvious consequence of deforestation was that the Norse quickly became short of lumber, as did the Icelanders and Mangarevans.The low and thin trunks of the willow, birch, and juniper trees remaining were suitable for making only small household wooden objects.For large pieces of wood to fashion into beams of houses, boats, sledges, barrels, wall panels, and beds, the Norse came to depend on three sources of timber: Siberian driftwood washed up on the beaches, imported logs from Norway, and trees felled by the Green-landers themselves on voyages to the Labrador coast ("Markland") discovered in the course of the Vinland explorations.Lumber evidently remained so scarce that wooden objects were recycled rather than discarded.This can be deduced from the absence of large wooden panels and furniture at most Greenland Norse ruins except for the last houses in which the Norse ofWestern Settlement died.At a famous Western Settlement archaeological site called "Farm Beneath the Sands," which became almost perfectly preserved under frozen river sands, most timber found was in the upper layers rather than in the lower layers, again suggesting that timber of old rooms and buildings was too precious to discard and was scavenged as rooms were remodeled or added.The Norse also dealt with their poverty in timber by resorting to turf for walls of buildings, but we shall see that that solution posed its own set of problems.Another answer to the "so what?" response to deforestation is: poverty in firewood.Unlike the Inuit, who learned to use blubber for heating and lighting their dwellings, remains in Norse hearths show that the Norse continued to burn willow and alder wood in their houses.A major additional demand for firewood that most of us modern city-dwellers would never think of was in the dairy.Milk is an ephemeral, potentially dangerous food source: it is so nourishing, not only to us but also to bacteria, that it quickly spoils if left to stand without the pasteurization and refrigeration that we take for granted and that the Norse, like everyone else before modern times, didn't practice.Hence the vessels in which the Norse collected and stored milk and made cheese had to be washed frequently with boiled water, twice a day in the case of milk buckets.Milking animals at saeters (those summer farm buildings in the hills) was consequently confined to elevations below 1,300 feet, above which firewood was unavailable, even though pasture grasses good for feeding livestock grew up to much higher elevations of about 2,500 feet.In both Iceland and Norway we know that saeters had to be closed down when local firewood became exhausted, and the same presumably held for Greenland as well.Just as was true for scarce lumber, the Norse substituted other materials for scarce firewood, by burning animal bones, manure, and turf.But those solutions too had disadvantages: the bones and manure could otherwise have been used to fertilize fields for increased hay production, and burning turf was tantamount to destroying pasture.The remaining heavy consequences of deforestation, besides shortages of lumber and firewood, involved shortages of iron.Scandinavians obtained most of their iron as bog iron—i.e., by extracting the metal from bog sediments with low iron content.Bog iron itself is locally available in Greenland, as in Iceland and Scandinavia: Christian Keller and I saw an iron-colored bog at Gardar in the Eastern Settlement, and Thomas McGov-ern saw other such bogs in the Western Settlement [ Pobierz całość w formacie PDF ]