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By Root 1997 0

by professional soil scientists, but also because one of those differences was invisible at first sight and would take years to appreciate: namely, that Iceland’s soils form more slowly and erode much more quickly than those of Norway and Britain. In effect, when the settlers saw Iceland’s fertile and locally thick soils, they reacted with delight, as any of us would react to inheriting a bank account with a large positive balance, for which we would assume familiar interest rates and would expect the account to throw off large interest payments each year. Unfortunately, while Iceland’s soils and dense woodlands were impressive to the eye—corresponding to the large balance of the bank account—that balance had accumulated very slowly (as if with low interest rates) since the end of the last Ice Age. The settlers eventually discovered that they were not living off of Iceland’s ecological annual interest, but that they were drawing down its accumulated capital of soil and vegetation that had taken ten thousand years to build up, and much of which the settlers exhausted in a few decades or even within a year. Inadvertently, the settlers were not using the soil and vegetation sustainably, as resources that can persist indefinitely (like a well-managed fishery or forest) if harvested no faster than the resources can renew themselves. They were instead exploiting the soil and vegetation in the way that miners exploit oil and mineral deposits, which renew themselves only infinitely slowly and are mined until they are all gone.

What is it that makes Iceland’s soils so fragile and slow to form? A major reason has to do with their origin. In Norway, northern Britain, and Greenland, which lack recently active volcanoes and were completely glaciated during the Ice Ages, heavy soils were generated either as uplifted marine clays or else by glaciers grinding the underlying rock and carrying the particles, which were later deposited as sediment when the glaciers melted. In Iceland, though, frequent eruptions of volcanoes throw clouds of fine ash into the air. That ash includes light particles that strong winds proceed to carry over much of the country, resulting in the formation of an ash layer (tephra) that can be as light as talcum powder. On that rich fertile ash, vegetation eventually grows up, covering the ash and protecting it from erosion. But when that vegetation is removed (by sheep grazing it or farmers burning it), the ash becomes exposed again, making it susceptible to erosion. Because the ash was light enough to be carried in by the wind in the first place, it is also light enough to be carried out by the wind again. In addition to that wind erosion, Iceland’s locally heavy rains and frequent floods also remove the exposed ash by water erosion, especially on steep slopes.

The other reasons for the fragility of Iceland’s soils have to do with the fragility of its vegetation. Growth of vegetation tends to protect soil against erosion by covering it, and by adding organic matter that cements it and increases its bulk. But vegetaion grows slowly in Iceland because of its northerly location, cool climate, and short growing season. Iceland’s combination of fragile soils and slow plant growth creates a positive feedback cycle to erosion: after the protective cover of vegetation is stripped off by sheep or farmers, and soil erosion has then begun, it is difficult for plants to reestablish themselves and to protect the soil again, so the erosion tends to spread.

Iceland’s colonization began in earnest around the year 870 and virtually ended by the year 930, when almost all land suitable for farming had been settled or claimed. Most settlers came directly from western Norway, the remainder being Vikings who had already emigrated to the British Isles and married Celtic wives. Those settlers tired to re-create a herding economy similar to the lifestyle that they had known in Norway and the British Isles, and based on the same five barnyard animals, among which sheep eventually became by far the most numerous. Sheep milk was made