By Sergei ZIMOV, Chief of the Northeastern Research Station of the Pacific Institute of Geography of the RAS Far Eastern Branch Man's appearance and his settlement across the world are closely bound up with the development of pasture ecosystems. Having ousted forests in the latest ice age, pastures occupied them most of the earth's land surface. Their soils in the form of a thick permafrost sheet even now cover North Siberian plains. It serves as the world's largest stock of organic carbon. What is to become with the world climate if permafrost starts thawing? Can pasture ecosystems stem the process? стр. 105 FROM PLEISTOCENE TO HOLOCENE By advancing and retreating, the giant ice sheets have been plowing the north of Europe and America* in the past million years. However, the situation in North Siberia was relatively calm in geological terms in the Pleistocene** epoch: erosion prevailed in the mountains and silt and dust were accumulated in the vast plains and valleys. Life did not come to a standstill even in the highest latitudes. Mammoths, woolly rhinoceroses, bisons, horses, reindeer***, musk oxen, ancestors of red deer, elks, saigas and yaks then grazed on grassy pastures. Beasts of prey - tiger-lions and wolves - never went hungry. In winter ground cracked at low freezing temperatures, with water collected in deep cracks. As it froze, thin ice veins were formed. The process went on for thousands of years and, as a result, a many-meter-thick sheet of silty loam pierced by crisscrossed ice veins covered northern plains. In fact, it is nothing but permafrost soils of the prehistoric period's largest ecosystem of mammoth tundra steppes. And the thick layer filled with grass roots, live microorganisms and animal bones is a detailed record of the ecosystem's development. At the peak of the ice age it encompassed the territory from what is now France to Canada, from the Arctic Islands to Northern China. But at the start of the ... Read more