The emergence of the Aletsch forest is documented in a special archive, namely in bogs, which have been formed in rock hollows within the forest. Taking out a drilling core sample from a deep bog, the development of the vegetation can be reconstructed with the pollen analysis on the basis of pollen contained in the peat. The development of the Aletsch forest began after the retreat of the Great Aletsch glacier at the end of the Ice Age 11.700 years ago. The immigration of the plants was similar to today’s glacier forefield: first grew grasses and herbs, followed shortly thereafter by birch and willow. The larch immigrated around 8500 years ago and the Swiss stone pine 8000 years ago. Today the Swiss stone pine is the dominant tree species with 63 % of the trees in the Aletsch forest, followed by the larch with 27 %. Investigations have shown that the oldest stone pine and larch trees are between 500 and 600 years old. Thousand years old trees have not been found so far.