Sensitive mountain lakes. Photo: Naturcentrum AB.Sensitive mountain lakes. Photo: Naturcentrum AB.

Acid soil cannot tolerate


The bouldery, nutrient-poor soil, especially around the lakes Rogen, Femunden and Feragen, contains almost no lime or other minerals that neutralise or increase the pH level. This is why lakes in the area are very sensitive to acidification. When polluted acid rain fell over the area from the 1960s to the 1980s, the pH values decreased drastically. The lakes became so acidic that fish roe and fry found it hard to survive. To counteract the acidification, the Norwegian authorities started liming in the Femunden area in 1984. Liming of the catchment area of the river Storån in Sweden started in 1987, and a year later liming in the Rogen area was carried out from the air. The lime has given new life to the water, and both insects and brown trout have increased significantly. Fishermen can attest that the fish are biting again.

Soil acidification means that more acidic substances are deposited on the soil and in watercourses than what is carried away.