The timberline varies from 700 m above sea level in the southern portion of the chain to 400 m in its northerly portion. The country's forest soils chiefly consist of moraines which were deposited when the inland ice cap melted 10,000 years ago. Most Swedish forests are part of the Boreal coniferous belt. Leaching of mineral nutrients has thus reduced their level by half in recent decades. Critical loads are being exceeded, both in terms of sulfur dioxide and nitrogen dioxide deposits.
Air pollution poses a serious threat to the forest eco system and to the growth of forests.
Only in the northern interior are the forests less affected by humans. Today these virgin-like forests are largely protected, either as nature reserves or by other means. In southern Sweden and other regions of the country with a long agricultural tradition, forests served as a source of wood for construction, fuel and the production of numerous useful objects and tools in an overwhelmingly agrarian society. For a long time, especially in southern and southwestern Sweden, farmers cut and burned forests to create fields for short-term cultivation, thereby depleting nutrients from the soil. As early as the Middle Ages, the forests supplied raw materials used in important Swedish export products.