ABSTRACT
Ecosystem types similar to those in the Arctic reach south of the southern limits in the mountains that extend into the Arctic from the boreal region in both Eurasia and North America. Many species in the Low Arctic have their main distribution south of the Arctic, e.g., in the boreal forest but extend into the tundra, although they mix with an increasing number of arctic species in the northern part of the zone. The arctic ecosystems are strongly detritus-based with an input of dead organic matter to the soil of appreciably above 95% of the annual net primary production in most arctic ecosystems. The terrestrial ecosystems of the Arctic which are mostly young and still developing are already facing many threats, and all of them from human activities. Local and transboundary pollution affects plants, soils and animals in some areas of the Arctic.
