Structure: Undisturbed habitats

Nutrient retention is strongly related to the water retention capacity of the soil and vegetation. Flowing water catches along loose nutrients and carry them into the water system. There are more loose nutrients available if the soil surface has been tilled or otherwise managed for example in farming or forestry processes.


Drainage of mires accelerates both the surface run-off of water as well as the release of nutrients. Drainage has been a common procedure both in agriculture and forestry and mires have been drained in Finland for both purposes. In southern Finland nearly 80% and in northern Finland 40% of the mire area was drained by the 2000s. Mires cover about one third of the total land area of Finland.


Farmlands are generally drained and annually tilled which both cause nutrient loss. Also too large fertilizer quantities or incorrect practices may increase the nutrient flow into the water system. The land area under farming has remained quite stable during the past decades, around 2.2 million ha. The share of untilled fallow  has been  approximately 12% in the 2000s. In recent decades the agricultural practices have been under modification in order to decrease the nutrient loss for example by underground draining and broadening the border strips.


Undisturbed forest vegetation and soil retain nutrients effectively by absorbing and filtering water and taking in the excessive nutrients. Forestry processes, nevertheless, cause nutrient loss by draining, felling and soil preparation. Since the 1960s first-time draining has affected nearly 5 million hectares of land under forestry. There are ca. 1.5 million km ditches in Finnish forests. In the 1970s and 1980s the draining and fertilizing caused the largest nutrient run-offs. In recent decades the regeneration fellings, soil preparation and ditch cleaning have been the largest culprits.


National Forest Inventory (NFI). Finnish Forest Research Institute.

Finnish Statistical Yearbooks of Forestry. Finnish Forest Research Institute.

Kenttämies, K. & Mattsson, T. (eds.) 2006. Metsätalouden vesistökuormitus. Suomen ympäristö 816. Suomen ympäristökeskus. [In Finnish]    


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