Structure: Undrained habitats
Undrained habitats retain water. Draining of mires, forest land and agricultural land cause deficiency in water retention.
Pristine mires have a high capacity to store water and to slow down the water currents in the soil. The discharge of water is significantly larger in drained mires. Mires have been drained for silvicultural and agricultural purposes. In southern Finland about 80% of the total mire area has been drained and in northern Finland the same share is 40%. Mires cover about one third of the total land area of Finland.
In agricultural lands drainage is a very common procedure. In 2013 about 70% of the utilised agricultural area was subsurface-drained, 20% had open ditches and 10% was undrained. During a period from 1940s to 1970s the area under agriculture was somewhat higher than today, approximately 2.5 million hectares. In recent decades the area has remained quite stable at about 2.2 million hectares.
Draining of forest land reduces the water retention capacity. Since the 1960s first-time draining has affected nearly 5 million hectares of land under forestry. In the 2000s the first-time draining has ceased but ditch cleaning continues. In 2012 ca. 52 000 hectares of land was affected by ditch cleaning. The annual area has been decreasing in recent years. More than half of the drainage network has been re-drained.
National Forest Inventory (NFI). Finnish Forest Research Institute.
Utilised agricultural area. Agricultural Statistics.
Farmland management and irrigation. Agricultural Statistics.
Finnish Statistical Yearbooks of Forestry. Finnish Forest Research Institute.
- Updated (20.01.2015)