In Norway, land use changes have led to increased erosion and decreased biodiversity. Norwegian agriculture was significantly restructured in the 1950s. Dairy farming was concentrated in the western and northwestern parts of the country. Arable farming was directed to the southeast. The consequences were that mixed farms in the southeast had to shift to pure crop farming and that many old pastures had to be transformed into arable farming land. After 1950, agriculture became more intensive with the introduction of more efficient and heavy machinery, increased fertilisation and new cropping systems. Agricultural fields were consolidated, small areas of semi-natural vegetation and field margins disappeared. The consequence of the restructuring and intensification was that land with a more limited crop production potential changed into arable farming land. During the 1980s the negative consequences of these changes became evident: increased erosion, pollution of rivers and lakes by nitrogen and phosphorus, disappearance of the cultural landscape heritage and loss of biodiversity. In 1988/89 an algal bloom caused the death of many marine organisms in both North Sea and Skagerrak. Eutrification by nitrogen and phosphorus was identified as the cause for the enormous increase in poisonous algae. European countries bordering the North Sea agreed on a plan to reduce nutrient run-off (North Sea Declaration). The Norwegian government decided to prioritise the reduction of erosion and a soil mapping programme was established for the watersheds feeding into the North Sea and Skagerrak. Soil erosion in Norway mainly occurs in autumn and spring. In autumn, heavy rainfall on already saturated soils can cause soil loss through (increased) surface run-off. In spring, erosion is caused by heavy snowmelt, sometimes in combination with frozen (sub)soil. In order to reduce erosion, it was decided to use the Norwegian Soil Information System as a basic instrument.