The data were mainly collected from the National Forest Inventory database (NAFI) but also several other sources were used. However, when Finland started the 15% restoration prioritization project in the beginning of the year 2014, the four degradation levels were abandoned. This model is briefly described in chapter 6. An erosion classification system, the AUI Farmland Database (Nytjaland),8 the Iceland Forestry Service database and expert knowledge were used for a first attempt to propose a degradation classification for habitats to this project. An erosion classification system was developed in the 1990s and all land assigned to six classes (Arnalds et al. These were no erosion (0), little erosion (1), slight erosion (2), considerable erosion (3), severe erosion (4) and extremely severe erosion (5).