Investigating the prerequisites of a service guarantee for soil damages

Sammanfattning: Timber harvesting is a disturbance which can alter the natural order of the ecosystem, causing potentially harmful consequences, especially on water quality. These damages are commonly present where forestry machines have ruptured or compacted the organic layer of the forest floor. Therefore, protection of forest soil during forestry operations has become an increasing concern, and many forestry companies are actively working towards implementing soil protection strategies. SCA Skog AB proposed the possibility of implementing a service guarantee as a strategy to meet this goal. Therefore, this project was undertaken to investigate the prerequisites of creating a service guarantee for soil damages. In this study, the aim was to assess the possibilities to create a predictive model and to use the model result as an input to calculate the cost of implementing the service guarantee. A binomial logistic regression analysis method was used, and purposeful selection was chosen as the method of selecting variables for the predictive model. Data were provided by SCA Skog AB. The result of this investigation shows that the current dataset is not suitable for creating predictive models. Although it was possible to detect correlation between the independent variables, and rutting and severe rutting, it was not strong enough to be used in a prediction model. As it was not possible to predict the risk of rutting and revere Rutting, an average was calculated to provide the expected number of soil damages detected each year. Thus, the second aim, to calculate cost estimate intervals for a guarantee was possible to fulfill. Depending on the chosen Soil Damage Recovery Scenario, Assessment Sample Size, Employee option and Forest Owner Compensation, it was concluded that the implementation cost of the service guarantee should range between 347 028 and 2 012 254 SEK/year in total costs for the studied area, which would be equivalent to 0.41 - 2.25 SEK/m3sub (cubic meters, solid volume under bark).