Cost-Benefit Analysis of continuous cover forestry and buffer zones as Nature Based Solutions to preserve water quality level in Lake Puruvesi and in its sub-catchment area.

Mitigation of the perceived risks of climate change is urgent issue in many fields. This research focuses on providing information to support decision making in mitigation of hydro-meteorological risks that climate change causes to the water quality in Lake Puruvesi and in its sub-catchment area. This study reviews continuous cover forestry (CCF) and buffer zones as possible nature-based solutions (NBS) that could achieve the goal of keeping the water quality level in study site on current level or improve it. The main research question of this research is: Is it economically cost-efficient to implement continuous cover forestry and buffer zones as nature-based solutions to mitigate nutrient loading in research area so that the water quality will stay at least at the current level in the future?

Previous research has shown that CCF can be economically feasible way to manage forests. In addition to this, continuous cover forestry and buffer zones can reduce nutrient loading from forests to nearby waters. These solutions are evaluated in the framework of cost-benefit analysis which is the main method in this study. The aim is to monetize costs and benefits that NBS implementation will cause. If the net social benefits after analysis are positive, the project should be recommended. In this study recreation values from the study site were obtained by utilizing pre-existing valuation studies made by Finnish Natural Resource Center. Costs on the other hand were derived by using size-structured forest optimization model. The economic loss for forest owners is the difference between their optimal forest management choice, and the optimized solution, where clearcutting is restricted. In the buffer zone case optimization was similar but the costs from buffer zones are directly the maximized profits from forest as the buffer zone is completely left out from any forestry.

In both cases CCF was the optimal forest management regime for the sample forests. When these costs were compared to the benefits this study produced positive net social benefits and hence CCF and buffer zones should be recommended as NBS in the study site. However, there are quite large assumptions made in this study, and further modeling of nutrient flow in study site is required as the quantified impacts of nutrient run-off are still unclear. For this reason, further research is required for more precise analysis regarding quantified impacts.