Fine-scale conservation planning outside of reserves: Cost-effective selection of retention patches at final harvest

Retaining forest patches at final harvest is a key conservation measure in boreal forests, but guidelines for how to increase its cost-effectiveness are lacking. In a study in boreal Sweden, we compared the cost-effectiveness of three different approaches a forest owner may use to select patches: selection based on the conservation value of patches alone, economic cost alone or both of them combined. We also compared the cost-effectiveness of six different common types of patches. Conservation value was measured as species richness of bryophytes and lichens and as structural characteristics of patches. Compared to the selection approach in which both conservation value and cost were used, cost-effectiveness was 5-14% lower when only conservation value was used, depending on how conservation value was measured. On the contrary, using only the economic cost decreased the cost-effectiveness by only 1-2%. Among the patch types, swamp forest areas and deciduous tree groups were cost-effective types to retain. However, the patch types were complementary in their species composition and all hosted unique species. We argue that, ideally, assessments of both conservation values and economic costs of retaining patches should be made prior to harvest to enable planners to make well-informed and cost-effective decisions.