Impact of Sitka spruce on biodiversity in NW Europe with a special focus on Norway – evidence, perceptions and regulations

The impact of historical and present drivers on biodiversity, particularly species richness and abundance, in afforestation areas concerning non-native tree species is still poorly understood. A better understanding is important to ensure appropriate forest management in the face of climate change and increasing demand for wood products. Here, we have reviewed 75 biodiversity studies in Sitka spruce plantations in NW Europe, forest management recommendations for maintaining biodiversity, timber production and carbon sequestration in Sitka spruce forests in coastal Norway compared to NW Europe. Due to more focus on non-market landscape benefits and protection sites in coastal areas, transformation of spruce plantations is common. Premature cutting of stands and shelterbelts and clearing away saplings has become the dominant management practice in Norway. Based on the extent of use in Norway, and results from biodiversity studies in Sitka spruce plantations in NW Europe, the quality of evidence for the prevailing practice and recommendations in coastal Norway is highly questioned. To reduce conflicts, we propose a more knowledge-based management, a broader perspective underpinning the range of afforestation goals, also including the use of alternative silvicultural methods to increase structural variation in Sitka spruce stands.