Long-term impacts of increased timber harvests on ecosystem services and biodiversity: A scenario study based on national forest inventory data

The transition to a climate-neutral economy is expected to increase future timber demands and endanger the multifunctionality of forests. National scenario analyses are needed to determine long-term forest management impacts and support forest policy making in defining guidelines for the sustainable provision of forests’ ecosystem services and biodiversity (ESB). Using national forestry inventory data, the forest management model MASSIMO and a model to estimate harvesting costs, we simulated forest development in Switzerland under five politically relevant timber harvesting scenarios until 2106 (business as usual and four increased timber mobilisation scenarios). Model results were analysed using a utility-based multi-criteria approach regarding timber production, protection against gravitational hazards, carbon sequestration and biodiversity conservation for the whole of Switzerland and for five sub-regions. The development of ESB benefits over time and existing trade-offs were analysed. Apart from the Plateau region, the business-as-usual scenario resulted in the highest overall ESB benefits. However, this scenario did not mobilise possible timber potentials, which is not in line with current forest policies. In the Plateau region, ESB benefited most under a constant growing stock scenario that guaranteed long-term sustainable timber usage. Nevertheless, both scenarios showed strong trade-offs between biodiversity conservation and the service carbon sequestration. The latter was achieved best under a scenario with conifer promotion and increased harvested timber volumes that can be used for long-living timber products and substitution of energy intensive materials and fossil fuels. Even though weighting the ESB according to regional management priorities further increased the trade-off situation, it also increased the overall benefits of harvesting scenarios, except for in mountainous regions. We conclude that no single scenario can maximize all ESB benefits simultaneously. A combination of locally adapted scenarios with targeted priorities can guarantee a higher degree of multifunctionality and long-term timber supply, but at the cost of locally more accentuated trade-offs. Overall, our study provides new insights into ESB interactions, and the presented multi-criteria framework and results provide a valuable basis to support forest policy decision making in Switzerland and beyond.