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Forests in mountain regions provide an indispensable ecosystem service by protecting people and infrastructure against natural hazards. Thanks to this Nature-based Solution (NbS), costs of engineered technical protection measures can be reduced or even avoided. However, open questions remain about the long-term and sustainable provision of protective service by mountain forests, which are expected to be increasingly affected by climate change. More frequent and severe droughts as well as extreme events, such as forest fires or wind storms, can result in temporary or irreversible loss of the protective effect of forests. The uncertainties related to these changes pose great challenges for the sustainable management of these forests as well as settlements and infrastructure exposed to the natural hazard events. Thus, robust scenarios of the future development of the protective effect of forests are required to anticipate potential changes in natural hazard risks and adapt their management appropriately. In this study, we derived future scenarios of a rockfall protective forest in Switzerland by combining modeling with an expert-based evaluation. We therefore simulated the protective forest under future climate conditions with the dynamic forest landscape model TreeMig and evaluated the plausibility of the derived scenarios in a survey of 45 experts mainly from public forest management. First results show that they generally expect a significant decline of the current tree species in the next 50 to 100 yrs for the climate scenario RCP8.5. In contrast to the forest simulations, the experts forecast a clear dominance of oak species instead of Scots pine due to a higher drought tolerance. Furthermore, they emphasized the importance of other influencing factors, such as natural disturbances, browsing or forest diebacks due to diseases as well as compound events. Based on the plausibility assessment of the simulation results by the experts, the species parameters used in the simulation were adapted. In a next step, the influence of the different future forest scenarios on the protective effect against rockfall will be analyzed in more detail. Overall, the applied approach combining modeling with expert opinion allows for a more comprehensive analysis of the uncertainties related to climate change and extreme events, especially if quantitative data is scarce.
Moos et al. (Mon,) studied this question.